Estimation of Hydrolysis Rate 

Constants of Carboxylic Acid 

Ester and Phosphate Ester 

Compounds in Aqueous 

Systems from Molecular 

Structure by SPARC

R E S E A R C H A N D D E V E L O P M E N T
EPA/600/R-06/105 

September 2006 

Estimation of Hydrolysis Rate Constants of 

Carboxylic Acid Ester and Phosphate Ester 

Compounds in Aqueous Systems from 

Molecular Structure by SPARC 

By 

S. H. Hilal

Ecosystems Research Division 

National Exposure Research Laboratory 

Athens, Georgia 

U.S. Environmental Protection Agency 

Office of Research and Development 

Washington, DC 20460
NOTICE 

The information in this document has been funded by the United States Environmental 

Protection Agency. It has been subjected to the Agency's peer and administrative review, and 

has been approved for publication. Mention of trade names of commercial products does not 

constitute endorsement or recommendation for use. 

ii 
ABSTRACT 

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity 

models were extended to calculate hydrolysis rate constants for carboxylic acid ester and 

phosphate ester compounds in aqueous non- aqueous and systems strictly from molecular 

structure. The energy differences between the initial state and the transition state for a molecule 

of interest are factored into internal and external mechanistic perturbation components. The 

internal perturbations quantify the interactions of the appended perturber (P) with the reaction 

center (C). These internal perturbations are factored into SPARC’s mechanistic components of 

electrostatic and resonance effects. External perturbations quantify the solute-solvent 

interactions (solvation energy) and are factored into H-bonding, field stabilization and steric 

effects. These models have been tested using 1471 reliable measured base, acid and general 

base-catalyzed carboxylic acid ester hydrolysis rate constants in water and in mixed solvent 

systems at different temperatures. In addition, they were tested on 397 reliably measured second 

order base, acid and general base-catalyzed phosphate ester hydrolysis rate constants over a 

range of temperatures. The RMS deviation error between predicted and measured values for 

carboxylic acid ester and phosphate ester compounds was close to the intralaboratory 

experimental error. 

iii 
EXECUTIVE SUMMARY 

This report is in partial fulfillment of the National Exposure Research Laboratory Task 

number 16386, “Developing Computational Tools for Predicting Chemical Fate, Metabolism, 

and Markers of Exposure”, (Goal 4 and GPRA Sub-objective 4.5.2.) under subtask title 

“Development of computational tools and databases for screening-level modeling of the 

environmental fate of toxic organic chemicals”. The primary goal of this subtask is to develop 

computational tools to predict the identity of chemical species to which vulnerable organisms are 

likely to be exposed. This screening-level model will require a chemical structure as input, and 

will generate a set of daughter products that can form when the chemical is released into the 

environment. 

The subtask is broadly divided into five research areas. The first area focuses on 

speciation of organic chemicals in aquatic systems. The second area focuses on the abiotic 

transformation processes hydrolysis and reduction. The third is concerned with identifying and 

characterizing the state variables that control the rate and extent of transformation processes in 

the environment. The fourth focuses on the refinement and extension of SPARC models. The 

area integrates 'omic tools' into environmental fate research. 

The primary goal of the second research area of this subtask (this project) is to develop 

and implement mathematical models to estimate hydrolysis rate constants of carboxylic acid 

esters and organophosphate ester using SPARC. This report describes the SPARC 

computational modeling approach to estimate hydrolysis rate constants that are necessary to 

predict the environmental fate of carboxylic acid ester and organophosphate ester compounds in 

water. The SPARC chemical reactivity models were extended to calculate hydrolysis rate 

constants for the aforementioned compounds in aqueous and in non-aqueous systems as a 

iv 
function of temperature in basic, acidic and neutral solution media strictly from molecular 

structure. The output from the hydrolysis rate constants models will inform chemists, 

environmentalists and toxicologists as to the chemical forms (parent or transformation products) 

that may be present in an ecosystem and their rates of hydrolysis transformation. The ultimate 

goal of this research project is to extend the SPARC solution-phase hydrolysis model to estimate 

the transformation rates of other chemical compounds classes of concern that may hydrolyze 

under environmental conditions, and to predict all possible hydrolysis pathways in aqueous and 

non-aqueous systems. 

The SPARC chemical hydrolysis models will meet some of the needs of EPA’s long term 

research task agenda under chemical toxicology initiative that emphasizes that EPA will have to 

rely heavily on predictive modeling to carry out the increasingly complex array of exposure and 

risk assessments necessary to develop scientifically defensible regulations. Ultimately, SPARC 

chemical reactivity models (ionization pKa, speciation, tautomerization, chemical hydration and 

chemical hydrolysis) will be integrated with the metabolic simulator TIMES (TIssue 

MEtabolism Simulator) and CATABOL to provide a highly reliable simulator of metabolic 

activity for direct application to the computational toxicology initiative. 

v 
TABLE OF CONTENTS 

ABSTRACT................................................................................................................................... iii 

EXECUTIVE SUMMARY ........................................................................................................... iv 

LIST OF FIGURES ..................................................................................................................... viii 

LIST OF TABLES ...............................................................................................................................ix 

1. GENERAL INTRODUCTION ........................................................................................................1 

2. QUANTITATIVE CHEMICAL THEORY.......................................................................................2 

3. SPARC COMPUTATIONAL PROCEDURE...................................................................................3 

4. CHEMICAL HYDROLYSIS ....................................................................................................4 

4.1. Carboxylic acid Esters and Organophosphorus Hydrolysis

 Mechanisms and Reactions Pathway..................................................................................5 

4.1.1 Carboxylic Acid Esters ................................................................................7 

4.1.1.1. Base Catalyzed Hydrolysis ............................................................7 

4.1.1.2. Acid Catalyzed Hydrolysis .............................................................8 

4.1.1.3. General Base Catalyzed Hydrolysis................................................9 

4.1.2. Phosphate ester (Organophosphorus)................................................................9 

4.1.2.1. Base Catalyzed Hydrolysis ..........................................................10 

4.1.2.2. Acid Catalyzed Hydrolysis ..........................................................11 

4.1.2.3. General Base Catalyzed Hydrolysis ............................................12 

5. HYDROLYSIS MODELING APPROACH...................................................................................14 

5.1. Reference Rate Model................................................................................................16 

5.2. Internal Perturbation Models .....................................................................................16 

5.2.1. Electrostatic Effect ........................................................................................17 

5.2.1.1. Direct Field Effect.........................................................................18 

5.2.1.2. Mesomeric Field Effect.................................................................20 

5.2.1.3. Sigma Induction Effect ................................................................22 

5.2.1.4. Rπ effect........................................................................................23 

5.2.2. Resonance Effect ....................................................................................24 

5.3. External Perturbation (Solvation Effect) Models.............................................................25 

5.3.1. Hydrogen Bonding Effect........................................................................26 

5.3.2. Field Stabilization Effect .........................................................................27 

5.3.3. Steric Effect .............................................................................................28 

5.4. Temperature Effect ....................................................................................................30 

vi 
6. RESULTS AND DISCUSSIONS.............................................................................................31 

7. MODELS VERIFICATION AND VALIDATION..................................................................37 

8. TRAINING AND MODEL PARAMETER INPUT ................................................................39 

9. CONCLUSION..........................................................................................................................95 

10. REFERENCES .......................................................................................................................97 

APPENDIX...........................................................................................................................101 

vii 
LIST OF FIGURES 

Figure 1. The effect of solvent alpha sites on the initial and 

the transition states on hydrolysis rate constants ........................................................27 

Figure 2. Log hydrolysis rate constants vs temperature for alkaline hydrolysis 

of carboxylic acid esters.........................................................................................30 

Figure 3. SPARC-calculated versus observed log hydrolysis rate constants 

for alkaline hydrolysis of carboxylic acid esters ...................................................34 

Figure 4. SPARC-calculated versus observed log hydrolysis rate constants 

for acid hydrolysis of carboxylic acid esters..........................................................35 

Figure 5. SPARC-calculated versus observed log hydrolysis rate constants for 

general alkaline base hydrolysis of carboxylic acid esters .........................................35 

Figure 6. Sample calculation of the log hydrolysis rate constant in acidic media 

for p-nitrophenyl acetate in water at 25o C. .........................................................102 

viii 
LIST OF TABLES 

Table1A. Statistical comparison of SPARC-calculated to observreda values of 

log hydrolysis rate constants of carboxylic acid in water and in mixed 

 solvent systems .....................................................................................................36 

Table1B. Statistical comparison of SPARC-calculated to observed values of log 

hydrolysis rate constants of organophosphorus in water..........................................36 

Table 2. SPARC-calculated vs. observed log base catalyzed hydrolysis rate 

constants for carboxylic acid esters in water ........................................................40 

Table 3. SPARC-calculated vs. observed log base catalyzed hydrolysis rate 

constants for carboxylic acid esters in water-acetone mixtures ............................44 

Table 4. SPARC-calculated vs. observed log base catalyzed hydrolysis rate 

constants for carboxylic acid esters in ethanol-water mixtures .............................48 

Table 5. SPARC-calculated vs. observed log base catalyzed hydrolysis rate constants 

for carboxylic acid esters in methanol-water mixtures..........................................51 

Table 6. SPARC-calculated vs. observed log base catalyzed hydrolysis rate constants 

for carboxylic acid esters in dioxane-water mixtures ............................................55 

Table 7. SPARC-calculated vs. observed log base catalyzed hydrolysis rate constants 

for carboxylic acid esters in acetonitrile-water mixtures ......................................58 

Table 8. SPARC-calculated vs. observed log acid catalyzed hydrolysis rate constants 

for carboxylic acid esters in water ........................................................................59 

Table 9. SPARC-calculated vs. observed log acid catalyzed hydrolysis rate 

constants for carboxylic acid esters in water-acetone mixtures.............................69 

Table 10. SPARC-calculated vs. observed log acid catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-methanol mixtures..........................................74 

Table 11. SPARC-calculated vs. observed log acid catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-ethanol mixtures .............................................75 

Table 12. SPARC-calculated vs. observed log acid catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-dioxane mixtures ...........................................76 

Table 13. SPARC-calculated vs. observed log neutral hydrolysis rate constants for 

carboxylic acid esters in water...............................................................................77 

ix 
Table 14. SPARC-calculated vs. observed log neutral hydrolysis rate constants 

for carboxylic acid esters in water-acetone mixtures.............................................79 

Table 15. SPARC-calculated vs. observed log neutral hydrolysis rate constants for 

carboxylic acid esters in water-ethanol mixtures...................................................82 

Table 16. SPARC-calculated vs. observed log neutral hydrolysis rate constants 

for carboxylic acid esters in water-dioxane mixtures ............................................83 

Table 17. SPARC-calculated vs. observed log hydrolysis rate constants for 

organophosphorus in water in basic media............................................................84 

Table 18. SPARC-calculated vs. observed log acid hydrolysis rate constants for 

organophosphorus in water....................................................................................91 

Table 19. SPARC-calculated vs. observed log neutral hydrolysis rate constants 

For organophosphorus in water .............................................................................93 

x 
1. GENERAL INTRODUCTION 

The major differences among the behavior profiles of organic compounds in the 

environment are attributable to their physicochemical properties. The key properties are believed to 

be vapor pressure, solubility, Henry's constant in water, octanol/water distribution coefficient and 

transportation processes rates/equilibrium constants. Although considerable progress has been 

made in transportation process elucidation and modeling for chemical and physical processes, 

determination of the complete set of values for the fundamental thermodynamic and physicochemical properties have been achieved for only a small number of molecular structures. For most 

chemicals, only fragmentary knowledge exists about those properties that determine their fate in the 

environment. A big gap still exists between the available information and what is needed. 

In fact, physical and chemical properties have only actually been measured for about 1 

percent of the approximately 70,000 industrial chemicals listed by the U.S. Environmental 

Protection Agency's Office of Prevention, Pesticides and Toxic Substances (OPPTS) [1], with 

approximately 1000 new chemicals being added each year. These properties, in most instances, 

must be obtained from measurements or from the judgment of expert chemists. Reliable estimation 

techniques for these properties are therefore very cost-effective. In any case, trained technicians and 

adequate facilities would not be available for measurement efforts involving thousands of 

chemicals. 

Mathematical models for predicting the fate of pollutants in the environment require 

reactivity parameter values--that is, the physical and chemical constants that govern reactivity. 

Although empirical structure-activity relationships (SAR) have been developed that allow 

estimation of some constants, such relationships generally hold only within limited families of 

chemicals. Computer programs have been under development for several years that predict 

1
chemical reactivity parameters such as ionization pKa, electron affinity and numerous physical 

properties strictly from molecular structure for a broad range of molecular structures [2-14]. The 

prototype computer program called SPARC uses computational algorithms based on fundamental 

chemical structure theory to estimate a variety of reactivity parameters. This capability crosses 

chemical family boundaries to cover a broad range of organic compounds. SPARC costs the user 

minimal computer time and will provide greater accuracy and a boarder scope of predicted physical 

and chemical parameters than is possible with other conventional estimation techniques. 

2. QUANTITATIVE CHEMICAL THEORY 

Chemical properties describe molecules in transition, that is, the conversion of a reactant 

molecule to a different state or structure. For a given chemical property, the transition of interest 

may involve electron redistribution within a single molecule or a bimolecular union to form a 

transition state or distinct new product. The behavior of chemicals depends on the differences in 

electronic properties of the initial state of the system and the state of interest. For example, 

chemical equilibrium - thus ionization chemical equilibrium constants - depends on the energy 

differences between the protonated state and unprotonated state. Electron affinity depends on the 

energy differences between the LUMO (Lowest Unoccupied Molecular Orbital) state and the 

HOMO (Highest Unoccupied Molecular Orbital) state of the molecule. Hydrolysis reaction rates, 

on the other hand, depend on the energies of the transition states relative to the reactant (initial) 

states. 

In every case, these differences are usually small compared to the overall energy. The ab 

initio methods that calculate absolute energies have a difficult time in predicting the small energy 

differences between the chemical states of interest. Estimation approaches based on LFER (Linear 

2
Free Energy Relationships), QSAR (Quantitative Structure Activity Relationship) and QSP 

(Quantitative Structure Property) have proven to offer good prediction for a limited number of 

molecules and those within a particular class of molecules, but have failed to predict either chemical 

or physical properties for a board range of molecular structures. In most cases, the number of data 

points/values does not exceed the number of the trainable parameters needed to estimate a property 

of interest by large amount as would be desired. 

Perturbation methods, however, can be used to accurately compute the small differences in 

energy leading to differences in reactivity. These methods treat the final state as a perturbed initial 

state and the energy differences then are determined by quantifying the perturbation. These 

perturbation methods are ideally suited for expert system application due to their extreme flexibility 

and computational simplicity. The requisite conditions for applicability, as well as the selection of 

appropriate reference structures or reactions, can be easily built into the computation control portion 

of the expert system. 

3. SPARC COMPUTATIONAL PROCEDURE 

SPARC does not do "first principles" computation, but seeks to analyze chemical structure 

relative to a specific reactivity query in much the same manner as an expert chemist would do. For 

chemical properties, reaction centers with known intrinsic reactivity are identified and the impact on 

the reactivity of appended molecular structure (termed perturber) is quantified using mechanistic 

perturbation models. For physical properties, molecular structures are broken at each essential 

single bond and a molecular descriptor is expressed as a linear combination of fragment 

contributions of the property of interest. SPARC calculates the molecular descriptors and inserts 

them in to the physical process models developed from intermolecular interaction models to 

calculate a chemical and/or physical property of interest. 

3
The computational approaches in SPARC are a blending of conventional LFER [15-17], 

Structure Activity Relations (SAR) [18, 19] and Perturbed Molecular Orbital (PMO) theory [20, 

21]. In general, SPARC utilizes a classification scheme that defines the role of structural 

constituents in effecting or modifying reactivity, and quantifies the various "mechanistic" 

descriptions commonly utilized in physical analysis, such as resonance, electrostatic, induction 

and dipole effects, etc. SPARC uses LFER to compute thermodynamic or thermal properties and 

PMO theory to describe quantum effects such as delocalization energies or polarizabilities of π

electrons. In reality, every chemical property involves both quantum and thermal contributions 

and necessarily requires the use of both perturbation methods for prediction. 

A "toolbox" of mechanistic perturbation models has been developed that can be 

implemented where needed for a specific reactivity query. Resonance models were developed 

and calibrated on light absorption spectra [1, 22],- whereas electrostatic models were developed 

and calibrated on ionization equilibrium constants [3, 4, 7-9]. Solvation models (e.g., dispersion, 

induction, H-bonding, deipole-dipole) have been developed and calibrated on physical properties 

such as vapor pressure, solubility, distribution coefficient Henry’s law constant and gas 

chromatographic retention time [4, 5, 11, 12]. 

4. CHEMICAL HYDROLYSIS 

Hydrolysis is a chemical transformation process in which an organic compound, RX, 

reacts with water, forming a new carbon-oxygen bond and the cleaving of the carbon-X bond in 

the original molecule. The net reaction is most commonly a direct displacement of X by OH or: 

H2O 

R-OH + X- + H+

 (1) 

4

R-X 
Hydrolysis is likely to be the most important reaction of organic molecules with water in 

aqueous environments and is a significant environmental fate process for many organic 

chemicals. Hydrolysis under environmental conditions is actually not one reaction as shown in 

equation (1), but a family of reactions involving compound types as diverse as alkyl halides, 

carboxylic acid esters, phosphate esters, carbamates, epoxides, nitriles, amides, amines, etc [23]. 

However, many organic compounds have functional groups that are relatively inert with respect 

to chemical hydrolysis, such as alkanes, ethers, aromatic nitro compounds, etc. 

The object of this study is to extend the SPARC chemical reactivity models to estimate 

hydrolysis rate constants for carboxylic acid esters and organophosphorus compounds from 

molecular structure. Based on these models, the chemical forms or species that may be present 

in the ecosystem can be identified (parent compounds such as carboxylic acid 

esters/organophosphorus or hydrolyzed products such as organic acid and alcohol). This report 

describes the process models and rate constants that are necessary to predict the environmental 

fate of these chemicals in the aqueous phase as a function of temperature in basic, acidic and 

neutral (general base) solution media strictly from molecular structure. 

4.1. Carboxylic acid Esters and Organophosphorus Hydrolysis Mechanisms 

and Reactions Pathway 

When an organic molecule undergoes hydrolysis, a nucleophile (H2O, OH -

) attacks an 

electrophile (carbon or phosphorus atom) and displaces a leaving group such as phenoxide. For 

a long time, it has been was recognized that nucleophilic displacement reactions usually fit one 

of two distinct substitution processes: SN1 (Substitution, Nucleophilic, Unimolecular) and SN2 

(Substitution, Nucleophilic, Bimolecular) [24]. Kinetically, the SN1 process is characterized by 

5
A rate independent of the concentration and nature of the nucleophile, the formation of racemic 

products from optically active parent chemicals, and enhancement of the rate due to an electrondonating substituent on the central atom. The rate determining step is the ionization of the RX to 

yield a planar carbonium ion (equation 2a), that then undergoes a relatively rapid nucleophilic 

attack as shown in equation 2b. 

slow (2 a) RX R+ + XROH + H+ (2b) R+ + H2O 

fast 

In an SN2 process, on the other hand, the rate depends on the concentration and type of the 

nucleophile, and an optically active starting material yields gives a product of inverted 

configuration. This is a one-step bimolecular process involving nucleophilic attack on the 

central atom at the side opposite the leaving group: 

- H [ H2O ---R----X] 2O + R X H+ + HO R + X ( 3) 

Generally, the hydrolysis of carboxylic acid esters and organophosphorus compounds involves 

bimolecular nucleophilic attack analogous to the SN2 (rather than SN1) mechanism on the 

saturated carbon. Organophosphate and carboxylic acid esters, depending on the substituents 

and the local environmental conditions, can undergo acid catalyzed hydrolysis, second-order 

alkaline hydrolysis, and neutral hydrolysis (general base). The alkaline and neutral hydrolysis 

pathways may not give the same products depending on the structure of the ester groups [25]. 

This is because hydroxide is about 108 times better as a nucleophile than water towards the 

phosphorous atom but only 104

 times better as a nucleophile towards saturated carbon [25]. 

6
4.1.1. Carboxylic Acid Esters 

Ester functions are among the most common acid derivatives present in natural as well as 

man-made chemicals (e.g., lipids, plasticizers, pesticides). An ester bond is defined as 

ROC(=O)-, where R is a carbon-centered substituent. The general structure of carboxylic acid 

esters is represented by R1C(=O)OR2, where R1 and R2 are appended perturber structures. These 

perturbers can be alkyl chains, phenyl groups or heteroatoms. Carboxylic acid esters are used 

industrially to make flavors, soaps, herbicides and so on. Generally hydrolysis of an ester bond 

yields the corresponding acid and alcohols. Carboxylic acid esters undergo hydrolysis through 

three different mechanisms: base, acid and general base-catalyzed (neutral) hydrolysis. 

4.1.1.1. Base Catalyzed Hydrolysis 

The base-catalyzed or alkaline hydrolysis of esters generally takes place via a BAC2 

mechanism as shown in the following equation [26, 27]. BAC2 stands for base-catalyzed, acyloxygen fission, bimolecular reaction. It is similar to the SN2 reaction, occurring when the 

hydroxide ion attacks the carbonyl carbon of an ester to yield a carboxylic acid and an alcohol. 

Alkaline hydrolysis of esters also occurs through other mechanisms, e.g., BAC1 (base-catalyzed, 

acyl-oxygen fission, unimolecular), BAL1 (base-catalyzed, alkyloxygen fission, unimolecular) and 

BAL2 (base-catalyzed, alkyl-oxygen fission, bimolecular). However, BAC2 is the most common 

mechanism, and usually masks all other possible mechanisms. 

7
O R1 O- R1 OH2O 

C CH R1COOH + R2OH + OHC OR2 

H R + 1 OR2 HO -O 

OHOR2

­

4.1.1.2. Acid Catalyzed Hydrolysis 

Acid catalyzed hydrolysis of esters takes place via an AAC2 mechanism as shown in the 

following equation [26, 27]. AAC2 stands for acid-catalyzed, acyl-oxygen fission, bimolecular 

reaction. It is similar to the SN2 reaction, occurring when a positive hydrogen ion catalyzes the 

ester and a water molecule attacks the carbonyl carbon of the ester to produce a carboxylic acid 

and an alcohol. Acid-catalyzed hydrolysis of esters also takes place by other mechanisms, such 

as AAC1 (acid-catalyzed, acyl-oxygen fission, unimolecular), AAL1 (acid-catalyzed, alkyl-oxygen 

fission, unimolecular) and AAL2 (acid-catalyzed, alkyl-oxygen fission, bimolecular) [26, 27]. 

However, AAC2 is the general mechanism for acid-catalyzed hydrolysis of esters, and usually 

masks all other possible mechanisms. 

OH H OH

O H+

H 

R1 C O R1 C O R1COOH + R2OH + H+ 

C 

R1 OR2 OR2 H OR2 

H 

8
4.1.1.3. General Base Catalyzed Hydrolysis 

The general base-catalyzed hydrolysis of esters takes place via a BAC2 mechanism illustrated 

in the following reaction [26, 27]: 

O OO 

C BH

OR R1COOH + R2OH + B: 2 R1 

C

R C 1 OR2 

H O + R1 O- OH 

H H 

OR2

­

B: 

As before, BAC2 stands for base-catalyzed, acyl-oxygen fission, bimolecular reaction. It is also 

similar to the SN2 reaction, occurring when a base (B:) present extracts a hydrogen atom from a 

water molecule, releasing the hydroxide ion, that eventually attacks the carbonyl carbon of the ester 

to yield a carboxylic acid and an alcohol. The base, B: stands for any base, such as ammonia, 

acetate ion, pyridine, imidazole and so on. In the case of neutral hydrolysis, B: represents the water 

molecule. 

4.1.2. Phosphate ester (Organophosphorus) 

Organophosphorus compounds are of interest to many groups of chemists. Biochemists 

study their relationship to cholinesterase inhibition [28] ; organic chemists investigate the 

reaction mechanisms to improve synthetic routes to these chemicals [29]; environmental 

chemists are interested in these compounds for their role a pesticides, as well as their persistence 

and overall toxicity in the environment [25]. These compounds are widely used as insecticides 

for different types of cultivation and for elimination of crustaceans and mosquitoes [30]. Also, 

they are widely used in heavy industries as hydraulic fluid additives, and in the petrochemical 

9
industry as plasticizers [31]. Despite the extensive production and resultant widespread exposure 

of environmental compartments to various amounts of these compounds, surprisingly few 

quantitative data on their hydrolytic reactivity are reported in the open literature. This lack of 

information is particularly surprising because hydrolytic transformation is proposed as an 

important pathway for the degradation of these compounds in aquatic ecosystems [32]. 

Organophosphorus or phosphate esters can be represented as R1OP(=O)(R2)(R3), where 

the oxygen of OR1 is bonded to a sp2 or sp3 carbon (R1). R2 and R3 represent additional leaving 

groups or substituents of the perturber structure, P. Depending on the local environment, these 

compounds hydrolyze via three distinct mechanisms: acid, base and neutral hydrolysis [25, 29]. 

4.1.2.1. Base Catalyzed Hydrolysis 

The base-catalyzed (alkaline) hydrolysis of phosphate esters follows the same general 

mechanism as carboxylic acid ester base hydrolysis, see section 4.1.1.1. This mechanism is 

depicted in the following [14, 29]. BP2 stands for base-catalyzed, phosphoyl-oxygen fission, 

bimolecular reaction, and is similar to the SN2 reaction that occurs when a hydroxide ion attacks 

the carbonyl carbon of an ester to yield a carboxylic acid and an alcohol. 

HOO OO- R2 

O 

- R1 HO P OR2 O P 

R3 

P 

OR2 R3 R1 

H 

R1 + 

R3 

H2O 

O 

R2OH + OH- + R3 P 

R1 

OH 

10
The hydroxide ion attacks the phosphorus atom in the rate-controlling step of the 

sequence [29]. Formation of an intermediate addition product of hydroxide ion and the ester that 

is in equilibrium with the reactants and decomposes to give the products is excluded by the 

failure of the phosphorus group to exchange oxygen with the solvent prior to chemical 

hydrolysis. Therefore, the reaction cannot, proceed by an addition-elimination sequence 

analogous to that believed to represent the course of hydrolysis of carboxylic acid esters, but 

must consist either of a one-step process in which the leaving group is being expelled at the same 

time the substituent group is entering (see the above mechanism), or a two step process in which 

the intermediate decomposes so very rapidly that it cannot equilibrate with the solvent [33, 34]. 

Alkaline hydrolysis of phosphate esters also occurs through other mechanisms, such as: 

BP1 (base-catalyzed, phosphoryl-oxygen fission, unimolecular), BAL1 (base-catalyzed, alkyloxygen fission, unimolecular), and BAL2 (base-catalyzed, alkyl-oxygen fission, bimolecular). 

However, the BP2 mechanism usually dominates and these other mechanisms are masked. In 

certain circumstances, such as when carbonyl or glycerol groups are attached to the molecule, 

there is no dominant pathway; this situation makes it difficult to accurately assess the rate of 

hydrolysis [35, 36]. Since the SPARC model was not designed to model these later situations, 

molecules with these types of mechanisms have not been investigated. 

4.1.2.2. Acid Catalyzed Hydrolysis 

Acid-catalyzed hydrolysis of phosphoric acid esters can occur by direct nucleophilic 

attack at the phosphorus atom without the formation of a pentavalent intermediate. The reaction 

takes place via an AAC2 mechanism as shown in the following equation. AAC2 stands for acidcatalyzed, acyl-oxygen fission, bimolecular reaction. It is similar to the SN2 reaction, occurring 

11
when a positive hydrogen ion catalyzes the ester and a water molecule attacks the carbonyl 

carbon of the ester to produce a carboxylic acid and an alcohol. Acid-catalyzed hydrolysis of 

esters also takes place by other mechanisms such as phosphoryl-oxygen or alkyl-oxygen fission 

unimolecular and alkyl-oxygen fission bimolecular [26, 27]. However, AAC2 is the general 

mechanism for acid-catalyzed hydrolysis of esters and usually masks all other possible 

mechanisms. 

H 

OH O

H+ 

O 

H 

P 

O

R3 

R3 R3 O R3

P 

R2 R2

O OH 

R P 1OH + R3 P + 

OH R3 OH 

R2 R2 

4.1.2.3. General Base Catalyzed (Neutral) Hydrolysis 

Neutral hydrolysis of phosphoric acid esters occurs by direct nucleophilic substitution 

of water at the carbon atom, causing C-O cleavage, , as is the case for trialkyl phosphates such as 

trimethyl phosphate: 

12
O 

O 

R1CH2O P 

+ HOCH2R3 + H+ 

O CH2R3 R1CH2O P 

R2CH2O H O

R2CH2O

O 

H 

This reaction is analogous to the base catalyzed SN2 reaction; however neutral and base 

hydrolysis may not yield the same products. This difference in products is primarily because 

toward phosphorous, OH−

 is a better nucleophile than H2O by about a factor of 108 [37]. This 

usually causes the base catalyzed reaction to occur at the phosphorous atom with the hydroxide 

causing the best leaving group to dissociate (P-O cleavage). However, depending on the leaving 

groups present, the neutral (general base) reaction may occur where water acts as the 

nucleophilic substituent at the carbon atom (C-O cleavage). If a good leaving group is present, 

the reaction may proceed simultaneously by both neutral and base hydrolysis reaction 

mechanisms with C-O and P-O cleavage. Multiple researchers [38] have found higher 

temperatures cause the proportion of C-O to P-O cleavage to be greater; while at lower 

temperatures, P-O cleavage dominates. For example, at 70oC and pH = 5.9 parathion reacted 

90% by C-O cleavage, while at a lower temperature, higher proportion of the neutral reaction 

occurred by P-O cleavage [39]. This observation is explained because the reaction involving CO cleavage requires a greater activation energy than that involving P-O cleavage [40]. Even this 

simple thermal case demonstrates the complexity of the mechanisms involved when dealing with 

phosphoric acid derivatives. 

13
5. HYDROLYSIS MODELING APPROACH 

 Hydrolysis reaction kinetics have been quantitatively modeled within the chemical 

equilibrium framework described in previous publications for ionization pKa in water [3, 6-9]. 

For this, it was assumed that a reaction rate constant could be described in terms of a pseudo 

equilibrium constant between the reactant (initial) and transition (final) states of the molecule 

undergoing hydrolysis. This reaction rate constant is expressed in the appropriate second order 

form inclusive of catalytic effects. For molecules susceptible to hydrolysis, reaction centers with 

known intrinsic reactivity were identified and the reaction rate constants expressed (energy 

terms) by perturbation theory as: 

log kHydrolysis = log kc + Δ log kc 

 (4) p 

where log kHydrolysis is the log hydrolysis rate constant of interest and log kc is the log of the 

intrinsic rate constant of the reaction center. A given reaction center may have two or more 

appendages or perturbing units. For example, a carboxylic acid ester reaction center has two 

appendages and a phosphate ester has three. The log kc for the reaction center can be either 

measured directly (if the reaction center exists as a distinct molecule) or determined via data-fit. 

The Δp log kc term denotes the perturbations of the intrinsic rate constant of the reaction center 

due to the appended structures, P, and to solvation effects. The perturbations associated with 

appendages to the reaction center are factored into the mechanistic components of resonance and 

electrostatic effects. Likewise, the perturbations associated with the solvent are factored into 

steric, H-bonding, and field stabilization effects. The solvent dependence of log kc is expressed 

as a linear function of solvent properties (alpha/beta H-bonding and dipole; calculated as 

described later) with data-fitted coefficients. For mixed solvents, solvent descriptors that are site 

interactions, such as H- bonding, are the mole-fraction-weighted average when used in the 

14
interaction models, and the interactions are summed over all solvent components [11]. Solvent 

properties that are essentially bulk in nature, such as the dielectricity, volume, and polarizability, 

are volume-fraction-averaged [11]. With the exception of steric effects, all the perturbations of 

the reaction center are modeled independently and simply summed. 

The SPARC computational model for the hydrolysis rate constant is divided into three 

sub-models: reference rate, internal perturbation, and external perturbation. The reference rate 

sub-model calculates the hydrolysis rate constant for the smallest ester compound substructure 

that excludes internal perturbation and steric effects. The internal perturbation model calculates 

the perturbation of the reference hydrolysis rate constant due to the internal perturbation 

interactions between the reaction center and its appended perturber. Finally, the external 

perturbation model calculates the solvation contributions to changes in the hydrolysis rate 

constant due to solute-solvent interactions. The hydrolysis rate constant contributions from these 

three sub-models are then summed to give the total calculated hydrolysis rate constant for the 

compound under investigation according to equation: 

log kHydrolysis = log kc + δIP log kc 

+ δEP log kc 

(5) 

where log kc describes the hydrolysis behavior of the reaction center (reference structure), i.e., 

the “reference rate”, in this study the hydrolysis rate constant for the smallest ester compound 

structure that resemble the structure of the reaction center C(=O)OCH3 or P(=O)OCH3. The 

term, δIP log kc is the change in hydrolysis behavior of the reaction center brought about by 

internal interactions due to the perturber structure, P. SPARC computes the various internal 

reactivity perturbations, δIP log kc, used to "correct" the hydrolysis behavior of the reaction center 

(reference structure) for the compound in question in terms of all the potential "mechanisms" for 

the interaction of the perturber structure, P, of the compound and its reaction center (reference 

15
structure), C [3, 4, 6-9]. The last term in equation 5 describes the external perturbation of the 

hydrolysis rate due to the effect of the solvent on both the initial (reactant) and the final 

(transition) state. Specifically, δEP log kc describes the change in the solvation of the initial state 

versus the transition state due to steric, H-bond, and field stabilization effects of the solvent. 

5.1. Reference Rate Model 

As stated earlier, the reference rate, log kc, is the hydrolysis rate constant for the smallest 

ester compound that resembles the structure of reaction center C(=O)OR or P(=O)OR (in this 

study). The reference rate is free of any internal perturbation interactions, such as resonance, 

electrostatic and steric effects. However, it is dependent upon the temperature. As the 

temperature increases, the reference hydrolysis rate increases. SPARC expresses the reference 

rate, log kc, as a function of the temperature and enthalpic and entropic contributions as 

log kc = A + logTk + Ref1 + Ref2/Tk (6) 

where A is the log of the Arrhenius equation pre-exponential factor, Tk is the temperature in 

degrees Kelvin, Ref1 is the entropic contribution to the rate, and Ref2 is the enthalpic 

contribution. A, Ref1, and Ref2 are all data-fitted parameters that are the same for all molecules, 

solvents, and temperatures. 

5.2. Internal Perturbation Models 

The internal perturbation of the hydrolysis rate constant of the reaction center (reference 

structure) in equation (5) for a molecule of interest can be expressed in terms of mechanistic 

perturbations as: 

16
δIP log kc = δres log kc + δelec log kc 

 (7) 

where the δres logkc and δelec logkc describe the change in the hydrolysis rate due to the difference 

in the resonance and electrostatic interactions of P with the initial state versus the transition state 

(activation energy) of C, respectively. Electrostatic interactions are derived from local dipoles or 

charges in P interacting with charges or dipoles in C. The term, δres logkc describes the effect on 

the rate due to a change in the delocalization of π-electrons of the two states due to P. The 

delocalization of π electrons can be into or out of the reaction center. 

The modeling of the perturber effects on chemical reactivity relates to the structural 

representation S-R-C, where S-R is the perturber structure, P, appended to the reaction center, C. 

S denotes a substituent group that "instigates" the perturbation. For electrostatic effects, S 

contains (or can induce) electric fields; for resonance, S donates/receives electrons to/from the 

reaction center. R links the substituent and reaction center and serves as a conductor of the 

perturbation (e.g., "conducts" resonant π electrons or electric fields) [2-4, 7]. 

5.2.1. Electrostatic Effect 

Electrostatic effects on reactivity derive from charges or electric dipoles in the appended 

perturber structure, P, interacting through space with charges or dipoles in the reaction center, C. 

Direct electrostatic interaction effects (field effects) are manifested by a fixed charge or dipole in 

a substituent interacting through the intervening molecular cavity with a charge or dipole in the 

reaction center. The substituent can also "induce" electric fields in R that can interact 

electrostatically with C. This indirect interaction is called the "mesomeric field effect". In 

addition, electrostatic effects derived from electronegativity differences between the reaction 

center and the substituent are termed sigma induction (or Rπ if π-electrons involves). These 

17
effects are transmitted progressively through a chain of σ-bonds (or π) bonds between atoms. 

For compounds containing multiple substituents, electrostatic perturbations are computed for 

each singly and summed to produce the total effect. 

5.2.1.1. Direct Field Effect 

For a given dipolar or charged substituent interacting with the change in the charge at the 

reaction center, the direct field effect is expressed as a multipole expansion 

δ qq δ q μ cosθ δ μ q cos θ δ μ μ cosθ / cos θ Δ cs c s cs c s cs c s cs cs δ( E ) (8) field = / + 2 + /2 + 3 + ........

r Dcs e rcs De r Dcs e rD cs e

where qs is the charge on the substituent, approximated as a point charge located at point, s/; μs is 

the substituent dipole located at point s (this dipole includes any polarization of the anchor atom i 

effected by S); qc (δμc) is the change in charge (dipole moment) of the reaction center 

accompanying the reaction, both presumed to be located at point c; θ gives the orientation of the 

substituent dipole relative to the reaction center; De is the effective dielectric constant for the 

medium; and rcs (rcs

/

) is the distance from the substituent dipole (charge) center to the reaction 

center. 

In modeling electrostatic effects, only those terms containing the "leading" nonzero 

electric field change in the reaction center are retained. For example, acid-base ionization is a 

monopole reaction that is described by the first two terms of the preceding equation; electron 

affinity is described by only the second term, whereas the dipole change in hydrolysis rate 

constant or H-bond formation is described by the third and fourth terms. 

18
In order to provide parameter "portability" and, hence, effects-model portability to other 

structures and to other types of chemical reactivity, the contribution of each structural component 

is quantified independently: 

elec s cs δfield log kc = ρelec σp = ρelec σcs FS = ρ F

3 

cos θ (9) 

rcs De 

where σp characterizes the field strength that the perturber exerts on the reaction center and has 

been previously calculated for estimation of ionization pKa [2-4, 7]. ρele is the susceptibility of a 

given reaction center to electric field effects that describes the electrostatic change 

accompanying the hydrolysis rate constant reaction. ρele is presumed to be independent of the 

perturber. The perturber potential, σp, is further factored into a field strength parameter, F 

(characterizing the magnitude of the field component, charge or dipole, on the substituent), and a 

conduction descriptor, σcs, of the intervening molecular network for electrostatic interactions. 

This structure-function specification and subsequent parameterization of individual component 

contributions enables one to analyze a given molecular structure (containing an arbitrary 

assemblage of functional elements) and to "piece together" the appropriate component 

contributions to give the resultant reactivity effect. 

The electrostatic susceptibility, ρele, is a data-fitted parameter inferred directly from 

measured hydrolysis rate constants. This parameter is determined once for each reaction center 

and stored in the SPARC database. With regard to the substituent parameters, each uncharged 

substituent has one field strength parameter, Fμ, characterizing the dipole field strength; whereas, 

a charged substituent has two, Fq and Fμ. Fq characterizes the effective charge on the substituent 

and Fμ describes the effective substituent dipole inclusive of the anchor atom i, assumed to be a 

19
carbon atom. If the anchor atom i, is a noncarbon atom, then Fμ is adjusted based on the 

electronegativity of the anchor atom relative to carbon. The effective dielectric constant, De, for 

the molecular cavity, any polarization of the anchor atom i affected by S, and any unit 

conversion factors for charges, angles, distances, etc. are included in the F's. 

Since the transition states for both base and general base-catalyzed hydrolysis of the 

reaction center are negatively charged, the substituent dipole will increase the hydrolysis rate 

constant of these reactions. In contrast, the transition state for acid hydrolysis of carboxylic acid 

esters and organophosphorus is positively charged, and the substituent dipole will decrease the 

hydrolysis rate constant. For example, the direct field contribution is 0.32 and -0.042 log-units 

for base and acid catalyzed hydrolysis of ethyl p-nitrobenzoate respectively, while it is 0.346 logunit for general base catalyzed hydrolysis of p-nitrophenyl acetate. Since the transition states of 

the base and general base catalyzed hydrolysis of esters are negative, the field always contributes 

positively to the internal perturbations causing the hydrolysis rate constant to increase. In 

contrast, the field contributes negatively to the internal perturbations for acid catalyzed 

hydrolysis because of the positive transition state that occurs during the hydrolysis reaction 

causing the hydrolysis rate constant to decrease. 

5.2.1.2. Mesomeric Field Effect 

A mesomeric field, MF, (π-induction or indirect field) is generated when either an 

electron withdrawing or electron donating substituent induces electric fields or charges on the 

molecular conductor R that can interact electrostatically with the reaction center, C. An electronwithdrawing substituent creates positive charges on the conductor, while an electron-donating 

substituent creates negative charges. Since the transition states in both base and general base20
catalyzed hydrolysis of carboxylic acid and phosphate esters are negatively charged, the 

electron-withdrawing substituents will increase the hydrolysis rate constant because the induced 

positive charges on the molecular conductor will stabilize the negative charges of the reaction 

center. However, electron-donating substituents induce negative charges on the molecular 

conductor and have an opposite effect on the hydrolysis rate constant. 

In SPARC, this mesomeric field effect (π-induction or indirect field) is treated as a 

collection of discrete charges, qR, with the contribution of each described by the following 

equation. The MF effect on the log of the hydrolysis rate constant due to either the electronwithdrawing or electron-donating substituents is given as 

= ik δMF log kc ρelec MFS ∑q

2 AMF 

(10) 

k rkc 

where as before, ρelec is the intrinsic susceptibility of the reference reaction center to electrostatic 

effects independent of the substituent; MFS is the mesomeric field constant of the substituent that 

describes its ability to induce charges on the molecular conductor, R, and generate the 

mesomeric field. MFS gauges the ability or strength of a given S to induce a field in Rπ. It 

describes the π-induction ability of a particular substituent relative to the CH2

-

. AMF is a datafitted parameter and has the same value for all molecules in this study. Substituent MFS values 

have been calculated and presented in previous work [4]; qik is the charge induced at atom k in R 

calculated using PMO (Perturbed Molecular Orbital) theory [4, 20, 21] ;and rkc is the throughcavity distance between the charge on atom k and C. 

21
An electron-withdrawing substituent creates positive charges on the conductor, while an 

electron-donating substituent creates negative charges. Since the transition states in both base 

and general base-catalyzed hydrolysis of carboxylic acid and phosphate esters are negatively 

charged, the electron-withdrawing substituents will increase the hydrolysis rate constant because 

the induced positive charges on the molecular conductor will stabilize the negative charges of the 

reaction center. However, electron-donating substituents induce negative charges on the 

molecular conductor and have an opposite effect on the hydrolysis rate constant. For example, 

the mesomeric field (MF) contribution is 0.65 and 0.147 log-units for hydrolysis of ethyl pnitrobenzoate in base and acid catalyzed media respectively and it is 0.513 log unit for hydrolysis 

of p-nitrophenyl acetate in general base catalyzed medium. The MF contributions are positive in 

all three catalyzed media and increase the hydrolysis rate constant because the induced positive 

charges on the phenyl ring stabilize the charged transition states. In addition, we see large 

positive values for the base and general base catalyzed hydrolysis because of the negative 

transition states that occur during the hydrolysis reactions for these mechanisms. The induced 

positive charges on the phenyl ring enhance the stabilization of the negative transition states 

more. In contrast, the small positive value for acid catalyzed hydrolysis is due to the positive 

transition state that occurs during the hydrolysis reaction and diminishing stabilization of it. 

5.2.1.3. Sigma Induction Effect 

Sigma induction occurs due to the difference in electronegativity between C and S. For 

base and general base-catalyzed hydrolysis of carboxylic acid and phosphate esters, the reaction 

center has a large electronegativity. Therefore, methyl substituents, for example, will move 

charge or electrons into the reaction center and decrease the hydrolysis rate constant. The acid 

22
hydrolysis reaction center is less electronegative and the substituent-induced perturbations are 

always quite small. Sigma induction is a short range effect. Calculated effects due to 

substituents beyond two atoms from C were considered negligible. The sigma induction effects 

are given as: 

δ log k = ρ ∑ (χc −χ ) NB (11) Sigma c elec s 

where χc and χs are the electronegativities of the reaction center and the appended substituent, 

respectively, and NB is a data-fitted parameter that depends on the number of appended 

substituents. Values of χs and NB have been calculated using ionization pKa data [4, 7]. 

5.2.1.4. Rπ effect 

The Rπ effect is similar to sigma induction, except that it involves π-electrons instead of 

σ-electrons. The magnitude of the reactivity perturbation, δπ log kc, depends upon the difference 

in the electronegativity of the substituent atom π group and that of the reaction center to which it 

is attached. Since the differential induction capability of carboxylic acid and phosphate esters is 

highly correlated with ρelec, SPARC uses a simple model, requiring a minimum of computation 

and only one extra parameter to estimate the Rπ effect on the hydrolysis rate constant as follows: 

δπ log kc = ρelec Pjc σπ (12) 

where Pjc = cos2

Θjc, Θ jc is the dihedral angle of C and R-π unit (describing the π orbital 

alignment), and is set to 1 for this study. σπ is a data-fitted parameter; currently σπ is 0.008 and 

0.1 for aromatic and ethylenic R-π units, respectively. When an R-π unit is attached to a 

carbonyl carbon or P=O (electron withdrawing group), the Rπ effect contributes negatively or 

23
lowers the hydrolysis rate constant. In contrast, when the π-system is attached to an acyl oxygen 

(electron donating group), the Rπ effect increases the hydrolysis rate constant. 

5.2.2. Resonance Effect 

Resonance is a phenomenon of π-electrons moving in or out of the reaction center. 

Resonance stabilization energy in SPARC is a differential quantity, related directly to the extent 

of electron delocalization in the initial state versus the transition state of the reaction center. The 

π-electron source, or sink, in P may be either from a substituent, S, or R-π units contiguous to the 

reaction center. Substituents that withdraw electrons from a reference point, CH2

-

, are 

designated S+ and those that donate electrons are designated S-. The R-π units can either 

withdraw or donate electrons or may serve as "conductors" of π-electrons between resonance 

units. Reaction centers are likewise classified as C+ (C=O or P=O) and C- (alkyl oxygen), 

denoting the withdrawing and donating of electrons, respectively. The distribution of NBMO 

(Non-Bonded Molecular Orbital) charge from the surrogate donor, CH2

-

, is used to quantify the 

acceptor potential for P, the perturber structure [4, 20, 21]. The resonance reactivity perturbation 

is given by: 

' ' δ log k =ρ Δq + ρ Δq (13) res c res c res c 

where ρres and ρ’

res are the susceptibilities of the alkyloxygen (donating electrons) and C=O/P=O 

(withdrawing electrons), respectively, of the ester to resonance interactions. ρres (ρ’

res) quantifies 

the differential “donor” ability of the initial and transition states of the alkyl oxygen (C=O and 

P=O) of the reaction center relative to CH2

-

. Δqc (Δq’

c) is the fraction loss of NBMO charge from 

the alkyl oxygen (C=O or P=O) surrogate reaction center calculated based on PMO theory [4, 

24
21]. Resonance plays different roles in carboxylic acid ester and organophosphorus hydrolysis. 

The major impact is that of resonance stabilization of the leaving group. Thus, the R-π unit 

attached to the oxygen of the ester (alkyl oxygen) reaction center has a pronounced effect, greatly 

increasing the hydrolysis rate constant. Conversely, the R-π unit attached to the C=O or P=O 

(electron-withdrawing group) tends to destabilize the leaving group, thereby decreasing the 

hydrolysis rate constant. 

5.3. External Perturbation (Solvation Effect) Model 

Hydrolysis reactions (involve reactants, intermediates and/or products), are affected by 

changes in the solvating power of the reaction medium. The presence of organic solvents can 

affect the solvating power and thus alter the hydrolysis rate. The presence of water as solvent 

influences the rate and mechanism of hydrolysis reactions in a number of ways; as a nucleophilic 

reagent, as a high dielectric-constant continuum in which reaction takes place; and as a specific 

solvating agent for organic reactants and products (leaving group). 

The external reactivity perturbation (solvation effects) model, i.e., for δEP log kc, 

describes the hydrogen bonding, dielectric field stabilization and steric effects of the solvent on 

the transition (final) state versus the reactant (initial) state of the molecule. The hydrogen 

bonding calculation gauges both the hydrogen acceptor effect (alpha) and hydrogen donor effect 

(beta) of the esters, while the field stabilization calculation describes the effect of dielectric 

constant of the solvent on the ester hydrolysis rate constant. 

25
5.3.1. Hydrogen Bonding Effect 

The hydrogen bonding interaction is a direct, site-coupling of a proton-donating site of 

one molecule with a proton-accepting site of another molecule. The total H-bonding energy is 

resolved into a proton-donating site, α, and proton-accepting site, β that in the SPARC models 

are presumed to be independently quantifiable [4, 6-9]. If the transition state of the ester is 

better solvated or stabilized by the H-bonding than the initial state, the hydrolysis rate constant 

increases. The negatively charged transition states of base and general base-catalyzed ester 

hydrolysis are strongly stabilized by solvent alpha sites, while the solvent beta sites play a minor 

role. Thus, it might appear that α the sites of the solvent should increase carboxylic acid and 

phosphate esters hydrolysis rate constants. However, the α sites do not only solvate the 

transition states, but also the attacking hydroxide ion. The latter tends to stabilize the initial state 

more than the transition state as shown in Figure 1. The net effect is that the solvent α sites tend 

to decrease the carboxylic acid and phosphate esters hydrolysis rate constants. On the other 

hand, the β site of the solvent can interact with an α site, freeing-up hydroxide ions to react with 

an ester thereby tending to increase the base and neutral hydrolysis rate constant. For acidcatalyzed carboxylic acid and phosphate esters hydrolysis, both the α and the β sites of the 

solvent stabilize the initial state more than the transition state. Therefore, both solvent site types 

decrease the acid-catalyzed hydrolysis rate constant. SPARC expresses the alpha and beta site 

H-bond contribution as: 

ρA α ρB β alpha = beta = (14) 

Tk Tk 

where alpha (beta) is the hydrogen accepter (donor) effect of the solute ester and α (β) is the 

hydrogen donating (accepting) value of the solvent. ρA and ρB are data-fitted parameters 

26
quantifying the susceptibility of the α and β values of the solvent, respectively. Tk is the 

temperature in degrees Kelvin. Both α and β of the solvent are calculated as pseudo pKa's, with the 

electrostatic component treated as a dipole transition [4, 7, 11, 12]. 

Figure 1. The effect of solvent alpha sites on the initial and transition states in carboxylic acid ester or 

phosphate ester hydrolysis rate. The alpha sites solvate the hydroxide ion and stabilize the initial state more 

than the transition state. As a result, the alphas decrease the hydrolysis rate constant during ester hydrolysis. 

5.3.2. Field Stabilization Effect 

The field stabilization effect describes the perturbation of the log of the hydrolysis rate 

constant by dielectric stabilization of the transition state by the solvent. It is expressed as a 

function of both the temperature of reaction and the dielectric constant of the solvent: 

ρ FS = FS (15) 

T k D e 

27
where De is the nonlinear temperature dielectric constant of the solvent, and ρFS is the intrinsic 

susceptibility of the hydrolysis rate constant to the solvation effect due to the dielectric properties 

of the solvent, and is a data-fitted parameter. It describes the susceptibility of the transition state 

to dielectric stabilization. Equation 15 quantifies the differential solvation of initial (reactant) 

versus the transition states of the reactants in the hydrolysis reaction due to the dielectric 

constant of the solvent. The dielectric constant of solvents solvates or stabilizes the initial state 

of ester hydrolysis reactants more than the transition states. Thus, the field stabilization effect 

always decreases the hydrolysis rate constant. Comparing the dielectric effect on the ester 

hydrolysis rate constant in various mixed solvents, we observe that the decrease in the rate 

constant is less in pure water than in mixed aqueous-organic solvents. This is because to the 

higher dielectric of pure water compared to the organic solvent component of the mixed solvent 

relatively enhances the stability of the transition state. Thus, the hydrolysis rate constant 

reduction is greater in mixed aqueous-organic solvents. 

For example, The field stabilization effects are –2.843 and –0.297 log-units for 

hydrolysis of ethyl p-nitrobenzoate in base and acid media respectively, while it is –4.530 logunits for hydrolysis of p-nitrophenyl acetate in general base catalyzed medium. The field 

stabilization effect involves the dielectric constant of the solvent and in general it rises 

the energy of the transition state more than the initial state. As a result, it lowers the 

hydrolysis rate constant [41]. 

5.3.3. Steric Effect 

The normal trend for a steric effect is as the bulkiness of the substituent increases, the steric 

effect also increases. Thus, the steric effect always decreases the hydrolysis rate constant. 

28
Comparing the relative steric effect on carboxylic acid ester or phosphate ester hydrolysis rate 

constant for various solvents, we observe there is much less steric effect in pure water than in 

mixed solvents. The reason for this is that pure water more efficiently solvates the solute 

molecule and aligns the structure of the solute ester for the attacking hydroxide ion or water 

molecule. Conversely, the mixed-organic aqueous solvents only partially solvate the solute 

molecule and deform the ester structure, creating a hindrance to attack from the hydroxide ion or 

water molecule. Thus, the reaction does not proceed as rapidly as it does in pure water, and the 

hydrolysis rate constant decreases. Steric effects include both steric blockage of reaction site 

access and strain in achieving the transition state. SPARC expresses the steric effect on the log 

hydrolysis rate constant as: 

s ex thresh Steric = ρ steric 

(

V +V −V ) (16) 

T k D e 

where: Vs is the sum of the appended substituent sizes, Vthresh is a threshold size for onset of 

steric effects; Vex is the excluded (cavity) volume between pairs of appended substituents; ρsteric 

is the intrinsic steric susceptibility, and De is the dielectric constant of the solvent. 

For example, The steric effects are –1.29 and –1.5 log-units for hydrolysis of ethyl 

pnitrobenzoate in base and acid media respectively and it is -0.781 log-unit for neutral hydrolysis 

of p-nitrophenyl acetate. The normal trend of steric effect is that bulkier the substituents lower 

the hydrolysis rate constants. Since both ethyl p-nitrobenzoate and p-nitrophenyl acetate have 

bulky phenyl rings, the steric effects display huge negative values [41]. 

29
5.4. Temperature Effect 

The quantitative relationship between the rate constant and temperature is frequently 

expressed by the Arrhenius equation as: 

k A e

−

⎝

⎜

⎜

⎛ E a 

⎠

⎟

⎞

= RT ⎟ (17) 

where k is the hydrolysis rate constant, A is the pre-exponential or frequency factor, Ea is the 

activation energy (the minimum energy required to form a product from the reactants), R, is the 

gas constant, and T is the absolute temperature in degrees Kelvin. This temperature dependence 

relationship is incorporated in the reference rate model, the field stabilization effect, the 

alpha/beta H-bond effect, and the steric effect. 

The observed rates of hydrolysis of organic compounds, including the carboxylic acid 

phosphate esters, increases with temperature (see Figure 2). Figure 2 also illustrates the 

predictive power of the SPARC model versus measured values for three esters undergoing 

alkaline hydrolysis in three different solvents. 

-3 

-2.5 

-2 

-1.5 

-1 

-0.5 

0 

0 10 20 30 40 50 60 

temperature (degree Celsius) 

log Hydroylsis Rate Constant (

M-1 s -1 ) 

methyl benzoate 

cyclohexyl acetate 

cyclopropyl acetate 

Figure 2. Log hydrolysis rate constants vs temperature for alkaline hydrolysis of methyl benzoate in 80% 

methanol-water (circles), cyclopropyl acetate in pure water (triangles), and cyclohexyl acetate in 70% 

acetone (diamonds). Solid symbols are observed values, empty symbols represent calculated values. 

30
6. RESULTS AND DISCUSSIONS 

SPARC’s computational methodology is based on structure query and analysis. This 

involves combining the perturbation potentials of perturber units with the susceptibilities of the 

reaction center. The reaction parameters that describe a given reaction center are constant, 

regardless of the appended molecular structure. The same is true of substituents; the parameters 

that describe their mechanistic contributions are independent of the rest of the molecule. This 

structure factorization and mechanistic specification enables the construction of virtually any 

molecule and computation of its properties. 

Thus, in the estimation of any molecular property via SPARC, the contributions of the 

structural components C, S, and R are quantified independently. For example, the strength of a 

substituent, S, in creating an electrostatic field effect depends only on the substituent, regardless 

of the reaction center, C, the appended molecular conductor, R, or the property of interest. 

Likewise, R is modeled so as to be independent of the identities of S, C, or the property being 

estimated. Hence, S and R parameters for hydrolysis rate are the same as those for pKa or 

electron affinity. The susceptibility of a C to an electrostatic effect quantifies only the 

differential interaction of the initial state versus the final state with the electrostatic fields. The 

susceptibility gauges only the reaction Cinitial – C transition state, and is completely independent of R 

or S. Thus, no modifications in any of the previously developed pKa models in SPARC or any 

extra parameterization for either S or R, were needed to calculate the hydrolysis rate constant 

using the pKa models, other than inferring the electronegativity and the susceptibilities of 

carboxylic acid ester and phosphate ester hydrolysis rate constants to electrostatic, resonance, 

steric and solvation effects. 

31
Table 1 displays the aggregate statistical performance of the SPARC-calculated versus 

observed hydrolysis rate constants for all tests of the hydrolysis rate models to date. Figures 3-5 

present observed versus SPARC-calculated values of carboxylic acid ester hydrolysis rate 

constants undergoing base, acid and general base catalyzed hydrolysis, respectively. These 

carboxylic acid ester test sets represent 321, 416 and 50 unique esters undergoing base, acid and 

general-base catalyzed hydrolysis, respectively. Because several of the esters were measured 

under different conditions (solvents, temperatures, etc) there were 654, 667 and 150 base, acid 

and general base-catalyzed calculations performed. The RMS deviations between the SPARCcalculated and observed values for each of these reaction mechanisms were 0.37, 0.37 and 0.39 

log M-1s

-1, respectively. A sample calculation of the acid hydrolysis rate constant for pnitrophenyl acetate is shown in the appendix. 

The same chemical hydrolysis models were used to estimate base, acid and neutral 

organophosphorus hydrolysis rate constants in water as a function of temperature from molecular 

structure. Results were tested against 225 base, 83 acid and 89 neutral measured 

organophosphorus hydrolysis rate constants. The RMS deviation error between the observed and 

SPARC-calculated values were 0.40, 41 and 1.08 log M-1s

-1 for the base, acid and neutral 

hydrolysis organophosphate ester rate constants, respectively also as is reported in Table 1B. 

We discovered that to expand our model to fluorine leaving groups on organophosphate 

esters base hydrolysis, all that was required was a single addition to the reference rate model. 

This addition took the form of redefining the Ref1 constant. The remaining portions of the model 

use the parameters of the group that will hydrolyze after the fluorine-containing group. For 

example, if the compound has two additional leaving groups and one is an aromatic group and 

32
the other is aliphatic, then the aromatic parameters will be used. This resulted in a fluorinecontaining organophosphate esters hydrolysis model with a RMS of 0.268 log M-1s

-1. 

The organophosphate ester base-catalyzed hydrolysis calculator was initially trained on 

15 compounds (29 data points), chosen by visual inspection to span all hydrolysis mechanisms. 

This training set had a RMS deviation of 0.403 log M_1s

_1 and a R2

 value of 0.97. The calculator 

was then tested on 78 other compounds (196 data points) with a RMS deviation of 0.50 log 

M_1s

_1 and a R2

 value of 0.95. 

Acid catalyzed and neutral hydrolysis rate constants have been measured by many groups 

[37, 42-47]. Unfortunately, the interlab agreement between measurements of the same 

compounds is low. This experimental data varies by a much greater amount than that reported 

for base catalyzed hydrolysis. The variance is partially due to the slow hydrolysis rate of acid 

and neutral solutions as compared to alkaline hydrolysis. Slow hydrolysis rates (hundreds of 

years) require sensitive instruments to detect any change in the composition of the solution. 

Also, these compounds are usually synthesized as inorganic species or complexes and accurate 

measurements depend on being able to measure the transformation of a single species. Acid 

catalyzed hydrolysis doesn’t really begin to occur until a pH of 2 or lower is reached and for 

many compounds, it doesn’t begin until the solution is at a negative pH. Further complicating 

matters is the ionization or multiple ionization of the compound that occurs. This can lead to 

different concentrations of various species, obscuring the overall hydrolysis rate. In neutral 

hydrolysis, much of the same is true, with the pH range being from 2-8. For most components in 

this range, the hydrolysis rate is only approximately constant. This is due to competing 

mechanisms which occur at the same time. A complete listing of the compounds used to develop 

these models can be found in Tables 18 and 19. These compounds represent the best 

33
experimentally measured data available for these types of phosphate ester hydrolysis. SPARC’s 

acid catalyzed hydrolysis model is robust and accurately represents the mechanisms influencing 

the hydrolysis rate constant. In order to determine the parameters for the mechanisms that 

describe acid catalyzed hydrolysis, the model was trained on all the data found in the literature: 

28 compounds, at a variety of temperatures (83 data points). The neutral model is not as 

accurate as most SPARC models, however, as the disparity of measurements as reported in the 

literature preclude a more accurate model. The same procedure was repeated for neutral 

hydrolysis model as for acid: 36 compounds (89 data points) were found in the literature and 

used to train the parameters. 

-6 

-2 

2 

6 

10 

-6 -2 2 6 Ob se r v ed 

SPARC-Calculated 

Figure 3. SPARC-calculated vs. observed log hydrolysis rate constants for alkaline hydrolysis of 

carboxylic acid esters in six different solvents. The RMS deviation error of the log values is 

0.37 M-1s

-1 and R2 is 0.97. See Tables 2-7. 

34
-1 0 

-8 

-6 

-4 

-2 

0 

-1 0 -8 -6 -4 -2 0 

O b ser ved 

SPARC-Calculated 

Figure 4. SPARC-calculated vs. observed log hydrolysis rate constants for acid hydrolysis of carboxylic 

acid esters in five solvents and at different temperatures. The RMS deviation error of the log values is 

0.37 M-1s

-1and R2 is 0.97. See Tables 8-12. 

- 1 2 

-7 

-2 

3 

- 1 2 - 7 -2 3 

Ob se rv e d 

SPA

R

C-C

alc

ulated 

Figure 5. SPARC-calculated vs. observed log hydrolysis rate constants for general alkaline base 

hydrolysis of carboxylic acid esters in four different solvents and at different temperatures. The RMS 

deviation error of the log values is 0.39 M-1s

-1and R2 is 0.97. See Tables 13-16. 

35
Table1A. Statistical comparison of SPARC-calculated to observeda values of log hydrolysis rate 

constants of carboxylic acid ester in water and in mixed solvent systems 

Training Set Test Sets 

All Mechanisms 

(Base, Acid, 

Neutral) 

Solvent Total. 

Comp 

Base 

Catalyzed 

Acid 

Catalyzed 

Neutral 

Catalyzed 

No RMS R2 No RMS R2 No RMS R2 No RMS R2 

705 0.33 0.98 Water 576 142 0.39 0.98 383 0.36 0.98 51 0.34 0.98 

Acetone 

/Water 

424 143 0.34 0.83 208 0.33 0.96 73 0.36 0.96 

Ethanol 

/Water 

153 105 0.29 0.83 39 0.17 0.98 9 0.1 0.99 

Methanol 

/Water 

172 150 0.36 0.78 22 0.22 0 .95 N/A N/A N/A 

Dioxnae/ 

Water 

122 90 0.47 0.75 15 0.16 0.87 17 0.47 0.67 

Aceteonitrile 

/Water 

24 24 0.3 0.97 N/A N/A N/A N/A N/A N/A 

Total 1471 654 0.37 0.96 667 0.37 0.97 150 0.39 0.97 

a: Observed values are from many sources, see Tables 2-16. Units are (L/mole) s

-1 

Table1B. Statistical comparison of SPARC-calculated to observeda values of log hydrolysis 

rate constants of organophosphorus in water 

Training Set Test Sets 

All Mechanisms 

(Base, Acid, Neutral) 

Total. 

Comp 

Base-Catalyzed Acid-Catalyzed Neutral -Catalyzed 

No RMS R2 

397 

No RMS R2 No RMS R2 No RMS R2 

278b 0.38 0.94 225 0.40 0.93 83 0.41 0.81 89 1.08 0.51 

a: Observed values are from many sources, see Tables 17-19. Units are (L/mole) s

-1 

b: The training set include all acid, neutral and 197 base hydrolysis data points 

36 
7. MODELS VERIFICATION AND VALIDATION 

In chemistry, as with all physical sciences, one can never determine the “validity” of 

any predictive model with absolute certainty. This is a direct consequence of the empirical 

nature of science. Because SPARC is expected to predict reaction parameters for processes 

for which little data exists, “validity” must drive the efficiency of the model constructs in 

“capturing” or reflecting the existing knowledge base of chemical reactivity. In every 

aspect of SPARC development, from choosing the programming environment to building 

model algorithms or rule bases, system validation and verification were important criteria. 

The basic mechanistic models in SPARC were designed and parameterized to be portable to 

any type of chemistry or organic chemical structure. This extrapolatability impacts system 

validation and verification in several ways. First, as the diversity of structures and the 

chemistry that is addressable increases, so does the opportunity for error. More importantly, 

however, in verifying against the theoretical knowledge of reactivity, specific situations can 

be chosen that offer specific challenges. This is important when verifying or validating 

performance in areas where existing data are limited or where additional data collection may 

be required. Finally, this expanded prediction capability allows one to choose, for 

exhaustive validating, the reaction parameters for which large and reliable data sets do exist 

to validate against. 

In SPARC, the experimental data for physicochemical properties (such as hydrolysis 

rate constant, or ionization pKa) are not used to develop (or directly impact) the model that 

calculates that particular property. Instead, physicochemical properties are predicted using a 

few models that quantify the underlying phenomena that drive all types of chemical 

behavior (e.g., resonance, electrostatic, induction, dispersion, H-bonding interactions, etc.). 

37
These mechanistic models were parameterized using a very limited set of experimental data, 

but not data for the end-use properties that will subsequently be predicted. After 

verification, the mechanistic models were used in (or ported to) the various software 

modules that calculate the various end-use properties (such as chemical reduction or 

hydrolysis rate constant). It is critical to recognize that the same mechanistic model (e.g., 

H-bonding model) will appear in all of the software modules that predict the various end-use 

properties (e.g., chemical hydrolysis rate constant or ionization pKa) for which that 

phenomenon is important. Thus, any comparison of SPARC-calculated physicochemical 

properties to an adequate experimental data set is a true model validation test -- there is no 

training (or calibration) data set in the traditional sense for that particular property. The 

SPARC physical properties and chemical reactivity parameters models have been tested and 

validated on more than 10,000 data points [48]. 

A quality assurance (QA) plan was developed to recalculate all the hydrolysis rate 

constants reported in Tables 2-19 and compare each calculation to an originally-calculated-value 

stored in the SPARC databases. Under this plan, every quarter, two batch files that contain all the 

hydrolysis rate constants data recalculate various hydrolysis rate constants. The QA software 

compares every single “new” output to the SPARC originally-calculated-value in earlier date 

(stored in SPARC database). In this way, we ensure that existing parameter models still work 

correctly after new capabilities and improvements are added to SPARC. This also ensures that 

the computer code for hydrolysis rate constants and other mechanistic models are fully 

operational. 

38
8. TRAINING AND MODEL PARAMETER INPUT 

All quantitative chemical models require, at some point, calibration or parameterization. 

The quality of computational output necessarily reflects the quality of the calibration parameters. 

For this reason, a self-training complement (TRAIN) to SPARC was developed. Although a 

detailed description of TRAIN will not be given at this time, the following is a general review. 

For a given set of targeted model parameters, the program takes initial “guesstimates” (and the 

appropriate boundary constraints) together with a set of designated training data and provides an 

optimized set of model parameters. TRAIN cycles once or iteratively through Jacobian 

optimization procedure that is basically a non-linear, least square matrix method. TRAIN setsup and executes the optimization specifics according to user prescription. 

39
-1 

Table 2. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate 

constants for carboxylic acid esters in water as a function of temperature in M-1s 

Num Esters Obs Calc Temp Ref 

1 Methyl formate 1.4 1.1 25 [49] 

2 Ethyl formate 1.4 1.1 25 [49] 

3 Propyl formate 1.2 1.1 25 [49] 

4 Butyl formate 1.3 1.1 25 [49] 

5 Methyl dichloroacetate 3.2 3.1 25 [49] 

6 Ethyl difluoroacetate 3.7 3.8 25 [49] 

7 Ethyl methyl sulfoxide acetate 0.6 0.5 25 [49] 

8 Ethyl methyl sulfone acetate 1.1 2.2 25 [49] 

9 Methyl acetate -0.7 -0.4 25 [50] 

10 Ethyl acetate -1 -0.6 25 [51] 

11 Propyl acetate -1.1 -0.7 25 [51] 

12 Butyl acetate -1.1 -0.7 25 [51] 

13 Isopropyl acetate -1.5 -0.9 25 [51] 

14 Cyclopropyl acetate -0.6 -0.5 25 [51] 

15 Cyclopentyl acetate -1.4 -0.9 25 [51] 

16 b-Methoxyethyl acetate -0.7 -0.4 25 [51] 

17 b-Chloroethyl acetate -0.4 -0.2 25 [51] 

18 Chloromethyl acetate 1.8 1.8 25 [51] 

19 Dichloromethyl acetate 3.2 3.4 25 [51] 

20 Trichloromethyl acetate 4.1 3.9 25 [51] 

21 Bromomethyl acetae 2 1.7 25 [51] 

22 Dimethyl-amino-ethyl acetate -1 -0.4 25 [51] 

23 Ethyl propionate -1 -1 25 [51] 

24 Ethyl butyrate -1.3 -1.2 25 [51] 

25 Ethyl sec-butyrate -1.5 -1.4 25 [51] 

26 Ethyl neopentate -2.8 -2 25 [51] 

27 Ethyl fluoroacetate 1.1 1.9 25 [51] 

28 Ethyl chloroacetate 1.5 1.5 25 [51] 

29 Methyl chloroacetate 1.8 1.6 25 [51] 

30 Ethyl dichloroacetate 2.8 3 25 [51] 

31 Ethyl trichloroacetate 3.4 3.5 25 [51] 

32 Isopropyl trichloroacetate 2.6 3.2 25 [51] 

33 Ethyl bromoacetate 1.7 1.3 25 [51] 

34 Methyl bromoacetate 2 1.5 25 [51] 

35 Ethyl dibromoacetate 2.3 2.4 25 [51] 

36 Ethyl bromopropionate 1 0.8 25 [51] 

37 Ethyl iodoacetate 1.2 1.1 25 [51] 

38 Ethyl methoxyacetate 0.1 0.2 25 [51] 

39 Ethyl oxyacetate 0 -0.1 25 [51] 

40 Ethyl methyl thioacetate 0 0.2 25 [51] 

40
Num Esters Obs Calc Temp Ref 

41 Ethyl aminoacetate -0.2 -0.3 25 [51] 

42 Acetic acid, 1-Pentene, 3-methyl- ester -2.4 -1.1 25 [51] 

43 Vinyl acetate 0.6 1 25 [51] 

44 Ethyl acrylate -1.1 -0.7 25 [51] 

45 2-Butenoic acid, ethyl ester -1.9 -2.1 25 [51] 

46 Ethyl 2-butynoate -0.3 -1.2 25 [51] 

47 Ethyl propiolate 0.7 0.6 25 [51] 

48 p-Nitrophenyl chloroacetate 3.8 3.2 25 [51] 

49 Phenyl dichloroacetate 4.1 4 25 [51] 

50 Ethyl benzoate -1.5 -1.3 25 [51] 

51 Ethyl p-aminobenzoate -2.6 -2.8 25 [51] 

52 Ethyl p-nitrobenzoate -0.1 -0.3 25 [51] 

53 Ethyl p-fluorobenzoate -1.4 -1.3 25 [51] 

54 Ethyl m-aminobenzoate -1.6 -1.8 25 [51] 

55 Methyl benzoate -1.1 -1.1 25 [51] 

56 Isopropyl benzoate -2.2 -1.5 25 [51] 

57 p-Tolyl benzoate -0.5 -0.3 25 [51] 

58 m-cyanophenyl benzoate 0.3 0.4 25 [51] 

59 p-Nitrophenyl benzoate 0.4 0.5 25 [51] 

60 2,4-dinitrophenyl benzoate 1.2 1.7 25 [51] 

61 Phenyl acetate -0.3 0.5 25 [51] 

62 Phenyl propionate 0.1 0 25 [51] 

63 Phenyl butyrate -0.1 -0.1 25 [51] 

64 Phenyl sec-butyrate -0.2 -0.4 25 [51] 

65 Phenyl pentate -0.2 -0.2 25 [51] 

66 Phenyl sec-pentate -0.6 -0.9 25 [51] 

67 Phenyl neopentate -0.9 -1 25 [51] 

68 Phenyl (t-butyl)acetate -0.3 -0.9 25 [51] 

69 p-Methoxyphenyl acetate 0 0.2 25 [51] 

70 p-Methoxyphenyl propionate -0.1 -0.2 25 [51] 

71 p-Methoxyphenyl butyrate -0.1 -0.4 25 [51] 

72 p-Methoxyphenyl sec-butyrate -0.3 -0.6 25 [51] 

73 p-Methoxyphenyl pentate -0.2 -0.4 25 [51] 

74 p-Methoxyphenyl sec-pentate -0.6 -1.1 25 [51] 

75 p-Methoxyphenyl neopentate -0.9 -1.2 25 [51] 

76 o-Nitrophenyl acetate 1.3 1.1 25 [50] 

77 p-Nitrophenyl acetate 1.5 1.2 25 [50] 

78 p-Nitrophenyl propionate 0.9 0.7 25 [50] 

79 p-Nitrophenyl butyrate 0.8 0.5 25 [50] 

80 p-Nitrophenyl sec-butyrate 0.7 0.3 25 [50] 

81 p-Nitrophenyl pentate 0.7 0.5 25 [50] 

82 p-Nitrophenyl sec-pentate 0.5 -0.2 25 [50] 

41
Nu

m Esters Obs Calc Temp Ref 

83 p-Nitrophenyl neopentate 0.1 -0.3 25 [50] 

84 o-Fluorophenyl acetate 0.9 0.9 25 [50] 

85 o-Chlorophenyl acetate 0.7 1 25 [50] 

86 o-Bromophenyl acetate 0.8 0.9 25 [50] 

87 o-Iodophenyl acetate 0.7 0.9 25 [50] 

88 o-Methylphenyl acetate 0.1 0 25 [50] 

89 o-Ethylphenyl acetate 0.1 -0.2 25 [50] 

90 o-Isopropylphenyl acetate 0 -0.5 25 [50] 

91 o-(t-Butyl)phenyl acetate -0.3 -0.8 25 [50] 

92 o-Methoxyphenyl acetate 0.3 0.3 25 [50] 

93 o-Nitrophenyl acetate 1.3 1.6 25 [50] 

94 o-Cyanophenyl acetate 1.5 1.6 25 [50] 

95 m-Fluorophenyl acetate 0.9 0.7 25 [50] 

96 m-Bromophenyl acetate 0.9 0.8 25 [50] 

97 m-Methylphenyl acetate 0.4 0.4 25 [50] 

98 m-Ethylphenyl acetate 0.4 0.4 25 [50] 

99 m-Methoxyphenyl acetate 0.6 0.5 25 [50] 

100 m-Nitrophenyl acetate 1 1.1 25 [50] 

101 m-Cyanophenyl acetate 1.2 1 25 [50] 

102 p-Fluorophenyl acetate 0.6 0.6 25 [50] 

103 p-Chlorophenyl acetate 0.8 0.6 25 [50] 

104 p-Bromophenyl acetate 0.7 0.6 25 [50] 

105 p-Ethylphenyl acetate 0.3 0.3 25 [50] 

106 p-(t-Butyl)phenyl acetate 0.3 0.3 25 [50] 

107 p-Cyanophenyl acetate 1.3 1.1 25 [50] 

108 (p-Ethanal)phenyl acetate 1 0.7 25 [50] 

109 Isopropyl acetate -0.8 -0.6 20 [52] 

110 Cyclopropyl acetate -0.1 -0.2 40 [52] 

111 Vinylic acetate -0.2 0.5 0.2 [52] 

112 Vinylic acetate 0.5 0.9 20 [52] 

113 Isopropenyl acetate -1.2 0.3 0.2 [52] 

114 Isopropenyl acetate -0.5 0.6 20 [52] 

115 Cyclopentenyl acetate -0.1 0 0.2 [52] 

116 Cyclopentenyl acetate 0.4 0.3 20 [52] 

117 Cyclohexyl acetate -0.8 -1.2 20 [52] 

118 Cyclohexyl acetate -0.3 -0.8 40 [52] 

119 Cyclopentyl acetate -1.6 -1.1 20 [52] 

120 Cyclopentyl acetate -1 -0.7 40 [52] 

121 Butyl acetate -1.2 -0.8 20 [52] 

122 Ethyl chloroacetate 1.3 1.4 15 [53] 

123 Ethyl chloroacetate 1.7 1.6 35 [53] 

124 Ethyl dichloroacetate 2.7 2.9 15 [53] 

42
Num Esters Obs Calc Temp Ref 

125 Ethyl dichloroacetate 3 3 35 [53] 

126 Ethyl trichloroacetate 3.3 3.5 15 [53] 

127 Ethyl trichloroacetate 3.5 3.5 35 [53] 

128 Ethyl bromoacetate 1.5 1.2 15 [53] 

129 Ethyl bromoacetate 1.8 1.4 35 [53] 

130 Ethyl iodoacetate 1.1 1 15 [53] 

131 Ethyl iodoacetate 1.4 1.2 35 [53] 

132 Ethyl dibromoacetate 2.5 2.4 35 [53] 

133 Methyl chloroacetate 1.5 1.5 15 [53] 

134 Methyl chloroacetate 2 1.8 35 [53] 

135 Mehtyl bromoacetate 1.8 1.3 15 [53] 

136 Mehtyl bromoacetate 2.2 1.6 35 [53] 

137 Methyl dichloroacetate 3 3.1 15 [53] 

138 Methyl dichloroacetate 3.3 3.2 35 [53] 

139 Ethyl trifluoroacetate 5.2 4.7 15 [53] 

140 Isopropyl trichloroacetate 2.7 3.3 35 [53] 

141 Chloromethyl acetate 0.8 1.7 15 [53] 

142 Ethyl 2-pyridine-carboxylate -0.3 0.3 25 [49] 

43
-1 

 Table 3. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate constants 

 for carboxylic acid esters in water-acetone mixture as a function of temperature in M-1s 

Num Esters Obs. Calc. Temp Solvent. Ref. 

1 Methyl formate 1.2 0.8 25 37% Acetone [54] 

2 Ethyl formate 1 0.8 25 37% Acetone [54] 

3 Propyl formate 0.9 0.8 25 37% Acetone [54] 

4 Isopropyl formate 0.5 0.8 25 37% Acetone [54] 

5 Butyl formate 0.8 0.8 25 37% Acetone [54] 

6 sec-Butyl formate 0.3 0.8 25 37% Acetone [54] 

7 Isobutyl formate 0.8 0.8 25 37% Acetone [54] 

8 Pentyl formate 0.7 0.8 25 37% Acetone [54] 

9 Isopentyl formate 0.7 0.8 25 37% Acetone [54] 

10 Methyl acetate -0.8 -0.8 25 37% Acetone [54] 

11 Methyl propionate -1 -1.3 25 37% Acetone [54] 

12 Methyl butyrate -1.3 -1.5 25 37% Acetone [54] 

13 Methyl isobutyrate -1.4 -1.5 25 37% Acetone [54] 

14 Ethyl acetate -1.2 -1 25 37% Acetone [54] 

15 propyl acetate -1.3 -1 25 37% Acetone [54] 

16 Butyl acetate -1.4 -1.1 25 37% Acetone [54] 

17 sec-Butyl acetate -2.2 -1.9 25 37% Acetone [54] 

18 Isobutyl acetate -1.5 -1.1 25 37% Acetone [54] 

19 Pentyl acetate -1.5 -1.1 25 37% Acetone [54] 

20 Isopentyl acetate -1.5 -1.6 25 37% Acetone [54] 

21 Hexyl acetate -1.5 -1.1 25 37% Acetone [54] 

22 Ethyl propionate -1.3 -1.5 25 37% Acetone [54] 

23 Ethyl butyrate -1.7 -1.7 25 37% Acetone [54] 

24 Methyl acetate -1 -1.1 25 70% Acetone [55] 

25 Ethyl acetate -1.3 -1.3 25 70% Acetone [55] 

26 propyl acetate -1.6 -1.4 25 70% Acetone [55] 

27 Isopropyl acetate -2.2 -1.8 25 70% Acetone [55] 

28 sec-Butyl acetate -1.7 -1.5 25 70% Acetone [55] 

29 Butyl acetate -1.6 -1.5 25 70% Acetone [55] 

30 sec-Butyl acetate -2.5 -2.6 25 70% Acetone [55] 

31 t-Butyl acetate -3.6 -2.7 25 70% Acetone [55] 

32 Cyclohexyl acetate -2.3 -2.1 25 70% Acetone [55] 

33 Methyl propionate -1.2 -1.7 25 70% Acetone [55] 

34 Ethyl propionate -1.7 -2 25 70% Acetone [55] 

35 Isopropyl propionate -2.5 -2.4 25 70% Acetone [55] 

36 Butyl propionate -2 -2.1 25 70% Acetone [55] 

37 Benzyl benzoate -2.2 -1.9 25 70% Acetone [55] 

38 p-Methylbenzyl benzoate -2.3 -2 25 70% Acetone [55] 

39 m-Methylbenzyl benzoate -2.2 -2 25 70% Acetone [55] 

44
Num Esters Obs. Calc. Temp Solvent Ref. 

40 p-Ethylbenzyl benzoate -2.3 -2 25 70% Acetone [55] 

41 p-Isopropylbenzyl benzoate -2.3 -2 25 70% Acetone [55] 

42 p-(t-Butyl)benzyl benzoate -2.3 -2 25 70% Acetone [55] 

43 p-Methoxylbenzyl benzoate -2.3 -2.1 25 70% Acetone [55] 

44 p-Phenoxybenzyl benzoate -2.1 -1.9 25 70% Acetone [55] 

45 (p-Methiol)benzyl benzoate -2.1 -1.9 25 70% Acetone [55] 

46 (m-Methiol)benzyl benzoate -2 -1.8 25 70% Acetone [55] 

47 p-Phenylbenzyl benzoate -2.1 -1.8 25 70% Acetone [55] 

48 2-Naphthylcarbinyl benzoate -2.1 -1.8 25 70% Acetone [55] 

49 p-Fluorobenzyl benzoate -2 -1.8 25 70% Acetone [55] 

50 p-Chlorobenzyl benzoate -1.9 -1.7 25 70% Acetone [55] 

51 m-Chlorobenzyl benzoate -1.8 -1.6 25 70% Acetone [55] 

52 p-Bromobenzyl benzoate -1.9 -1.7 25 70% Acetone [55] 

53 m-Bromobenzyl benzoate -1.8 -1.6 25 70% Acetone [55] 

54 p-Nitrobenzyl benzoate -1.4 -1.2 25 70% Acetone [55] 

55 m-Nitrobenzyl benzoate -1.5 -1.3 25 70% Acetone [55] 

56 p-Cyanobenzyl benzoate -1.5 -1.2 25 70% Acetone [55] 

57 m-Cyanobenzyl benzoate -1.5 -1.3 25 70% Acetone [55] 

58 p-methylsulfoxide benzyl benzoate -1.6 -1.4 25 70% Acetone [55] 

59 p-methylsulfone benzyl benzoate -1.4 -1.3 25 70% Acetone [55] 

60 m-methylsulfone benzyl benzoate -1.5 -1.3 25 70% Acetone [55] 

61 2-Fluorenylcarbinyl benzoate -2.2 -1 25 70% Acetone [55] 

62 1-Naphthylcarbinyl benzoate -2.1 -1.9 25 70% Acetone [55] 

63 2-Phenanthrylcabinyl benzoate -2 -1.8 25 70% Acetone [55] 

64 3-Phenanthrylcarbinyl benzoate -2.1 -1.7 25 70% Acetone [55] 

65 9-Phenanthrylcarbinyl benzoate -2 -1.9 25 70% Acetone [55] 

66 9-Anthrylcarbinyl benzoate -2.2 -1.7 25 70% Acetone [55] 

67 Ethyl phenylacetate -1.4 -1.4 25 60% Acetone [56] 

68 Ethyl o-fluorophenylacetate -1.5 -1.8 25 60% Acetone [56] 

69 Ethyl o-chlorophenylacetate -1.8 -1.9 25 60% Acetone [56] 

70 Ethyl o-bromophenylacetate -1.9 -2 25 60% Acetone [56] 

71 Ethyl o-iodophenylacetate -1.9 -2.1 25 60% Acetone [56] 

72 Ethyl m-iodophenylacetate -1.1 -1.3 25 60% Acetone [56] 

73 Ethyl o-methylphenylacetate -2 -2.1 25 60% Acetone [56] 

74 Ethyl o-butylphenylacetate -2.8 -2.5 25 60% Acetone [56] 

75 Ethyl 1,6-dichlorophenylacetate -2.9 -2.4 25 60% Acetone [56] 

76 Ethyl p-(t-butyl)phenylacetate -1.7 -1.6 25 60% Acetone [57] 

77 Ethyl p-dimethylaminophenylacetate -1.6 -1.9 25 60% Acetone [57] 

78 Ethyl o-nitrophenylacetate -1.6 -2 25 60% Acetone [57] 

79 Ethyl p-aminophenylacetate -1.5 -1.9 25 60% Acetone [57] 

80 Ethyl m-methoxyphenylacetate -1.3 -1.5 25 60% Acetone [57] 

45
Num Esters Obs. Calc. Temp Solvent [57] 

81 Ethyl (3,4-biphenyl)phenylacetate -1.3 -1.4 25 60% Acetone [57] 

82 Ethyl (p-phenyl)phenylacetate -1.5 -1.4 25 60% Acetone [57] 

83 Ethyl p-iodophenylacetate -1.2 -1.3 25 60% Acetone [57] 

84 Ethyl m-chlorophenylacetate -1 -1.4 25 60% Acetone [57] 

85 Ethyl m-fluorophenylacetate -1 -1.4 25 60% Acetone [57] 

86 Ethyl p-cyanophenylacetate -0.7 -1.1 25 60% Acetone [57] 

87 Ethyl p-nitrophenylacetate -0.6 -1.1 25 60% Acetone [57] 

88 Ethyl m-nitrophenylacetate -0.8 -1.2 25 60% Acetone [57] 

89 Ethyl p-bromophenylacetate -1 -1.4 25 60% Acetone [57] 

90 Ethyl p-chlorophenylacetate -1 -1.4 25 60% Acetone [57] 

91 Ethyl p-fluorophenylacetate -1.2 -1.4 25 60% Acetone [57] 

92 Ethyl p-methoxyphenylacetate -1.4 -1.7 25 60% Acetone [57] 

93 Ethyl p-methylphenylacetate -1.6 -1.6 25 60% Acetone [57] 

94 Methyl phenylacetate -0.9 -1.5 25 75% Acetone [58] 

95 Methyl 9-anthrylacetate -1.8 -2.3 25 75% Acetone [58] 

96 Methyl 9-phenanthrylacetate -1.4 -1.7 25 75% Acetone [58] 

97 Methyl 1-naphthylacetate -1.3 -1.7 25 75% Acetone [58] 

98 Methyl p-methylbenzoate -1 -1.7 25 75% Acetone [58] 

99 Methyl 2-naphthylacetate -0.8 -1.4 25 75% Acetone [58] 

100 Methyl 4-biphenylacetate -0.8 -1.4 25 75% Acetone [58] 

101 Methyl 2-anthrylacetate -0.8 -1.4 25 75% Acetone [58] 

102 Methyl 3-phenanthrylacetate -0.8 -1.4 25 75% Acetone [58] 

103 Methyl 2-phenanthrylacetate -0.8 -1.5 25 75% Acetone [58] 

104 Methyl acetate -1 -1.2 20 70% Acetone [55] 

105 Ethyl acetate -1.5 -1.4 20 70% Acetone [55] 

106 Ethyl acetate -1.3 -1.1 35 70% Acetone [55] 

107 Ethyl acetate -0.9 -0.9 44.7 70% Acetone [55] 

108 Propyl acetate -1.7 -1.5 20 70% Acetone [55] 

109 Propyl acetate -1.3 -1.2 35 70% Acetone [55] 

110 Propyl acetate -1 -1 44.7 70% Acetone [55] 

111 Isopropyl acetate -2.3 -1.9 20 70% Acetone [55] 

112 Isopropyl acetate -1.9 -1.6 35 70% Acetone [55] 

113 Isopropyl acetate -1.6 -1.4 44.7 70% Acetone [55] 

114 Isobutyl acetate -1.9 -1.6 20 70% Acetone [55] 

115 Isobutyl acetate -1.4 -1.3 35 70% Acetone [55] 

116 Isobutyl acetate -1.2 -1.1 44.7 70% Acetone [55] 

117 n-Butyl acetate -1.8 -1.6 20 70% Acetone [55] 

118 n-Butyl acetate -1.6 -1.3 35 70% Acetone [55] 

119 n-Butyl acetate -1.1 -1.1 44.7 70% Acetone [55] 

120 sec-Butyl acetate -2.6 -2.7 20 70% Acetone [55] 

121 sec-Butyl acetate -2.2 -2.3 35 70% Acetone [55] 

122 sec-Butyl acetate -1.9 -2.2 44.7 70% Acetone [55] 

46
Num Esters Obs. Calc. Temp Solvent Ref. 

123 t-Butyl acetate -3.2 -2.5 35 70% Acetone [55] 

124 t-Butyl acetate -3 -2.3 44.7 70% Acetone [55] 

125 Cyclohexyl acetate -2 -1.9 35 70% Acetone [55] 

126 Cyclohexyl acetate -1.8 -1.7 44.7 70% Acetone [55] 

127 Methyl propionate -1.3 -1.8 20 70% Acetone [55] 

128 Methyl propionate -1 -1.5 35 70% Acetone [55] 

129 Methyl propionate -0.8 -1.3 44.7 70% Acetone [55] 

130 Ethyl propionate -1.8 -2.1 20 70% Acetone [55] 

131 Ethyl propionate -1.4 -1.8 35 70% Acetone [55] 

132 Ethyl propionate -1.2 -1.6 44.7 70% Acetone [55] 

133 Isopropyl propionate -2.7 -2.6 20 70% Acetone [55] 

134 Isopropyl propionate -2.2 -2.2 35 70% Acetone [55] 

135 Isopropyl propionate -1.9 -2 44.7 70% Acetone [55] 

136 n-Butyl propionate -2.1 -2.2 20 70% Acetone [55] 

137 n-Butyl propionate -1.7 -1.9 35 70% Acetone [55] 

138 n-Butyl propionate -1.5 -1.7 44.7 70% Acetone [55] 

139 Ethyl picolinate -0.7 -0.9 25 60% acetone [59] 

140 Ethyl isonicotinate -0.2 -1.1 25 60% acetone [59] 

141 Ethyl nicotinate -0.9 -1.2 25 60% acetone [59] 

47
Table 4. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate constants of -1 carboxylic acid esters in ethanol-water mixtures as a function of temperature in M-1s 

Num Esters Obs Calc Temp. Solvent Ref 

1 Ethyl 1-naphthoate -3.6 -3 25 85% Ethanol [60] 

2 Ethyl 3-chloro-1-napthoate -2.7 -2.7 25 85% Ethanol [60] 

3 Ethyl 3-bromo-1-naphthoate -2.7 -2.7 25 85% Ethanol [60] 

4 Ethyl 4-bromo-1-naphthoate -3 -2.9 25 85% Ethanol [60] 

5 Ethyl 5-bromo-1-naphthoate -3 -2.9 25 85% Ethanol [60] 

6 Ethyl 4'-methoxy-p-biphenyl carboxylate -3.5 -2.9 25 91% Ethanol [60] 

7 Ethyl 4'-methyl-p-biphenyl carboxylate -3.4 -2.8 25 91% Ethanol [60] 

8 Ethyl p-biphenyl carboxylate -3.3 -2.7 25 91% Ethanol [60] 

9 Ethyl 4'-chloro-p-biphenyl carboxylate -3.1 -2.7 25 91% Ethanol [60] 

10 Ethyl 4'-bromo-p-biphenyl carboxylate -3.1 -2.7 25 91% Ethanol [60] 

11 Ethyl 3'-bromo-p-biphenyl carboxylate -3 -2.7 25 91% Ethanol [60] 

12 Ethyl 4'-nitro-p-biphenyl carboxylate -2.8 -2.5 25 91% Ethanol [60] 

13 Ethyl benzoate -3 -2.5 25 75% Ethanol [60] 

14 Ethyl phenylacetate -1.9 -1.7 25 85% Ethanol [56] 

15 Ethyl o-iodophenyl acetate -2.3 -2.5 25 85% Ethanol [56] 

16 Ethyl p-iodophenylacetate -1.5 -1.6 25 85% Ethanol [56] 

17 Ethyl p-nitrophenylacetate -1 -1.3 25 85% Ethanol [56] 

18 Ethyl o-methylphenylacetate -2.4 -2.5 25 85% Ethanol [56] 

19 Ethyl p-methylphenylacetate -2 -1.8 25 85% Ethanol [56] 

20 Ethyl phenylacetate -1.8 -1.6 25 75% Ethanol [56] 

21 Ethyl o-iodophenylacetate -2.2 -2.3 25 75% Ethanol [56] 

22 Ethyl p-iodophenylacetate -1.4 -1.4 25 75% Ethanol [56] 

23 Ethyl p-nitrophenylacetate -0.9 -1.2 25 75% Ethanol [56] 

24 Ethyl o-methylphenylacetate -2.3 -2.3 25 75% Ethanol [56] 

25 Ethyl p-methylphenylacetate -1.9 -1.7 25 75% Ethanol [56] 

26 Ethyl phenylacetate -1.7 -1.4 25 65% Ethanol [56] 

27 Ethyl o-chlorophenylacetate -2.1 -1.8 25 65% Ethanol [56] 

28 Ethyl o-chlorophenylacetate -1.3 -1.3 25 65% Ethanol [56] 

29 Ethyl o-bromophenylacetate -2.1 -2 25 65% Ethanol [56] 

30 Ethyl o-iodophenylacetate -2.2 -2 25 65% Ethanol [56] 

31 Ethyl p-iodophenylacetate -1.3 -1.3 25 65% Ethanol [56] 

32 Ethyl o-nitrophenylacetate -1.9 -1.9 25 65% Ethanol [56] 

33 Ethyl m-nitrophenylacetate -0.9 -1.1 25 65% Ethanol [56] 

34 Ethyl p-nitrophenylacetate -0.8 -1 25 65% Ethanol [56] 

35 Ethyl o-methylphenylacetate -2.2 -2.1 25 65% Ethanol [56] 

36 Ethyl p-methylphenylacetate -1.8 -1.5 25 65% Ethanol [56] 

37 Ethyl p-(t-butyl)phenylacetate -1.8 -1.5 25 65% Ethanol [56] 

38 Ethyl phenylacetate -2 -1.7 25 90% Ethanol [56] 

39 Ethyl o-fluorophenylacetate -2.1 -2.2 25 90% Ethanol [56] 

40 Ethyl p-fluorophenylacetate -1.8 -1.7 25 90% Ethanol [56] 

48
Num Esters Obs. Calc. Temp Solvent. Ref. 

41 Ethyl o-chlorophenylacetate -2.3 -2.3 25 90% Ethanol [56] 

42 Ethyl m-chlorophenylacetate -1.6 -1.6 25 90% Ethanol [56] 

43 Ethyl p-chlorophenylacetate -1.6 -1.6 25 90% Ethanol [56] 

44 Ethyl o-bromophenylacetate -2.4 -2.4 25 90% Ethanol [56] 

45 Ethyl p-bromophenylacetate -1.6 -1.6 25 90% Ethanol [56] 

46 Ethyl o-iodophenylacetate -2.4 -2.5 25 90% Ethanol [56] 

47 Ethyl m-iodophenylacetate -1.6 -1.6 25 90% Ethanol [56] 

48 Ethyl p-iodophenylacetate -1.6 -1.6 25 90% Ethanol [56] 

49 Ethyl o-nitrophenylacetate -2.1 -2.4 25 90% Ethanol [56] 

50 Ethyl m-nitrophenylacetate -1.1 -1.4 25 90% Ethanol [56] 

51 Ethyl p-nitrophenylacetate -1.1 -1.3 25 90% Ethanol [56] 

52 Ethyl o-methylphenylacetate -2.5 -2.5 25 90% Ethanol [56] 

53 Ethyl p-methylphenylacetate -2.1 -1.9 25 90% Ethanol [56] 

54 Ethyl o-(t-butyl)phenylacetate -3.3 -3.4 25 90% Ethanol [56] 

55 Ethyl p-(t-butyl)phenylacetate -2.1 -1.9 25 90% Ethanol [56] 

56 Ethyl o-methoxyphenylacetate -2.8 -2.8 25 90% Ethanol [56] 

57 Ethyl m-methoxyphenylacetate -2 -1.8 25 90% Ethanol [56] 

58 Ethyl p-methoxyphenylacetate -2.1 -2 25 90% Ethanol [56] 

59 Ethyl p-nitrophenylacetate -2.3 -2.1 25 90% Ethanol [56] 

60 Ethyl 1,6-dichlorophenylacetate -3.4 -2.9 25 90% Ethanol [56] 

61 Ethyl 3,4-dimethoxyphenylacetate -2 -2.1 25 90% Ethanol [56] 

62 Ethyl 1-naphthoate -3.1 -2.8 35 85% Ethanol [60] 

63 Ethyl 1-naphthoate -2.8 -2.6 45 85% Ethanol [60] 

64 Ethyl 1-naphthoate -2.5 -2.4 55 85% Ethanol [60] 

65 Ethyl 1-naphthoate -2.1 -2.3 65 85% Ethanol [60] 

66 Ethyl 3-chloro-1-naphthoate -2.7 -2.5 35 85% Ethanol [60] 

67 Ethyl 3-chloro-1-naphthoate -2 -2.3 45 85% Ethanol [60] 

68 Ethyl 3-chloro-1-naphthoate -1.6 -2.2 55 85% Ethanol [60] 

69 Ethyl 4-chloro-1-naphthoate -2.6 -2.8 35 85% Ethanol [60] 

70 Ethyl 4-chloro-1-naphthoate -2.2 -2.6 45 85% Ethanol [60] 

71 Ethyl 4-chloro-1-naphthoate -1.9 -2.4 55 85% Ethanol [60] 

72 Ethyl 4-chloro-1-naphthoate -2.5 -2.2 65 85% Ethanol [60] 

73 Ethyl 3-bromo-1-naphthoate -2 -2.3 45 85% Ethanol [60] 

74 Ethyl 3-bromo-1-naphthoate -1.3 -2 65 85% Ethanol [60] 

75 Ethyl 4-bromo-1-naphthoate -2.6 -2.7 35 85% Ethanol [60] 

76 Ethyl 4-bromo-1-naphthoate -1.9 -2.4 55 85% Ethanol [60] 

77 Ethyl 4-bromo-1-naphthoate -1.5 -2.2 65 85% Ethanol [60] 

78 Ethyl 5-bromo-1-naphthoate -2.3 -2.5 45 85% Ethanol [60] 

79 Ethyl 5-bromo-1-naphthoate -1.9 -2.3 55 85% Ethanol [60] 

80 Ethyl 5-bromo-1-naphthoate -1.6 -2.1 65 85% Ethanol [60] 

81 Ethyl 4-methyl-1-naphthoate -3.1 -3.2 45 85% Ethanol [60] 

82 Ethyl 4-methyl-1-naphthoate -2.8 -3 55 85% Ethanol [60] 

49
Num Esters Obs. Calc. Temp Solv. Ref. 

83 Ethyl 4-methyl-1-naphthoate -2.4 -2.8 65 85% Ethanol [60] 

84 Ethyl 4-methyl-1-naphthoate -2 -2.6 75 85% Ethanol [60] 

85 Ethyl 3-methyl-1-naphthoate -2.9 -2.7 45 85% Ethanol [60] 

86 Ethyl 3-methyl-1-naphthoate -2.6 -2.5 55 85% Ethanol [60] 

87 Ethyl 3-methyl-1-naphthoate -2.2 -2.4 65 85% Ethanol [60] 

88 Ethyl 3-methyl-1-naphthoate -1.9 -2.2 75 85% Ethanol [60] 

89 Ethyl 4'-methoxy-p-biphenyl carboxylate -2.8 -2.6 40 91% Ethanol [61] 

90 Ethyl 4'-methyl-p-biphenyl carboxylate -2.7 -2.5 40 91% Ethanol [61] 

91 Ethyl p-biphenyl carboxylate -2.6 -2.4 40 91% Ethanol [61] 

92 Ethyl 4'-chloro-p-biphenyl carboxylate -2.5 -2.4 40 91% Ethanol [61] 

93 Ethyl 4'-bromo-p-biphenyl carboxylate -2.5 -2.4 40 91% Ethanol [61] 

94 Ethyl 3'-bromo-p-biphenyl carboxylate -2.4 -2.4 40 91% Ethanol [61] 

95 Ethyl 3'-nitro-p-biphenyl carboxylate -2.2 -2.3 40 91% Ethanol [61] 

96 Ethyl 4'-nitro-p-biphenyl carboxylate -2.2 -2.2 40 91% Ethanol [61] 

97 Ethyl picolinate -1.5 -1.1 17 75% Ethanol [62] 

98 Ethyl nicotinate -1.7 -1.5 17 75% Ethanol [62] 

99 Ethyl isonicotinate -0.9 -1.4 17 75% Ethanol [62] 

100 Ethyl picolinate -1.2 -1 25 75% Ethanol [62] 

101 Ethyl nicotinate -1.4 -1.3 25 75% Ethanol [62] 

102 Ethyl isonicotinate -0.7 -1.2 25 75% Ethanol [62] 

103 Ethyl picolinate -0.9 -0.8 35 75% Ethanol [62] 

104 Ethyl nicotinate -1.1 -1.1 35 75% Ethanol [62] 

105 Ethyl isonicotinate -0.4 -1 35 75% Ethanol [62] 

50
Table 5. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate constants -1 for carboxylic acid esters in methanol-water mixtures as a function of temperature in M-1s 

Num Esters Obs. Calc Temp. Solvent Ref. 

1 Methyl o-fluorobenzoate -2.6 -2.7 25 80% Methanol [63] 

2 Methyl m-nitrobenzoate -1.6 -2.2 25 80% Methanol [63] 

3 Methyl m-chlorobenzoate -2.4 -2.7 25 80% Methanol [63] 

4 Methyl benzoate -2.7 -2.2 25 60% Methanol [63] 

5 Methyl p-bromobenzoate -2.3 -2.2 25 60% Methanol [63] 

6 Methyl p-nitrobenzoate -1.1 -1.4 25 60% Methanol [63] 

7 Methyl m-bromobenzoate -2 -2 25 60% Methanol [63] 

8 Methyl m-nitrobenzoate -1.3 -1.6 25 60% Methanol [63] 

9 Methyl 9-anthrylacetate -3.3 -2.9 25 85% Methanol [58] 

10 Methyl 6-chryslacetate -2.9 -2.4 25 85% Methanol [58] 

11 Methyl 9-phenanthrylacetate -2.9 -2.4 25 85% Methanol [58] 

12 Methyl 1-naphthylacetate -2.9 -2.4 25 85% Methanol [58] 

13 Methyl 1-pyrenylacetate -2.7 -2.3 25 85% Methanol [58] 

14 Methyl p-methylphenylacetate -2.6 -2.3 25 85% Methanol [58] 

15 Methyl 2-fluorenylacetate -2.6 -1.7 25 85% Methanol [58] 

16 Methyl phenylacetate -2.5 -2.1 25 85% Methanol [58] 

17 Methyl 2-naphthylacetate -2.4 -2.1 25 85% Methanol [58] 

18 Methyl 4-biphenylacetate -2.4 -2.1 25 85% Methanol [58] 

19 Methyl 2-anthrylacetate -2.4 -2 25 85% Methanol [58] 

20 Methyl 3-phenanthrylacetate -2.4 -2.4 25 85% Methanol [58] 

21 Methyl 2-phenanthrylacetate -2.4 -2.1 25 85% Methanol [58] 

22 Methyl benzoate -2.3 -2.1 25 50% Methanol [64] 

23 Mehtyl p-nitrobenzoate -1.9 -2.3 25 88% Methanol [63] 

24 Methyl m-nitrobenzoate -2.1 -2.5 25 88% Methanol [63] 

25 Methyl m-bromobenzoate -2.9 -2.9 25 88% Methanol [63] 

26 Methyl p-bromobenzoate -3.2 -3.1 25 88% Methanol [63] 

27 Methyl m-methoxybenzoate -3.6 -3.5 25 88% Methanol [63] 

28 Methyl benzoate -3.7 -3.2 25 88% Methanol [63] 

29 Methyl m-methylbenzoate -3.9 -3.5 25 88% Methanol [63] 

30 Methyl m-dimethylaminobenzoate -4 -3.7 25 88% Methanol [63] 

31 Methyl p-methylbenzoate -4 -3.8 25 88% Methanol [63] 

32 Methyl p-methoxybenzoate -4.3 -4.3 25 88% Methanol [63] 

33 Methyl benzoate -2.8 -2.7 34.8 80% Methanol [63] 

34 Methyl benzoate -2.4 -2.5 44.8 80% Methanol [63] 

35 Methyl benzoate -2.3 -2.4 49.8 80% Methanol [63] 

36 Methyl benzoate -2 -2.3 55.2 80% Methanol [63] 

37 Methyl o-methylbenzoate -3.7 -3.5 35 80% Methanol [63] 

38 Methyl o-methylbenzoate -3.3 -3.3 45 80% Methanol [63] 

39 Methyl o-methylbenzoate -2.9 -3.1 55 80% Methanol [63] 

40 Methyl o-methylbenzoate -2.3 -2.8 70.2 80% Methanol [63] 

51
Num Esters Obs. Calc. Temp Solvent Ref. 

41 Methyl o-ethylbenzoate -3.6 -3.5 45 80% Methanol [63] 

42 Methyl o-ethylbenzoate -3.2 -3.3 55 80% Methanol [63] 

43 Methyl o-ethylbenzoate -2.5 -3 70.2 80% Methanol [63] 

44 Methyl o-ethylbenzoate -2.1 -2.9 80.4 80% Methanol [63] 

45 Methyl o-isopropylbenzoate -2.6 -3.1 71.6 80% Methanol [63] 

46 Methyl o-isopropylbenzoate -2.4 -3 78.4 80% Methanol [63] 

47 Methyl o-isopropylbenzoate -2 -2.8 89.9 80% Methanol [63] 

48 Methyl o-isopropylbenzoate -1.7 -2.6 100.2 80% Methanol [63] 

49 Methyl o-(t-butyl)benzoate -3.5 -2.4 119.8 80% Methanol [63] 

50 Methyl o-(t-butyl)benzoate -3.2 -2.2 129.8 80% Methanol [63] 

51 Methyl o-(t-butyl)benzoate -3 -2.2 134 80% Methanol [63] 

52 Methyl o-(t-butyl)benzoate -1.8 -2.1 140 80% Methanol [63] 

53 Methyl o-fluorobenzoate -3 -2.9 15.4 80% Methanol [63] 

54 Methyl o-fluorobenzoate -2.2 -2.5 35 80% Methanol [63] 

55 Methyl o-fluorobenzoate -1.8 -2.3 44.8 80% Methanol [63] 

56 Methyl o-chlorobenzoate -2.5 -2.4 35 80% Methanol [63] 

57 Methyl o-chlorobenzoate -2.2 -2.2 44.8 80% Methanol [63] 

58 Methyl o-chlorobenzoate -2 -2.1 50 80% Methanol [63] 

59 Methyl o-chlorobenzoate -1.8 -2 55 80% Methanol [63] 

60 Methyl o-bromobenzoate -2.7 -2.5 35 80% Methanol [63] 

61 Methyl o-bromobenzoate -2.3 -2.3 45 80% Methanol [63] 

62 Methyl o-bromobenzoate -2.1 -2.2 50 80% Methanol [63] 

63 Methyl o-bromobenzoate -2 -2.1 55 80% Methanol [63] 

64 Methyl o-iodobenzoate -2.9 -2.5 34.8 80% Methanol [63] 

65 Methyl o-iodobenzoate -2.5 -2.3 44.8 80% Methanol [63] 

66 Methyl o-iodobenzoate -2.3 -2.2 49 80% Methanol [63] 

67 Methyl o-iodobenzoate -2.1 -2.1 54.9 80% Methanol [63] 

68 Methyl m-nitrobenzoate -2.6 -2.6 4.6 80% Methanol [63] 

69 Methyl m-nitrobenzoate -2.1 -2.4 15 80% Methanol [63] 

70 Methyl m-nitrobenzoate -1.3 -2 34.5 80% Methanol [63] 

71 Methyl m-chlorobenzoate -2.9 -2.9 15 80% Methanol [63] 

72 Methyl m-chlorobenzoate -2 -2.5 34.5 80% Methanol [63] 

73 Methyl m-chlorobenzoate -1.6 -2.3 45.2 80% Methanol [63] 

74 Methyl m-methylbenzoate -3.1 -3.1 30.1 80% Methanol [63] 

75 Methyl m-methylbenzoate -2.7 -2.8 40.7 80% Methanol [63] 

76 Methyl m-methylbenzoate -2.3 -2.6 50 80% Methanol [63] 

77 Methyl m-methylbenzoate -2 -2.4 59.8 80% Methanol [63] 

78 Methyl 9-anthrylacetate -2.9 -2.8 32.5 85% Methanol [58] 

79 Methyl 9-phenanthrylacetate -2.6 -2.2 32.5 85% Methanol [58] 

80 Methyl 1-naphthylacetate -2.6 -2.2 32.5 85% Methanol [58] 

81 Methyl 6-chrysylacetate -2.4 -2.2 32.5 85% Methanol [58] 

82 Methyl p-methylphenylacetate -2.3 -2.2 32.5 85% Methanol [58] 

52
Num Esters Obs. Calc. Temp Solvent Ref. 

83 2-Fluorenyl phenylacetate -2.2 -1.6 32.5 85% Methanol [58] 

84 Methyl phenylacetate -2.2 -2 32.5 85% Methanol [58] 

85 Methyl 2-naphthylacetate -2.1 -1.9 32.5 85% Methanol [58] 

86 Methyl p-biphenylacetate -2.1 -1.9 32.5 85% Methanol [58] 

87 Methyl 3-phenanthrylacetate -2 -1.9 32.5 85% Methanol [58] 

88 Methyl 2-phenanthrylacetate -2.1 -1.9 32.5 85% Methanol [58] 

89 Methyl phenylacetate -2 -1.9 40 85% Methanol [58] 

90 Methyl 2-naphthylacetate -1.9 -1.8 40 85% Methanol [58] 

91 Methyl p-biphenylacetate -1.9 -1.8 40 85% Methanol [58] 

92 Methyl 2-phenanthrylacetate -1.8 -1.8 40 85% Methanol [58] 

93 Methyl 9-anthrylacetate -2.3 -2.4 50 85% Methanol [58] 

94 Methyl 9-phenanthrylacetate -2 -1.9 50 85% Methanol [58] 

95 Methyl 1-naphthylacetate -2 -1.9 50 85% Methanol [58] 

96 Methyl 6-chrysylacetate -1.8 -1.9 50 85% Methanol [58] 

97 Methyl p-methylphenylacetate -1.7 -1.8 50 85% Methanol [58] 

98 2-Fluorenyl phenylacetate -1.6 -1.3 50 85% Methanol [58] 

99 Methyl phenylacetate -1.6 -1.7 50 85% Methanol [58] 

100 Methyl 2-naphthylacetate -1.5 -1.6 50 85% Methanol [58] 

101 Methyl p-biphenylacetate -1.5 -1.6 50 85% Methanol [58] 

102 Methyl 3-phenanthrylacetate -1.5 -1.6 50 85% Methanol [58] 

103 Methyl 2-phenanthrylacetate -1.5 -1.6 50 85% Methanol [58] 

104 Methyl 9-anthrylacetate -1.9 -2.2 60.2 85% Methanol [58] 

105 Methyl 9-phenanthrylacetate -1.6 -1.7 60.2 85% Methanol [58] 

106 Methyl 2-naphthylacetate -1.6 -1.7 60.2 85% Methanol [58] 

107 Methyl 6-chrysylacetate -1.4 -1.7 60.2 85% Methanol [58] 

108 Methyl p-methylphenylacetate -1.4 -1.6 60.2 85% Methanol [58] 

109 2-Fluorenyl phenylacetate -1.3 -1.2 60.2 85% Methanol [58] 

110 Methyl 3-phenanthrylacetate -1.1 -1.4 60.2 85% Methanol [58] 

111 2-Carbomethoxyquinoline -0.5 -0.6 25 50% Methanol [64] 

112 Methyl 2-nitropicolinate -0.6 -1 25 88% Methanol [65] 

113 Methyl 2-bromopicolinate -1.5 -1.5 25 88% Methanol [65] 

114 Methyl 2-methylpicolinates -2.3 -2 25 88% Methanol [65] 

115 Methyl 2-dimethylnitropicolinate -2.9 -2.3 25 88% Methanol [65] 

116 Methyl nicotinate -1.4 -1.2 25 88% Methanol [49] 

117 Methyl picolinate -1.2 -0.9 25 88% Methanol [49] 

118 Methyl isonicotinate -0.7 -1.1 25 88% Methanol [49] 

119 Methyl 5-nitropicolinate -0.4 -0.8 25 88% Methanol [65] 

120 Methyl 5-bromopicolinate -1.5 -1.7 25 88% Methanol [65] 

121 Methyl picolinate -2 -1.8 25 88% Methanol [65] 

122 Methyl 5-methylpicolinate -2.4 -2.3 25 88% Methanol [65] 

123 Methyl 5-methoxylpicolinate -2.8 -2.8 25 88% Methanol [65] 

124 Methyl 5-dimethylnitropicolinate -3.7 -3.3 25 88% Methanol [65] 

53
Num Esters Obs. Calc. Temp Solvent Ref. 

125 Methyl 4-nitropicolinate -0.7 -1 25 88% Methanol [65] 

126 Methyl 4-bromopicolinate -1.3 -1.5 25 88% Methanol [65] 

127 Methyl 4-methylpicolinate -2.2 -2 25 88% Methanol [65] 

128 Methyl 4-methoxylpicolinate -2 -2.1 25 88% Methanol [65] 

129 Methyl 5-bromonicotinate -1.5 -1.8 25 88% Methanol [65] 

130 Methyl nicotinate -2.3 -2.1 25 88% Methanol [65] 

131 Methyl 5-methylnicotinate -2.3 -2.3 25 88% Methanol [65] 

132 Methyl 5-methoxynicotinate -2.1 -2.4 25 88% Methanol [65] 

133 Methyl 5-dimethylnitronicotinate -2.7 -2.6 25 88% Methanol [65] 

134 Methyl 2-bromonicotinate -1.8 -2 25 88% Methanol [65] 

135 Methyl 2-methylnicotinate -2.6 -2.7 25 88% Methanol [65] 

136 Methyl 2-methoxynicotinate -3.2 -3.2 25 88% Methanol [65] 

137 Methyl 2-dimethylnitronicotinate -4.3 -3.8 25 88% Methanol [65] 

138 Methyl 2-nitroisonicotinate 0.2 -1.2 25 88% Methanol [65] 

139 Methyl 2-bromoisonicotinate -0.9 -1.7 25 88% Methanol [65] 

140 Methyl isonicotinate -1.5 -2 25 88% Methanol [65] 

141 Methyl 2-methylisonicotinate -1.7 -2.2 25 88% Methanol [65] 

142 Methyl 2-methoxyisonicotinate -1.8 -2.2 25 88% Methanol [65] 

143 Methyl 2-dimethylnitroisonicotinate -2.3 -2.5 25 88% Methanol [65] 

144 3-Carbomethoxyquinoline -1.1 -0.9 25 50% Methanol [64] 

145 4-Carbomethoxyquinoline -0.8 -1.1 25 50% Methanol [64] 

146 5-Carbomethoxyquinoline -1.7 -1.4 25 50% Methanol [64] 

147 6-Carbomethoxyquinoline -1.6 -1.2 25 50% Methanol [64] 

148 7-Carbomethoxyquinoline -1.5 -1.2 25 50% Methanol [64] 

149 8-Carbomethoxyquinoline -2.4 -1.4 25 50% Methanol [64] 

54
-1 

 Table 6. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate constants 

 for carboxylic acid esters in dioxane-water mixtures as a function of temperature in M-1s 

Num Esters Obs Calc Temp. Solvent Ref. 

1 Ethyl benzoate -2.1 -1.6 30 33% dioxane [49] 

2 p-Nitrobenzyl benzoate -1.5 -1.2 25 67% dioxane [66] 

3 p-Chlorobenzyl benzoate -2 -1.4 25 67% dioxane [67] 

4 p-Chlorobenzyl benzoate -1.7 -1 25 67% dioxane [67] 

5 Benzyl benzoate -2.3 -1.5 25 67% dioxane [67] 

6 p-Methoxybenzyl benzoate -2.4 -1.5 25 67% dioxane [67] 

7 Methyl benzoate -1.6 -1.5 25 33% dioxane [67] 

8 Methyl p-aminobenzoate -2.9 -3 25 33% dioxane [67] 

9 Methyl p-methylbenzoate -2 -2 25 33% dioxane [67] 

10 Methyl p-chlorobenzoate -1.2 -1.4 25 33% dioxane [67] 

11 Methyl p-nitrobenzoate -0.2 -0.5 25 33% dioxane [67] 

12 Methyl acetate -0.5 -0.3 35 40% dioxane [68] 

13 Methyl propionate -0.6 -0.9 35 40% dioxane [68] 

14 Methyl isobutyrate -1.1 -1.1 35 40% dioxane [68] 

15 Methyl n-butyrate -0.9 -1.1 35 40% dioxane [68] 

16 Mehtyl n-pentate -1 -1.2 35 40% dioxane [68] 

17 Methyl isopentate -1.5 -1.2 35 40% dioxane [68] 

18 Methyl sec-pentate -1.6 -2.1 35 40% dioxane [68] 

19 Methyl neopentate -2 -1.4 35 40% dioxane [68] 

20 Methyl phenylacetate -0.4 -0.4 35 40% dioxane [68] 

21 Methyl benzoate -1.5 -1.7 35 60% dioxane [69] 

22 Methyl p-methylbenzoate -1.9 -2.2 35 60% dioxane [69] 

23 Methyl m-methylbenzoate -1.8 -1.9 35 60% dioxane [69] 

24 Methyl p-methoxybenzoate -2.2 -2.7 35 60% dioxane [69] 

25 Methyl p-aminobenzoate -3 -3.2 35 60% dioxane [69] 

26 Methyl p-bromobenzoate -1 -1.6 35 60% dioxane [69] 

27 Methyl m-iodobenzoate -0.9 -1.3 35 60% dioxane [69] 

28 Methyl m-chlorobenzoate -0.8 -1.4 35 60% dioxane [69] 

29 Methyl m-bromobenzoate -0.8 -1.4 35 60% dioxane [69] 

30 Methyl m-nitrobenzoate 0 -0.9 35 60% dioxane [69] 

31 Methyl p-nitrobenzoate 0.2 -0.7 35 60% dioxane [69] 

32 Ethyl benzoate -2 -1.9 35 60% dioxane [69] 

33 Propyl benzoate -2.2 -2 35 60% dioxane [69] 

34 Propyl p-chlorobenzoate -1.6 -2 35 60% dioxane [69] 

35 Isopropyl benzoate -2.8 -2.4 35 60% dioxane [69] 

36 Isopropyl p-methoxybenzoate -3.4 -3.4 35 60% dioxane [69] 

37 Isopropyl p-nitrobenzoate -0.9 -1.5 35 60% dioxane [69] 

38 Butyl benzoate -2.3 -2.1 35 60% dioxane [69] 

39 Butyl p-aminobenzoate -3.8 -3.6 35 60% dioxane [69] 

40 Isobutyl benzoate -2.4 -2.1 35 60% dioxane [69] 

55
Num Esters Obs. Calc. Temp Solvent Ref. 

41 Isobutyl p-aminobenzoate -3.8 -3.6 35 60% dioxane [69] 

42 sec-Butyl benzoate -3.1 -3.2 35 60% dioxane [69] 

43 sec-Butyl m-methylbenzoate -3.3 -3.4 35 60% dioxane [69] 

44 Isopentyl benzoate -2.4 -1.8 35 60% dioxane [69] 

45 Isopentyl p-chlorobenzoate -1.8 -1.7 35 60% dioxane [69] 

46 Benzyl benzoate -1.8 -1.1 35 60% dioxane [69] 

47 Benzyl p-methylbenzoate -2.2 -1.7 35 60% dioxane [69] 

48 1-Phenyl-ethyl benzoate -2.1 -2.8 35 60% dioxane [69] 

49 1,1-Biphenyl-methyl benzoate -3.6 -4.7 35 60% dioxane [69] 

50 Ethyl p-methoxybenzoate -2.7 -2.9 35 60% dioxane [69] 

51 Ethyl p-fluorobenzoate -1.8 -1.9 35 60% dioxane [69] 

52 Ethyl m-nitrobenzoate -0.5 -1.2 35 60% dioxane [69] 

53 Ethyl p-nitrobenzoate -0.3 -1 35 60% dioxane [69] 

54 Ethyl 3,4-dinitrobenzoate -1.2 -0.4 35 60% dioxane [69] 

55 Ethyl p-aminobenzoate -3.5 -3.5 35 60% dioxane [69] 

56 Methyl benzoate -2.4 -2.4 10 60% dioxane [65] 

57 Methyl m-bromobenzoate -1.7 -2.1 10 60% dioxane [65] 

58 Methyl p-bromobenzoate -1.8 -2.3 10 60% dioxane [65] 

59 Methyl p-methoxybenzoate -3.1 -3.5 10 60% dioxane [65] 

60 Methyl m-methoxybenzoate -2.3 -2.7 10 60% dioxane [65] 

61 Methyl p-methylbenzoate -2.8 -3 10 60% dioxane [65] 

62 Methyl m-methylbenzoate -2.6 -2.7 10 60% dioxane [65] 

63 Methyl p-nitrobenzoate -0.5 -1.4 10 60% dioxane [65] 

64 Methyl m-nitrobenzoate -0.8 -1.6 10 60% dioxane [65] 

65 Methyl p-trifluoromethylbenzoate -1.2 -2.7 10 60% dioxane [65] 

66 Methyl benzoate -2.5 -2.2 10 60% dioxane [63] 

67 Methyl benzoate -1.9 -1.9 25 60% dioxane [63] 

68 Methyl o-methylbenzoate -2.8 -2.8 25 60% dioxane [63] 

69 Methyl o-methylbenzoate -2.3 -2.5 40.2 60% dioxane [63] 

70 Methyl o-methylbenzoate -2 -2.3 50.4 60% dioxane [63] 

71 Methyl o-ethylbenzoate -3.1 -2.9 30 60% dioxane [63] 

72 Methyl o-ethylbenzoate -2.7 -2.7 40 60% dioxane [63] 

73 Methyl o-ethylbenzoate -2.4 -2.5 50 60% dioxane [63] 

74 Methyl o-isopropylbenzoate -2.9 -2.8 40.9 60% dioxane [63] 

75 Methyl o-isopropylbenzoate -2.5 -2.6 49.9 60% dioxane [63] 

76 Methyl o-isopropylbenzoate -2.3 -2.4 60 60% dioxane [63] 

77 Methyl o-isopropylbenzoate -2 -2.3 70 60% dioxane [63] 

78 Methyl o-(t-butyl)benzoate -3.1 -1.7 114.6 60% dioxane [63] 

79 Methyl o-(t-butyl)benzoate -2.7 -1.6 124.1 60% dioxane [63] 

80 Methyl o-(t-butyl)benzoate -2.5 -1.5 133.7 60% dioxane [63] 

81 Methyl o-(t-butyl)benzoate -2.2 -1.4 144.3 60% dioxane [63] 

82 Ethyl benzoate -2 -1.7 30 60% dioxane [59] 

56
Num Esters Obs. Calc. Temp Solvent Ref. 

83 Ethyl benzoate -2.3 -2.2 30 70% dioxane [59] 

84 Ethyl p-nitrobenzoate -1.2 -1.1 30 60% dioxane [59] 

85 Ethyl p-nitrobenzoate -1.3 -1.2 30 70% dioxane [59] 

86 Benzyl benzoate -1.9 -1 30 50% dioxane [59] 

87 Benzyl benzoate -2.1 -1.5 30 70% dioxane [59] 

88 Methyl nicotinate -0.9 -1 10 65% dioxane [59] 

89 Methyl picolinate -0.7 -0.7 10 65% dioxane [59] 

90 Methyl isonicotinate -0.1 -0.9 10 65% dioxane [59] 

57
Table 7. SPARC-calculated vs. observed log base-catalyzed hydrolysis rate constants -1 for carboxylic acid esters in acetonitrile-water mixtures as a function of temperature in M-1s 

Esters Obs. Calc. Temp. Solvent Ref. 

1 p-Tolyl p-dimethylaminobenzoate -3.1 -2.6 25 33% Acetonitrile [70] 

2 p-Tolyl p-methylbenzoate -1.9 -1.6 25 33% Acetonitrile [70] 

3 p-Tolyl benzoate -1.5 -1 25 33% Acetonitrile [70] 

4 p-Tolyl p-chlorobenzoate -1 -1 25 33% Acetonitrile [70] 

5 p-Tolyl p-nitrobenzoate 0.2 -0.1 25 33% Acetonitrile [70] 

6 Phenyl p-dimethylaminobenzoate -2.9 -2.5 25 33% Acetonitrile [70] 

7 Phenyl p-methylbenzoate -1.6 -1.5 25 33% Acetonitrile [70] 

8 Phenyl benzoate -1.3 -0.9 25 33% Acetonitrile [70] 

9 Phenyl p-chlorobenzoate -0.8 -0.8 25 33% Acetonitrile [70] 

10 Phenyl p-nitrobenzoate 0.3 0.1 25 33% Acetonitrile [70] 

11 p-Chlorophenyl p-methylbenzoate -1.3 -1.3 25 33% Acetonitrile [70] 

12 p-Chlorophenyl benzoate -0.9 -0.8 25 33% Acetonitrile [70] 

13 p-Chlorophenyl p-chlorobenzoate -0.5 -0.7 25 33% Acetonitrile [70] 

14 p-Chlorophenyl p-nitrobenzoate 0.7 0.2 25 33% Acetonitrile [70] 

15 m-Nitrophenyl p-dimethylaminobenzoate -2.1 -1.9 25 33% Acetonitrile [70] 

16 m-Nitrophenyl p-methylbenzoate -0.7 -0.9 25 33% Acetonitrile [70] 

17 m-Nitrophenyl benzoate -0.3 -0.3 25 33% Acetonitrile [70] 

18 m-Nitrophenyl p-chlorobenzoate 0.1 -0.2 25 33% Acetonitrile [70] 

19 m-Nitrophenyl p-nitrobenzoate 1.2 0.7 25 33% Acetonitrile [70] 

20 p-Nitrophenyl p-dimethylaminobenzoate -1.8 -1.8 25 33% Acetonitrile [70] 

21 p-Nitrophenyl p-methylbenzoate -0.5 -0.8 25 33% Acetonitrile [70] 

22 p-Nitrophenyl benzoate -0.1 -0.2 25 33% Acetonitrile [70] 

23 p-Nitrophenyl p-chlorobenzoate 0.3 -0.1 25 33% Acetonitrile [70] 

24 p-Nitrophenyl p-nitrobenzoate 1.4 0.8 25 33% Acetonitrile [70] 

58
Table 8. SPARC-calculated vs. observed log acid-catalyzed hydrolysis rate constants -1 for carboxylic acid esters in water as a function of temperature in M-1s 

Num Esters Obs. Calc. Temp. Ref. 

1 Ethyl acetate -4 -3.9 25 [27, 71] 

2 Ethyl propionate -4 -4.3 25 [27, 71] 

3 Ethyl cyclo-butyl carboxylate -4 -4.7 25 [27, 71] 

4 Ethyl butyrate -4.3 -4.4 25 [27, 71] 

5 Ethyl pentate -4.4 -4.5 25 [27, 71] 

6 Ethyl hexanoate -4.4 -4.5 25 [27, 71] 

7 Ethyl iso-hexanoate -4.3 -4.4 25 [27, 71] 

8 Ethyl (heptyl)acetate -4.3 -4.5 25 [27, 71] 

9 Ethyl (t-butyl)propionate -4.3 -4.9 25 [27, 71] 

10 Ethyl sec-butyrate -4.4 -4.6 25 [27, 71] 

11 Ethyl cyclopentate -4.5 -5 25 [27, 71] 

12 Ethyl cyclohexanoate -4.8 -5.1 25 [27, 71] 

13 Ethyl iso-pentate -4.9 -4.6 25 [27, 71] 

14 Ethyl cyclohexyl-acetate -4.9 -4.8 25 [27, 71] 

15 Ethyl sec-pentate -5.1 -5.1 25 [27, 71] 

16 Ethyl cycloheptyl-carboxylate -5 -5.1 25 [27, 71] 

17 Ethyl neopentate -5.5 -5.2 25 [27, 71] 

18 Ethyl (t-butyl) acetate -5.7 -5.4 25 [27, 71] 

19 Ethyl (t-butyl)-sec-butyrate -5.8 -5.7 25 [27, 71] 

20 Ethyl (2-ethyl)butyrate -5.9 -5.9 25 [27, 71] 

21 Ethyl (2-propyl)pentate -6.1 -6.2 25 [27, 71] 

22 Ethyl (2-isobutyl-4-methyl)pentate -6.4 -6.7 25 [27, 71] 

23 Ethyl (t-butyl)neopentate -6.5 -6.5 25 [27, 71] 

24 Ethyl (2-neopentyl-4,4-dimethyl)pentate -7.2 -7.1 25 [27, 71] 

25 Ethyl (t-butyl)isopropionate -7.3 -6.6 25 [27, 71] 

26 Ethyl (t-butyl)t-butyrate -7.9 -7.1 25 [27, 71] 

27 Ethyl (2,2-diethyl)butyrate -7.8 -6.8 25 [27, 71] 

28 Ethyl (methyl )(neopentyl) (t-butyl) acetate -8 -8.4 25 [27, 71] 

29 Isopropyl formate -3 -3.5 25 [27, 71] 

30 Isopropyl acetate -4.2 -4.2 25 [27, 71] 

31 Isopropyl propionate -4.3 -4.5 25 [27, 71] 

32 Isopropyl chloroacetate -4.4 -4.8 25 [27, 71] 

33 Isopropyl butyrate -4.6 -4.7 25 [27, 71] 

34 Isopropyl pentate -4.6 -4.7 25 [27, 71] 

35 Isopropyl hexanoate -4.6 -4.8 25 [27, 71] 

36 Isopropyl iso-hexanoate -4.6 -4.7 25 [27, 71] 

37 Isopropyl phenylacetate -4.6 -4.8 25 [27, 71] 

38 Isopropyl phenylpropionate -4.6 -4.8 25 [27, 71] 

39 Isopropyl phenylbutyrate -4.7 -4.7 25 [27, 71] 

40 Isopropyl isobutyrate -4.7 -4.9 25 [27, 71] 

59
Num Esters Obs. Calc. Temp. Ref. 

41 Isopropyl cyclohexyl-carboxylate -5 -5.3 25 [27, 71] 

42 Isopropyl isopentate -5.1 -4.9 25 [27, 71] 

43 Isopropyl cyclohexylacetate -5.2 -5 25 [27, 71] 

44 Isopropyl (2-ethyl) propionate -5.3 -5.4 25 [27, 71] 

45 Isopropyl (2,2-methyl-phenyl) acetate -5.4 -5.6 25 [27, 71] 

46 Isopropyl (2,2-ethyl-phenyl) acetate -5.7 -6.1 25 [27, 71] 

47 Isopropyl neopentate -5.8 -5.4 25 [27, 71] 

48 Isopropyl (2,2-diphenyl) acetate -6 -6.7 25 [27, 71] 

49 Isopropyl (2-ethyl) butyrate -6.2 -6.1 25 [27, 71] 

50 Isopropyl (3-phenyl)-2-propenoate -6.2 -5.9 25 [27, 71] 

51 Isopropyl trichloroacetate -6.3 -5.8 25 [27, 71] 

52 Isopropyl benzoate -6.8 -6.2 25 [27, 71] 

53 Isopropyl cyclobutyl-carboxylate -4.3 -5 25 [27, 71] 

54 Isopropyl methoxyacetate -4.4 -4.9 25 [27, 71] 

55 Isopropyl bromoacetate -4.5 -4.9 25 [27, 71] 

56 Isopropyl thiolpropionate -4.6 -4.9 25 [27, 71] 

57 Isopropyl iodoacetate -4.6 -4.9 25 [27, 71] 

58 Isopropyl nonoate -4.5 -4.8 25 [27, 71] 

59 Isopropyl (4,4-dimethyl)pentate -4.6 -5.1 25 [27, 71] 

60 Isopropyl phenoxy-acetate -4.5 -4.9 25 [27, 71] 

61 Isopropyl cyclopentyl-carboxylate -4.7 -5.2 25 [27, 71] 

62 Isopropyl difluoroacetate -4.9 -5.1 25 [27, 71] 

63 Isopropyl methoxypropionate -5 -4.8 25 [27, 71] 

64 Isopropyl chloropropionate -5.1 -4.7 25 [27, 71] 

65 Isopropyl trifluoroacetate -5.4 -5.6 25 [27, 71] 

66 Isopropyl cycloheptyl-carboxylate -5.3 -5.3 25 [27, 71] 

67 Isopropyl dichloracetate -5.8 -5.2 25 [27, 71] 

68 Isopropyl neopentate -5.9 -5.4 25 [27, 71] 

69 Isopropyl (2-neopentyl)propionate -6.1 -5.9 25 [27, 71] 

70 Isopropyl dibromoacetate -6.1 -5.6 25 [27, 71] 

71 Isopropyl (2-propyl)pentate -6.3 -6.5 25 [27, 71] 

72 Isopropyl tribromoacetate -6.6 -6.4 25 [27, 71] 

73 Isopropyl (3,3-methyl-neopentyl)acetate -6.8 -6.7 25 [27, 71] 

74 Isopropyl (3-neopentyl-4,4-dimethyl)pentate -7.4 -7.4 25 [27, 71] 

75 Isopropyl (2-t-butyl)propionate -7.5 -6.8 25 [27, 71] 

76 Isopropyl (2,2-methyl-t-butyl)propionate -8.1 -7.4 25 [27, 71] 

77 Isopropyl (2,2-diethyl)butyrate -8 -7.1 25 [27, 71] 

78 Isopropyl (methyl) (neopentyl) (t-butyl)acetate -8.2 -8.6 25 [27, 71] 

79 n-Butyl formate -2.8 -3.5 25 [27, 71] 

80 n-Butyl acetate -4 -4 25 [27, 71] 

81 n-Butyl propionate -4.1 -4.3 25 [27, 71] 

82 n-Butyl chloroacetate -4.2 -4.6 25 [27, 71] 

60
Num Esters Obs. Calc. Temp. Ref. 

83 n-Butyl butyrate -4.4 -4.5 25 [27, 71] 

84 n-Butyl pentate -4.4 -4.5 25 [27, 71] 

85 n-Butyl hexanoate -4.4 -4.6 25 [27, 71] 

86 n-Butyl iso-hexanoate -4.4 -4.5 25 [27, 71] 

87 n-Butyl phenylacetate -4.4 -4.6 25 [27, 71] 

88 n-Butyl phenylpropionate -4.5 -4.6 25 [27, 71] 

89 n-Butyl phenylbutyrate -4.5 -4.5 25 [27, 71] 

90 n-Butyl isobutyrate -4.5 -4.7 25 [27, 71] 

91 n-Butyl cyclohexyl-carboxylate -4.8 -5.1 25 [27, 71] 

92 n-Butyl isopentate -5 -4.7 25 [27, 71] 

93 n-Butyl cyclohexylacetate -5 -4.8 25 [27, 71] 

94 n-Butyl (2-ethyl)propionate -5.2 -5.2 25 [27, 71] 

95 n-Butyl (2,2-methyl-phenyl)acetate -5.2 -5.4 25 [27, 71] 

96 n-Butyl (2,2-ethyl-phenyl)acetate -5.5 -5.9 25 [27, 71] 

97 n-Butyl neopentate -5.6 -5.2 25 [27, 71] 

98 n-Butyl (2,2-diphenyl)acetate -5.8 -6.5 25 [27, 71] 

99 n-Butyl (2-ethyl)butyrate -6 -5.9 25 [27, 71] 

100 n-Butyl (3-phenyl)2-propenoate -6 -5.7 25 [27, 71] 

101 n-Butyl trichloroacetate -6.1 -5.6 25 [27, 71] 

102 n-Butyl benzoate -6.6 -6 25 [27, 71] 

103 n-Butyl cyclobutyl-carboxylate -4.1 -4.8 25 [27, 71] 

104 n-Butyl methoxyacetate -4.2 -4.7 25 [27, 71] 

105 n-Butyl bromoacetate -4.3 -4.7 25 [27, 71] 

106 n-Butyl thiolpropionate -4.4 -4.7 25 [27, 71] 

107 n-Butyl iodoacetate -4.4 -4.7 25 [27, 71] 

108 n-Butyl nonoate -4.4 -4.6 25 [27, 71] 

109 n-Butyl (4,4-dimethyl) pentate -4.4 -5 25 [27, 71] 

110 n-Butyl phenoxy-acetate -4.4 -4.7 25 [27, 71] 

111 n-Butyl cyclopentyl-carboxylate -4.5 -5 25 [27, 71] 

112 n-Butyl difluoroacetate -4.7 -4.9 25 [27, 71] 

113 n-Butyl methoxypropionate -4.8 -4.6 25 [27, 71] 

114 n-Butyl chloropropionate -4.9 -4.5 25 [27, 71] 

115 n-Butyl trifluoroacetate -5.2 -5.4 25 [27, 71] 

116 n-Butyl cycloheptyl-carboxylate -5.1 -5.1 25 [27, 71] 

117 n-Butyl dichloracetate -5.6 -5 25 [27, 71] 

118 n-Butyl neopentate -5.8 -5.2 25 [27, 71] 

119 n-Butyl (2-neopentyl)propionate -5.9 -5.7 25 [27, 71] 

120 n-Butyl dibromoacetate -5.9 -5.4 25 [27, 71] 

121 n-Butyl (2-propyl) pentate -6.1 -6.3 25 [27, 71] 

122 n-Butyl tribromoacetate -6.5 -6.2 25 [27, 71] 

123 n-Butyl (3,3-methyl-neopentyl)acetate -6.6 -6.5 25 [27, 71] 

124 n-Butyl (3-neopentyl-4,4-dimethyl)pentate -7.2 -7.2 25 [27, 71] 

61
Num Esters Obs. Calc. Temp. Ref. 

125 n-Butyl (2-t-butyl) propionate -7.4 -6.7 25 [27, 71] 

126 n-Butyl (2,2-methyl-t-butyl) propionate -7.9 -7.2 25 [27, 71] 

127 n-Butyl (2,2-diethyl) butyrate -7.8 -6.9 25 [27, 71] 

128 (methyl) (neopentyl) (t-butyl)CC(=O)OCCCC -8 -8.4 25 [27, 71] 

129 Propyl formate -2.8 -3.5 25 [27, 71] 

130 Propyl acetate -4 -4 25 [27, 71] 

131 Propyl propionate -4.1 -4.3 25 [27, 71] 

132 Propyl chloroacetate -4.2 -4.6 25 [27, 71] 

133 Propyl butyrate -4.4 -4.5 25 [27, 71] 

134 Propyl pentate -4.4 -4.5 25 [27, 71] 

135 Propyl hexanoate -4.4 -4.5 25 [27, 71] 

136 Propyl iso-hexanoate -4.4 -4.5 25 [27, 71] 

137 Propyl phenylacetate -4.4 -4.6 25 [27, 71] 

138 Propyl phenylpropionate -4.5 -4.6 25 [27, 71] 

139 Propyl phenylbutyrate -4.5 -4.5 25 [27, 71] 

140 Propyl isobutyrate -4.5 -4.7 25 [27, 71] 

141 Propyl cyclohexyl-carboxylate -4.8 -5.1 25 [27, 71] 

142 Propyl isopentate -5 -4.7 25 [27, 71] 

143 Propyl cyclohexylacetate -5 -4.8 25 [27, 71] 

144 Propyl (2-ethyl)propionate -5.2 -5.2 25 [27, 71] 

145 Propyl (2,2-methyl-phenyl)acetate -5.2 -5.4 25 [27, 71] 

146 Propyl (2,2-ethyl-phenyl)acetate -5.5 -5.9 25 [27, 71] 

147 Propyl neopentate -5.6 -5.2 25 [27, 71] 

148 Propyl (2,2-diphenyl)acetate -5.8 -6.5 25 [27, 71] 

149 Propyl (2-ethyl)butyrate -6 -5.9 25 [27, 71] 

150 Propyl (3-phenyl)2-propenoate -6 -5.7 25 [27, 71] 

151 Propyl trichloroacetate -6.1 -5.6 25 [27, 71] 

152 Propyl benzoate -6.6 -6 25 [27, 71] 

153 Propyl cyclobutyl-carboxylate -4.1 -4.8 25 [27, 71] 

154 Propyl methoxyacetate -4.2 -4.7 25 [27, 71] 

155 Propyl bromoacetate -4.3 -4.7 25 [27, 71] 

156 Propyl thiolpropionate -4.4 -4.7 25 [27, 71] 

157 Propyl iodoacetate -4.4 -4.7 25 [27, 71] 

158 CCCCCCCCC(=O)OCCC -4.4 -4.6 25 [27, 71] 

159 Propyl (4,4-dimethyl)pentate -4.4 -4.9 25 [27, 71] 

160 Propyl phenoxy-acetate -4.4 -4.7 25 [27, 71] 

161 Propyl cyclopentyl-carboxylate -4.5 -5 25 [27, 71] 

162 Propyl difluoroacetate -4.7 -4.9 25 [27, 71] 

163 Propyl methoxypropionate -4.8 -4.6 25 [27, 71] 

164 Propyl chloropropionate -4.9 -4.5 25 [27, 71] 

165 Propyl trifluoroacetate -5.2 -5.4 25 [27, 71] 

166 Propyl cycloheptyl-carboxylate -5.1 -5.1 25 [27, 71] 

62
Num Esters Obs. Calc. Temp. Ref. 

167 Propyl dichloracetate -5.6 -5 25 [27, 71] 

168 Propyl neopentate -5.8 -5.2 25 [27, 71] 

169 Propyl (2-neopentyl)propionate -5.9 -5.7 25 [27, 71] 

170 Propyl dibromoacetate -5.9 -5.4 25 [27, 71] 

171 Propyl (2-propyl)pentate -6.1 -6.3 25 [27, 71] 

172 Propyl tribromoacetate -6.5 -6.2 25 [27, 71] 

173 Propyl (3,3-methyl-neopentyl)acetate -6.6 -6.5 25 [27, 71] 

174 Propyl (3-neopentyl-4,4-dimethyl)pentate -7.2 -7.2 25 [27, 71] 

175 Propyl (2-t-butyl)propionate -7.4 -6.6 25 [27, 71] 

176 Propyl (2,2-methyl-t-butyl)propionate -7.9 -7.2 25 [27, 71] 

177 Propyl (2,2-diethyl)butyrate -7.8 -6.9 25 [27, 71] 

178 (methyl) (neopentyl) (t-butyl)CC(=O)OCCC -8 -8.4 25 [27, 71] 

179 Methyl formate -2.7 -3.5 25 [27, 71] 

180 Methyl acetate -4 -3.8 25 [27, 71] 

181 Methyl propionate -4 -4.1 25 [27, 71] 

182 Methyl chloroacetate -4.2 -4.4 25 [27, 71] 

183 Methyl butyrate -4.3 -4.3 25 [27, 71] 

184 Methyl pentate -4.3 -4.3 25 [27, 71] 

185 Methyl hexanoate -4.4 -4.4 25 [27, 71] 

186 Methyl iso-hexanoate -4.3 -4.3 25 [27, 71] 

187 Methyl phenylacetate -4.3 -4.4 25 [27, 71] 

188 Methyl phenylpropionate -4.4 -4.4 25 [27, 71] 

189 Methyl phenylbutyrate -4.4 -4.3 25 [27, 71] 

190 Methyl isobutyrate -4.4 -4.5 25 [27, 71] 

191 Methyl cyclohexyl-carboxylate -4.8 -4.9 25 [27, 71] 

192 Methyl isopentate -4.9 -4.5 25 [27, 71] 

193 Methyl cyclohexylacetate -4.9 -4.6 25 [27, 71] 

194 Methyl (2-ethyl)propionate -5.1 -5 25 [27, 71] 

195 Methyl (2,2-methyl-phenyl)acetate -5.2 -5.2 25 [27, 71] 

196 Methyl (2,2-ethyl-phenyl)acetate -5.5 -5.7 25 [27, 71] 

197 Methyl neopentate -5.5 -5 25 [27, 71] 

198 Methyl (2,2-diphenyl)acetate -5.7 -6.3 25 [27, 71] 

199 Methyl (2-ethyl)butyrate -5.9 -5.7 25 [27, 71] 

200 Methyl (3-phenyl)2-propenoate -5.9 -5.5 25 [27, 71] 

201 Methyl trichloroacetate -6 -5.4 25 [27, 71] 

202 Methyl benzoate -6.5 -5.8 25 [27, 71] 

203 Methyl cyclobutyl-carboxylate -4 -4.6 25 [27, 71] 

204 Methyl methoxyacetate -4.2 -4.5 25 [27, 71] 

205 Methyl bromoacetate -4.2 -4.5 25 [27, 71] 

206 Methyl thiolpropionate -4.3 -4.5 25 [27, 71] 

207 Methyl iodoacetate -4.3 -4.5 25 [27, 71] 

208 CCCCCCCCC(=O)OC -4.3 -4.4 25 [27, 71] 

63
Num Esters Obs. Calc. Temp. Ref. 

209 Methyl (4,4-dimethyl)pentate -4.3 -4.7 25 [27, 71] 

210 Methyl phenoxy-acetate -4.3 -4.5 25 [27, 71] 

211 Methyl cyclopentyl-carboxylate -4.5 -5 25 [27, 71] 

212 Methyl difluoroacetate -4.6 -4.7 25 [27, 71] 

213 Methyl methoxypropionate -4.7 -4.4 25 [27, 71] 

214 Methyl chloropropionate -4.9 -4.3 25 [27, 71] 

215 Methyl trifluoroacetate -5.1 -5.2 25 [27, 71] 

216 Methyl cycloheptyl-carboxylate -5.1 -4.9 25 [27, 71] 

217 Methyl dichloracetate -5.5 -4.8 25 [27, 71] 

218 Methyl neopentate -5.7 -5 25 [27, 71] 

219 Methyl (2-neopentyl)propionate -5.8 -5.5 25 [27, 71] 

220 Methyl dibromoacetate -5.8 -5.2 25 [27, 71] 

221 Methyl (2-propyl)pentate -6.1 -6.1 25 [27, 71] 

222 Methyl tribromoacetate -6.4 -6 25 [27, 71] 

223 Methyl (3,3-methyl-neopentyl)acetate -6.5 -6.3 25 [27, 71] 

224 Methyl (3-neopentyl-4,4-dimethyl)pentate -7.1 -7 25 [27, 71] 

225 Methyl (2-t-butyl)propionate -7.3 -6.4 25 [27, 71] 

226 Methyl (2,2-methyl-t-butyl)propionate -7.9 -7 25 [27, 71] 

227 Methyl (2,2-diethyl)butyrate -7.8 -6.7 25 [27, 71] 

228 (methyl) (neopentyl) (t-butyl)CC(=O)OC -8 -8.2 25 [27, 71] 

229 Chloroethyl formate -2.8 -3.6 25 [27, 71] 

230 Chloroethyl acetate -4.1 -4.1 25 [27, 71] 

231 Chloroethyl propionate -4.2 -4.5 25 [27, 71] 

232 Chloroethyl chloroacetate -4.3 -4.7 25 [27, 71] 

233 Chloroethyl butyrate -4.4 -4.6 25 [27, 71] 

234 Chloroethyl pentate -4.5 -4.7 25 [27, 71] 

235 Chloroethyl hexanoate -4.5 -4.7 25 [27, 71] 

236 Chloroethyl iso-hexanoate -4.4 -4.6 25 [27, 71] 

237 Chloroethyl phenylacetate -4.5 -4.7 25 [27, 71] 

238 Chloroethyl phenylpropionate -4.5 -4.7 25 [27, 71] 

239 Chloroethyl phenylbutyrate -4.5 -4.6 25 [27, 71] 

240 Chloroethyl isobutyrate -4.6 -4.8 25 [27, 71] 

241 Chloroethyl cyclohexyl-carboxylate -4.9 -5.3 25 [27, 71] 

242 Chloroethyl isopentate -5 -4.8 25 [27, 71] 

243 Chloroethyl cyclohexylacetate -5.1 -4.9 25 [27, 71] 

244 Chloroethyl (2-ethyl)propionate -5.2 -5.3 25 [27, 71] 

245 Chloroethyl (2,2-methyl-phenyl)acetate -5.3 -5.5 25 [27, 71] 

246 Chloroethyl (2,2-ethyl-phenyl)acetate -5.6 -6 25 [27, 71] 

247 Chloroethyl neopentate -5.6 -5.4 25 [27, 71] 

248 Chloroethyl (2,2-diphenyl)acetate -5.8 -6.6 25 [27, 71] 

249 Chloroethyl (2-ethyl)butyrate -6.1 -6 25 [27, 71] 

250 Chloroethyl (3-phenyl)2-propenoate -6.1 -5.8 25 [27, 71] 

64
Num Esters Obs. Calc. Temp. Ref. 

251 Chloroethyl trichloroacetate -6.1 -5.7 25 [27, 71] 

252 Chloroethyl benzoate -6.6 -6.1 25 [27, 71] 

253 Chloroethyl cyclobutyl-carboxylate -4.1 -4.9 25 [27, 71] 

254 Chloroethyl methoxyacetate -4.3 -4.8 25 [27, 71] 

255 Chloroethyl bromoacetate -4.3 -4.8 25 [27, 71] 

256 Chloroethyl thiolpropionate -4.4 -4.8 25 [27, 71] 

257 Chloroethyl iodoacetate -4.4 -4.8 25 [27, 71] 

258 Chloroethyl nonatae -4.4 -4.7 25 [27, 71] 

259 Chloroethyl (4,4-dimethyl)pentate -4.4 -5.1 25 [27, 71] 

260 Chloroethyl phenoxy-acetate -4.4 -4.8 25 [27, 71] 

261 Chloroethyl cyclopentyl-carboxylate -4.6 -5.1 25 [27, 71] 

262 Chloroethyl difluoroacetate -4.8 -5 25 [27, 71] 

263 Chloroethyl methoxypropionate -4.8 -4.7 25 [27, 71] 

264 Chloroethyl chloropropionate -5 -4.7 25 [27, 71] 

265 Chloroethyl trifluoroacetate -5.2 -5.5 25 [27, 71] 

266 Chloroethyl cycloheptyl-carboxylate -5.2 -5.3 25 [27, 71] 

267 Chloroethyl dichloracetate -5.6 -5.1 25 [27, 71] 

268 Chloroethyl neopentate -5.8 -5.4 25 [27, 71] 

269 Chloroethyl (2-neopentyl)propionate -5.9 -5.9 25 [27, 71] 

270 Chloroethyl dibromoacetate -5.9 -5.5 25 [27, 71] 

271 Chloroethyl (2-propyl)pentate -6.2 -6.4 25 [27, 71] 

272 Chloroethyl tribromoacetate -6.5 -6.3 25 [27, 71] 

273 Chloroethyl (3,3-methyl-neopentyl) acetate -6.7 -6.6 25 [27, 71] 

274 Chloroethyl (3-neopentyl-4,4-dimethyl) pentate -7.3 -7.3 25 [27, 71] 

275 Chloroethyl (2-t-butyl)propionate -7.4 -6.8 25 [27, 71] 

276 Chloroethyl (2,2-methyl-t-butyl)propionate -8 -7.3 25 [27, 71] 

277 Chloroethyl (2,2-diethyl)butyrate -7.9 -7 25 [27, 71] 

278 (methyl) (neopentyl) (t-butyl)CC(=O)OCCCl -8.1 -8.6 25 [27, 71] 

279 Methoxymethyl formate -3.2 -3.8 25 [27, 71] 

280 Methoxymethyl acetate -4.5 -4.3 25 [27, 71] 

281 Methoxymethyl propionate -4.5 -4.6 25 [27, 71] 

282 Methoxymethyl chloroacetate -4.7 -4.9 25 [27, 71] 

283 Methoxymethyl butyrate -4.8 -4.8 25 [27, 71] 

284 Methoxymethyl pentate -4.9 -4.8 25 [27, 71] 

285 Methoxymethyl hexanoate -4.9 -4.8 25 [27, 71] 

286 Methoxymethyl iso-hexanoate -4.8 -4.8 25 [27, 71] 

287 Methoxymethyl phenylacetate -4.8 -4.9 25 [27, 71] 

288 Methoxymethyl phenylpropionate -4.9 -4.9 25 [27, 71] 

289 Methoxymethyl phenylbutyrate -4.9 -4.7 25 [27, 71] 

290 Methoxymethyl isobutyrate -4.9 -5 25 [27, 71] 

291 Methoxymethyl cyclohexyl-carboxylate -5.3 -5.4 25 [27, 71] 

292 Methoxymethyl isopentate -5.4 -4.9 25 [27, 71] 

65
Num Esters Obs. Calc. Temp. Ref. 

293 Methoxymethyl cyclohexylacetate -5.4 -5.1 25 [27, 71] 

294 Methoxymethyl (2-ethyl)propionate -5.6 -5.5 25 [27, 71] 

295 Methoxymethyl (2,2-methyl-phenyl)acetate -5.7 -5.7 25 [27, 71] 

296 Methoxymethyl (2,2-ethyl-phenyl)acetate -6 -6.2 25 [27, 71] 

297 Methoxymethyl neopentate -6 -5.5 25 [27, 71] 

298 Methoxymethyl (2,2-diphenyl)acetate -6.2 -6.8 25 [27, 71] 

299 Methoxymethyl (2-ethyl)butyrate -6.4 -6.2 25 [27, 71] 

300 Methoxymethyl (3-phenyl)2-propenoate -6.5 -6 25 [27, 71] 

301 Methoxymethyl trichloroacetate -6.5 -5.9 25 [27, 71] 

302 Methoxymethyl benzoate -7 -6.3 25 [27, 71] 

303 Methoxymethyl cyclobutyl-carboxylate * -4.5 -5.1 25 [27, 71] 

304 Methoxymethyl methoxyacetate -4.7 -5 25 [27, 71] 

305 Methoxymethyl bromoacetate -4.7 -5 25 [27, 71] 

306 Methoxymethyl thiolpropionate -4.8 -4.9 25 [27, 71] 

307 Methoxymethyl iodoacetate -4.8 -5 25 [27, 71] 

308 CCCCCCCCC(=O)OCOC -4.8 -4.9 25 [27, 71] 

309 Methoxymethyl (4,4-dimethyl)pentate -4.8 -5.2 25 [27, 71] 

310 Methoxymethyl phenoxy-acetate -4.8 -5 25 [27, 71] 

311 Methoxymethyl cyclopentyl-carboxylate -5 -5.3 25 [27, 71] 

312 Methoxymethyl difluoroacetate -5.1 -5.2 25 [27, 71] 

313 Methoxymethyl methoxypropionate -5.2 -4.9 25 [27, 71] 

314 Methoxymethyl chloropropionate -5.4 -4.8 25 [27, 71] 

315 Methoxymethyl trifluoroacetate -5.6 -5.7 25 [27, 71] 

316 Methoxymethyl cycloheptyl-carboxylate -5.6 -5.4 25 [27, 71] 

317 Methoxymethyl dichloracetate -6 -5.3 25 [27, 71] 

318 Methoxymethyl neopentate -6.2 -5.5 25 [27, 71] 

319 Methoxymethyl (2-neopentyl)propionate -6.3 -6 25 [27, 71] 

320 Methoxymethyl dibromoacetate -6.3 -5.7 25 [27, 71] 

321 Methoxymethyl (2-propyl)pentate -6.6 -6.6 25 [27, 71] 

322 Methoxymethyl tribromoacetate -6.9 -6.4 25 [27, 71] 

323 Methoxymethyl (3,3-methyl-neopentyl)acetate -7 -6.8 25 [27, 71] 

324 CC(C)(C)CC(CC(C)(C)C)C(=O)OCOC -7.7 -7.5 25 [27, 71] 

325 Methoxymethyl (2-t-butyl)propionate -7.8 -6.9 25 [27, 71] 

326 Methoxymethyl (2,2-methyl-t-butyl)propionate -8.4 -7.5 25 [27, 71] 

327 Methoxymethyl (2,2-diethyl)butyrate -8.3 -7.2 25 [27, 71] 

328 (methyl) (neopentyl) (t-butyl)CC(=O)OCOC -8.4 -8.9 25 [27, 71] 

329 Chloromethyl formate -3.2 -4 25 [27, 71] 

330 Chloromethyl acetate -4.4 -4.4 25 [27, 71] 

331 Chloromethyl propionate -4.5 -4.8 25 [27, 71] 

332 Chloromethyl chloroacetate -4.6 -5.1 25 [27, 71] 

333 Chloromethyl butyrate -4.8 -4.9 25 [27, 71] 

334 Chloromethyl pentate -4.8 -5 25 [27, 71] 

66
Num Esters Obs. Calc. Temp. Ref. 

335 Chloromethyl hexanoate -4.8 -5 25 [27, 71] 

336 Chloromethyl iso-hexanoate -4.8 -4.9 25 [27, 71] 

337 Chloromethyl phenylacetate -4.8 -5.1 25 [27, 71] 

338 Chloromethyl phenylpropionate -4.9 -5.1 25 [27, 71] 

339 Chloromethyl phenylbutyrate -4.9 -4.9 25 [27, 71] 

340 Chloromethyl isobutyrate -4.9 -5.2 25 [27, 71] 

341 Chloromethyl cyclohexyl-carboxylate -5.2 -5.6 25 [27, 71] 

342 Chloromethyl isopentate -5.4 -5.1 25 [27, 71] 

343 Chloromethyl cyclohexylacetate -5.4 -5.3 25 [27, 71] 

344 Chloromethyl (2-ethyl)propionate -5.6 -5.6 25 [27, 71] 

345 Chloromethyl (2,2-methyl-phenyl)acetate -5.6 -5.8 25 [27, 71] 

346 Chloromethyl (2,2-ethyl-phenyl)acetate -5.9 -6.4 25 [27, 71] 

347 Chloromethyl neopentate -6 -5.7 25 [27, 71] 

348 Chloromethyl (2,2-diphenyl)acetate -6.2 -6.9 25 [27, 71] 

349 Chloromethyl (2-ethyl)butyrate -6.4 -6.4 25 [27, 71] 

350 Chloromethyl (3-phenyl)2-propenoate -6.4 -6.2 25 [27, 71] 

351 Chloromethyl trichloroacetate -6.5 -6 25 [27, 71] 

352 Chloromethyl benzoate -7 -6.4 25 [27, 71] 

353 Chloromethyl cyclobutyl-carboxylate* -4.5 -5.2 25 [27, 71] 

354 Chloromethyl methoxyacetate -4.6 -5.1 25 [27, 71] 

355 Chloromethyl bromoacetate -4.7 -5.1 25 [27, 71] 

356 Chloromethyl thiolpropionate -4.8 -5.1 25 [27, 71] 

357 Chloromethyl iodoacetate -4.8 -5.2 25 [27, 71] 

358 Chloromethyl nonatae -4.8 -5 25 [27, 71] 

359 Chloromethyl (4,4-dimethyl) pentate -4.8 -5.4 25 [27, 71] 

360 Chloromethyl phenoxy-acetate -4.8 -5.1 25 [27, 71] 

361 Chloromethyl cyclopentyl-carboxylate -5 -5.5 25 [27, 71] 

362 Chloromethyl difluoroacetate -5.1 -5.3 25 [27, 71] 

363 Chloromethyl methoxypropionate -5.2 -5 25 [27, 71] 

364 Chloromethyl chloropropionate -5.3 -5 25 [27, 71] 

365 Chloromethyl trifluoroacetate -5.6 -5.9 25 [27, 71] 

366 Chloromethyl cycloheptyl-carboxylate -5.6 -5.6 25 [27, 71] 

367 Chloromethyl dichloracetate -6 -5.5 25 [27, 71] 

368 Chloromethyl neopentate -6.2 -5.7 25 [27, 71] 

369 Chloromethyl (2-neopentyl)propionate -6.3 -6.2 25 [27, 71] 

370 Chloromethyl dibromoacetate -6.3 -5.9 25 [27, 71] 

371 Chloromethyl (2-propyl)pentate -6.6 -6.8 25 [27, 71] 

372 Chloromethyl tribromoacetate -6.9 -6.6 25 [27, 71] 

373 Chloromethyl (3,3-methyl-neopentyl)acetate -7 -7 25 [27, 71] 

374 Chloromethyl (3-neopentyl-4,4-dimethyl)pentate -7.6 -7.6 25 [27, 71] 

375 Chloromethyl (2-t-butyl)propionate -7.8 -7.1 25 [27, 71] 

376 Chloromethyl (2,2-methyl-t-butyl)propionate -8.4 -7.6 25 [27, 71] 

67
Num Esters Obs. Calc. Temp. Ref. 

377 Chloromethyl (2,2-diethyl)butyrate -8.3 -7.3 25 [27, 71] 

378 (methyl) (neopentyl) (t-butyl)CC(=O)OCCl -8.4 -8.9 25 [27, 71] 

379 p-Nitrophenyl acetate -3.9 -3.9 30 [72] 

380 p-Nitrophenyl propionate -3.9 -4.3 30 [72] 

381 p-Nitrophenyl butyrate -4.1 -4.4 30 [72] 

382 p-Nitrophenyl isobutyrate -4.1 -4.6 30 [72] 

383 p-Nitrophenyl 3,3-dimethylbutyrate -4.8 -5.4 30 [72] 

68
-1 

Table 9. SPARC-calculated vs. observed log acid-catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-acetone mixtures as a function of temperature in M-1s 

Num Esters Obs Calc Temp Solvent Ref. 

1 Ethyl m-nitrobenzoate -7 -6.4 25 60% acetone [73] 

2 Ethyl benzoate -6.9 -6.3 25 60% acetone [73] 

3 Ethyl dichloroacetate -4.9 -5.2 25 60% acetone [73] 

4 Ethyl iso-butyrate -4.7 -4.9 25 60% acetone [73] 

5 Ethyl chloroacetate -4.4 -4.7 25 60% acetone [73] 

6 Methyl acetate -4.3 -3.7 25 60% acetone [73] 

7 Ethyl phenylacetate -4.8 -5 25 70% acetone [74] 

8 Ethyl phenylpropionate -4.9 -4.9 25 70% acetone [74] 

9 Ethyl phenylbutyrate -4.9 -4.6 25 70% acetone [74] 

10 Ethyl phenylpentate -4.8 -4.7 25 70% acetone [74] 

11 Ethyl phenylisopropionate -6.6 -6.3 25 70% acetone [74] 

12 Ethyl (2-ethyl)phenylacetate -6.9 -7.1 25 70% acetone [74] 

13 Ethyl (2,2-diphenyl)acetate -7.3 -8 25 70% acetone [74] 

14 Ethyl cyclohexylacetate -5.3 -5.2 25 70% acetone [74] 

15 Chloromethyl acetate -4.5 -4.4 25 70% acetone [74] 

16 Chloromethyl acetate -4.6 -4.4 25 70% acetone [74] 

17 Chloromethyl acetate -4.7 -4.4 25 70% acetone [74] 

18 Chloromethyl propionate -4.7 -4.9 25 70% acetone [74] 

19 Chloromethyl butyrate -5 -5.1 25 70% acetone [74] 

20 Ethyl acetate -4.3 -3.8 25 70% acetone [74] 

21 Ethyl propionate -4.4 -4.4 25 70% acetone [74] 

22 Ethyl butyrate -4.7 -4.7 25 70% acetone [74] 

23 Ethyl pentate -4.7 -4.8 25 70% acetone [74] 

24 Ethyl hexanoate -4.8 -4.8 25 70% acetone [74] 

25 Ethyl heptanoate -4.8 -4.8 25 70% acetone [74] 

26 Ethyl octanoate -4.8 -4.8 25 70% acetone [74] 

27 Ethyl isobutyrate -4.9 -5 25 70% acetone [74] 

28 Ethyl isopentate -5.2 -4.9 25 70% acetone [74] 

29 Ethyl hexanoate -4.8 -4.7 25 70% acetone [74] 

30 Ethyl sec-hexanoate -5.4 -6 25 70% acetone [74] 

31 Ethyl neopentate -5.9 -5.9 25 70% acetone [74] 

32 Ethyl (2-ethyl)butyrate -5.9 -6.8 25 70% acetone [74] 

33 Ethyl fluoroacetate -4.6 -4.7 25 70% acetone [74] 

34 Ethyl fluoroacetate -4.1 -4.3 35 70% acetone [74] 

35 Ethyl fluoroacetate -3.6 -3.8 50 70% acetone [74] 

36 Ethyl difluoroacetate -4 -5 25 70% acetone [74] 

37 Ethyl p-methoxybenzoate -5.7 -5.3 60 60% acetone [75] 

38 Ethyl p-methoxybenzoate -4.9 -4.7 80.2 60% acetone [75] 

39 Ethyl p-methoxybenzoate -4.2 -4.2 99.2 60% acetone [75] 

40 Ethyl p-methoxybenzoate -3.6 -3.6 119.9 60% acetone [75] 

69
Num Esters Obs. Calc. Temp Solvent Ref. 

41 Ethyl p-methoxybenzoate -3 -3.2 138.5 60% acetone [75] 

42 Ethyl p-hydroxybenzoate -5 -4.7 80.2 60% acetone [75] 

43 Ethyl p-hydroxybenzoate -4.3 -4.1 99.8 60% acetone [75] 

44 Ethyl p-hydroxybenzoate -3.7 -3.6 120.2 60% acetone [75] 

45 Ethyl p-hydroxybenzoate -3.2 -3.2 138.9 60% acetone [75] 

46 Ethyl p-methylbenzoate -4.8 -4.5 80.3 60% acetone [75] 

47 Ethyl p-methylbenzoate -4.1 -4 100.05 60% acetone [75] 

48 Ethyl p-methylbenzoate -3.5 -3.5 120.5 60% acetone [75] 

49 Ethyl p-methylbenzoate -3 -3 138.9 60% acetone [75] 

50 Ethyl benzoate -4.7 -4.4 80.3 60% acetone [75] 

51 Ethyl benzoate -4 -3.9 100.2 60% acetone [75] 

52 Ethyl benzoate -3.4 -3.4 120.9 60% acetone [75] 

53 Ethyl benzoate -2.9 -2.9 139.3 60% acetone [75] 

54 Ethyl p-chlorobenzoate -4.7 -4.5 80.3 60% acetone [75] 

55 Ethyl p-chlorobenzoate -4.1 -3.9 99.85 60% acetone [75] 

56 Ethyl p-chlorobenzoate -3.4 -3.4 120.2 60% acetone [75] 

57 Ethyl p-chlorobenzoate -2.9 -3 139.4 60% acetone [75] 

58 Ethyl p-bromobenzoate -5.5 -5.1 60.05 60% acetone [75] 

59 Ethyl p-bromobenzoate -4.7 -4.5 80.2 60% acetone [75] 

60 Ethyl p-bromobenzoate -4.1 -4 100.15 60% acetone [75] 

61 Ethyl p-bromobenzoate -3.5 -3.5 120.2 60% acetone [75] 

62 Ethyl p-bromobenzoate -3 -3 139.2 60% acetone [75] 

63 Ethyl p-nitrobenzoate -5.3 -5 60 60% acetone [75] 

64 Ethyl p-nitrobenzoate -4.6 -4.3 80.2 60% acetone [75] 

65 Ethyl p-nitrobenzoate -4 -3.8 99.4 60% acetone [75] 

66 Ethyl p-nitrobenzoate -3.4 -3.3 120 60% acetone [75] 

67 Ethyl p-nitrobenzoate -2.8 -2.9 138.5 60% acetone [75] 

68 Ethyl m-nitrobenzoate -5.4 -5.1 60 60% acetone [75] 

69 Ethyl m-nitrobenzoate -4.7 -4.4 80.2 60% acetone [75] 

70 Ethyl m-nitrobenzoate -4.1 -3.9 99.9 60% acetone [75] 

71 Ethyl m-nitrobenzoate -3.4 -3.4 120.4 60% acetone [75] 

72 Ethyl m-nitrobenzoate -2.9 -3 139 60% acetone [75] 

73 Ethyl o-nitrobenzoate -5.8 -5.2 80.3 60% acetone [75] 

74 Ethyl o-nitrobenzoate -5.2 -4.6 99.85 60% acetone [75] 

75 Ethyl o-nitrobenzoate -4.5 -4.1 120.7 60% acetone [75] 

76 Ethyl o-nitrobenzoate -4 -3.7 139.2 60% acetone [75] 

77 Ethyl butyrate -4.9 -4.9 20 70% acetone [74] 

78 Ethyl butyrate -4.5 -4.5 30 70% acetone [74] 

79 Ethyl butyrate -4.2 -4.1 40 70% acetone [74] 

80 Ethyl butyrate -3.8 -3.8 50 70% acetone [74] 

81 Ethyl pentate -4.9 -4.9 20 70% acetone [74] 

82 Ethyl pentate -4.6 -4.6 30 70% acetone [74] 

70
Num Esters Obs. Calc. Temp Solvent Ref. 

83 Ethyl pentate -4.2 -4.2 40 70% acetone [74] 

84 Ethyl pentate -3.8 -3.9 50 70% acetone [74] 

85 Ethyl isobutyrate -5.1 -5.2 20 70% acetone [74] 

86 Ethyl isobutyrate -4.7 -4.8 30 70% acetone [74] 

87 Ethyl isobutyrate -4.3 -4.5 40 70% acetone [74] 

88 Ethyl isobutyrate -3.9 -4.1 50 70% acetone [74] 

89 Ethyl sec-hexanoate -5.6 -6.2 20 70% acetone [74] 

90 Ethyl sec-hexanoate -5.2 -5.8 30 70% acetone [74] 

91 Ethyl sec-hexanoate -4.8 -5.5 40 70% acetone [74] 

92 Ethyl sec-hexanoate -4.4 -5.1 50 70% acetone [74] 

93 Ethyl iso-hexanoate -5 -4.9 20 70% acetone [74] 

94 Ethyl iso-hexanoate -4.6 -4.5 30 70% acetone [74] 

95 Ethyl iso-hexanoate -4.2 -4.2 40 70% acetone [74] 

96 Ethyl iso-hexanoate -3.8 -3.8 50 70% acetone [74] 

97 Ethyl cyclohexyl-carboxylate -5.3 -5.7 20 70% acetone [74] 

98 Ethyl cyclohexyl-carboxylate -4.9 -5.4 30 70% acetone [74] 

99 Ethyl cyclohexyl-carboxylate -4.6 -5 40 70% acetone [74] 

100 Ethyl cyclohexyl-carboxylate -4.2 -4.7 50 70% acetone [74] 

101 Ethyl acetate -3.6 -3.2 44.7 70% acetone [74] 

102 Ethyl propionate -3.7 -3.7 44.7 70% acetone [74] 

103 Ethyl butyrate -4 -4 44.7 70% acetone [74] 

104 Ethyl pentate -4 -4.1 44.7 70% acetone [74] 

105 Ethyl hexanoate -4 -4.1 44.7 70% acetone [74] 

106 Ethyl isobutyrate -4.1 -4.3 44.7 70% acetone [74] 

107 Ethyl isopentate -4.5 -4.3 44.7 70% acetone [74] 

108 Ethyl t-butyrate -4.9 -5.1 44.7 70% acetone [74] 

109 Ethyl phenylacetate -4 -4.4 44.7 70% acetone [74] 

110 Ethyl acetate -4 -3.5 35 70% acetone [74] 

111 Ethyl propionate -4 -4.1 35 70% acetone [74] 

112 Ethyl butyrate -4.3 -4.3 35 70% acetone [74] 

113 Ethyl pentate -4.3 -4.4 35 70% acetone [74] 

114 Ethyl hexanoate -4.4 -4.4 35 70% acetone [74] 

115 Ethyl isobutyrate -4.5 -4.6 35 70% acetone [74] 

116 Ethyl isopentate -4.8 -4.6 35 70% acetone [74] 

117 Ethyl t-butyrate -5.4 -5.5 35 70% acetone [74] 

118 Ethyl phenylacetate -4.1 -4.7 35 70% acetone [74] 

119 Ethyl phenylacetate -5 -5.2 20 70% acetone [74] 

120 Ethyl phenylpropionate -5.1 -5.1 20 70% acetone [74] 

121 Ethyl phenylbutyrate -5.1 -4.8 20 70% acetone [74] 

122 Ethyl phenylpentate -5.1 -4.9 20 70% acetone [74] 

123 Ethyl phenylisopropionate -6.8 -6.5 20 70% acetone [74] 

124 Ethyl 2-ethyl-2-phenylacetate -7.2 -7.3 20 70% acetone [74] 

71
Num Esters Obs. Calc. Temp Solvent Ref. 

125 Ethyl 2,2-diphenylacetate -7.5 -8.2 20 70% acetone [74] 

126 Ethyl cyclohexylacetate -5.5 -5.4 20 70% acetone [74] 

127 Ethyl phenylacetate -4.6 -4.8 30 70% acetone [74] 

128 Ethyl phenylpropionate -4.7 -4.8 30 70% acetone [74] 

129 Ethyl phenylbutyrate -4.7 -4.5 30 70% acetone [74] 

130 Ethyl phenylpentate -4.6 -4.5 30 70% acetone [74] 

131 Ethyl phenylisopropionate -6.3 -6.1 30 70% acetone [74] 

132 Ethyl 2-ethyl-2-phenylacetate -6.7 -6.9 30 70% acetone [74] 

133 Ethyl 2,2-diphenylacetate -7.1 -7.8 30 70% acetone [74] 

134 Ethyl cyclohexylacetate -5.1 -5 30 70% acetone [74] 

135 Ethyl phenylacetate -4.3 -4.5 40 70% acetone [74] 

136 Ethyl phenylpropionate -4.3 -4.4 40 70% acetone [74] 

137 Ethyl phenylbutyrate -4.3 -4.1 40 70% acetone [74] 

138 Ethyl phenylpentate -4.3 -4.1 40 70% acetone [74] 

139 Ethyl phenylisopropionate -6 -5.7 40 70% acetone [74] 

140 Ethyl 2-ethyl-2-phenylacetate -6.4 -6.6 40 70% acetone [74] 

141 Ethyl 2,2-diphenylacetate -6.7 -7.5 40 70% acetone [74] 

142 Ethyl cyclohexylacetate -4.7 -4.7 40 70% acetone [74] 

143 Ethyl phenylacetate -4.2 -4.2 50 70% acetone [74] 

144 Ethyl phenylpropionate -3.9 -4.1 50 70% acetone [74] 

145 Ethyl phenylbutyrate -4 -3.8 50 70% acetone [74] 

146 Ethyl phenylpentate -3.9 -3.8 50 70% acetone [74] 

147 Ethyl phenylisopropionate -5.6 -5.4 50 70% acetone [74] 

148 Ethyl 2-ethyl-2-phenylacetate -6 -6.2 50 70% acetone [74] 

149 Ethyl 2,2-diphenylacetate -6.3 -7.1 50 70% acetone [74] 

150 Ethyl cyclohexyl-acetate -4.3 -4.3 50 70% acetone [74] 

151 Benzyl acetate -4.9 -4.4 15 60% acetone [76] 

152 Benzyl acetate -4.5 -4 25 60% acetone [76] 

153 Benzyl acetate -3.9 -3.5 40 60% acetone [76] 

154 Benzyl acetate -3.2 -2.9 60 60% acetone [76] 

155 Benzyl acetate -2.6 -2.3 80 60% acetone [76] 

156 m-Methylbenzyl acetate -5 -4.4 15 60% acetone [76] 

157 m-Methylbenzyl acetate -4.5 -4 25 60% acetone [76] 

158 m-Methylbenzyl acetate -4 -3.5 40 60% acetone [76] 

159 m-Methylbenzyl acetate -3.3 -2.9 60 60% acetone [76] 

160 m-Methylbenzyl acetate -2.7 -2.3 80 60% acetone [76] 

161 p-Methylbenzyl acetate -4.5 -4 25 60% acetone [76] 

162 p-Methylbenzyl acetate -3.9 -3.5 40 60% acetone [76] 

163 p-Methylbenzyl acetate -3.2 -2.9 60 60% acetone [76] 

164 p-Methylbenzyl acetate -2.6 -2.4 80 60% acetone [76] 

165 m-Nitrobenzyl acetate -5 -4.4 15 60% acetone [76] 

166 m-Nitrobenzyl acetate -4.6 -4 25 60% acetone [76] 

72
Num Esters Obs. Calc. Temp Solvent Ref. 

167 m-Nitrobenzyl acetate -4 -3.5 40 60% acetone [76] 

168 m-Nitrobenzyl acetate -3.3 -2.9 60 60% acetone [76] 

169 m-Nitrobenzyl acetate -2.7 -2.4 80 60% acetone [76] 

170 p-Nitrobenzyl acetate -5 -4.4 15 60% acetone [76] 

171 p-Nitrobenzyl acetate -4.6 -4 25 60% acetone [76] 

172 p-Nitrobenzyl acetate -4 -3.5 40 60% acetone [76] 

173 p-Nitrobenzyl acetate -3.3 -2.9 60 60% acetone [76] 

174 p-Nitrobenzyl acetate -2.7 -2.4 80 60% acetone [76] 

175 Phenyl acetate -5 -4.6 15 60% acetone [76] 

176 Phenyl acetate -4.6 -4.3 25 60% acetone [76] 

177 Phenyl acetate -3.9 -3.8 40 60% acetone [76] 

178 Phenyl acetate -3.2 -3.1 60 60% acetone [76] 

179 Phenyl acetate -2.6 -2.6 80 60% acetone [76] 

180 m-Methylphenyl acetate -5 -4.7 15 60% acetone [76] 

181 m-Methylphenyl acetate -4.6 -4.3 25 60% acetone [76] 

182 m-Methylphenyl acetate -4 -3.8 40 60% acetone [76] 

183 m-Methylphenyl acetate -3.2 -3.2 60 60% acetone [76] 

184 m-Methylphenyl acetate -2.6 -2.6 80 60% acetone [76] 

185 p-Methylphenyl acetate -4.5 -4.3 25 60% acetone [76] 

186 p-Methylphenyl acetate -3.9 -3.8 40 60% acetone [76] 

187 p-Methylphenyl acetate -3.2 -3.2 60 60% acetone [76] 

188 p-Methylphenyl acetate -2.5 -2.6 80 60% acetone [76] 

189 m-Nitrophenyl acetate -5.2 -4.8 15 60% acetone [76] 

190 m-Nitrophenyl acetate -4.7 -4.4 25 60% acetone [76] 

191 m-Nitrophenyl acetate -4.1 -3.9 40 60% acetone [76] 

192 m-Nitrophenyl acetate -3.4 -3.2 60 60% acetone [76] 

193 m-Nitrophenyl acetate -2.8 -2.7 80 60% acetone [76] 

194 Ethyl dibromoacetate -4.7 -5.2 35 35% acetone [77] 

195 Ethyl dibromoacetate -4.8 -5.2 35 44% acetone [77] 

196 Ethyl dibromoacetate -4.9 -5.3 35 51.5% acetone [77] 

197 Ethyl dibromoacetate -5.1 -5.4 35 62% acetone [77] 

198 Ethyl dibromoacetate -5.3 -5.6 35 82.5% acetone [77] 

199 Ethyl dibromoacetate -4.3 -4.8 45 35% acetone [77] 

200 Ethyl dibromoacetate -4.4 -4.9 45 42.5% acetone [77] 

201 Ethyl dibromoacetate -4.6 -4.9 45 52% acetone [77] 

202 Ethyl dibromoacetate -4.7 -5 45 62% acetone [77] 

203 Ethyl dibromoacetate -4.9 -5.2 45 82% acetone [77] 

204 Ethyl dibromoacetate -4.1 -4.6 55 35% acetone [77] 

205 Ethyl dibromoacetate -4.2 -4.7 55 42.5% acetone [77] 

206 Ethyl dibromoacetate -4.3 -4.7 55 52% acetone [77] 

207 Ethyl dibromoacetate -4.2 -4.8 55 62% acetone [77] 

208 Ethyl dibromoacetate -4.6 -5 55 81.5% acetone [77] 

73
-1 

Table 10. SPARC-calculated vs. observed log acid-catalyzed hydrolysis rate constants 

 for carboxylic acid esters in water-methanol mixtures as a function of temperature in M-1s 

Num Ester Obs Calc Temp. Solvent Ref. 

1 Ethyl p-methoxybenzoate -4 -4.2 99.85 60% methanol [75] 

2 Ethyl p-methoxybenzoate -3.4 -3.6 120.45 60% methanol [75] 

3 Ethyl p-methoxybenzoate -3 -3.2 138.5 60% methanol [75] 

4 Ethyl p-methoxybenzoate -2.6 -2.9 153.9 60% methanol [75] 

5 Ethyl benzoate -3.8 -3.9 100.2 60% methanol [75] 

6 Ethyl benzoate -3.3 -3.4 121.2 60% methanol [75] 

7 Ethyl benzoate -2.8 -3 139.2 60% methanol [75] 

8 Ethyl benzoate -2.5 -2.6 153.9 60% methanol [75] 

9 Ethyl p-nitrobenzoate -3.8 -3.8 100.12 60% methanol [75] 

10 Ethyl p-nitrobenzoate -3.2 -3.3 120.75 60% methanol [75] 

11 Ethyl p-nitrobenzoate -2.8 -2.9 138.4 60% methanol [75] 

12 Ethyl p-nitrobenzoate -2.5 -2.6 153 60% methanol [75] 

13 Methyl benzoate -3.7 -3.9 100.8 80% methanol [63] 

14 Methyl o-methylbenzoate -4.4 -4.5 100.8 80% methanol [63] 

15 Methyl o-ethylbenzoate -4.7 -4.6 100.8 80% methanol [63] 

16 Methyl o-fluorobenzoate -3.7 -4.4 100.8 80% methanol [63] 

17 Methyl o-chlorobenzoate -4.2 -4.5 100.8 80% methanol [63] 

18 Methyl o-bromobenzoate -4.3 -4.6 100.8 80% methanol [63] 

19 Methyl o-iodobenzoate -4.6 -4.7 100.8 80% methanol [63] 

20 Methyl m-methylbenzoate -3.8 -3.9 100.8 80% methanol [63] 

21 Methyl m-chlorobenzoate -3.8 -3.9 100.8 80% methanol [63] 

22 Methyl m-nitrobenzoate -3.9 -3.9 100.8 80% methanol [63] 

74
-1 

Table 11. SPARC-calculated vs. observed log acid-catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-ethanol mixtures as a function of temperature in M-1s 

Num Esters Obs Calc Temp Solvent Ref 

1 Ethyl p-methoxybenzoate -5.7 -5.5 60 60% ethanol [75] 

2 Ethyl p-methoxybenzoate -4.8 -4.8 80.2 60% ethanol [75] 

3 Ethyl p-methoxybenzoate -4.2 -4.3 99.4 60% ethanol [75] 

4 Ethyl p-methoxybenzoate -3.6 -3.7 119.9 60% ethanol [75] 

5 Ethyl p-methoxybenzoate -3.1 -3.3 138.1 60% ethanol [75] 

6 Ethyl p-hydroxybenzoate -5 -4.8 80.2 60% ethanol [75] 

7 Ethyl p-hydroxybenzoate -4.4 -4.3 99.5 60% ethanol [75] 

8 Ethyl p-hydroxybenzoate -3.7 -3.7 120 60% ethanol [75] 

9 Ethyl p-hydroxybenzoate -3.2 -3.3 138.5 60% ethanol [75] 

10 Ethyl p-methylbenzoate -5.5 -5.3 60.05 60% ethanol [75] 

11 Ethyl p-methylbenzoate -4.8 -4.7 80.25 60% ethanol [75] 

12 Ethyl p-methylbenzoate -4.1 -4.1 99.9 60% ethanol [75] 

13 Ethyl p-methylbenzoate -3.5 -3.6 120.3 60% ethanol [75] 

14 Ethyl p-methylbenzoate -3 -3.1 139.7 60% ethanol [75] 

15 Ethyl benzoate -5.4 -5.2 60 60% ethanol [75] 

16 Ethyl benzoate -4.7 -4.5 80.2 60% ethanol [75] 

17 Ethyl benzoate -4.1 -4 99.6 60% ethanol [75] 

18 Ethyl benzoate -3.5 -3.5 120.2 60% ethanol [75] 

19 Ethyl benzoate -2.9 -3.1 138.6 60% ethanol [75] 

20 Ethyl p-chlorobenzoate -4.7 -4.6 80.3 60% ethanol [75] 

21 Ethyl p-chlorobenzoate -4.1 -4.1 100 60% ethanol [75] 

22 Ethyl p-chlorobenzoate -3.5 -3.5 120.6 60% ethanol [75] 

23 Ethyl p-chlorobenzoate -3.1 -3.1 139.3 60% ethanol [75] 

24 Ethyl p-bromobenzoate -4.7 -4.6 80.2 60% ethanol [75] 

25 Ethyl p-bromobenzoate -4.1 -4.1 100 60% ethanol [75] 

26 Ethyl p-bromobenzoate -3.5 -3.6 120.2 60% ethanol [75] 

27 Ethyl p-bromobenzoate -3 -3.1 139.4 60% ethanol [75] 

28 Ethyl p-nitrobenzoate -4.5 -4.5 80.2 60% ethanol [75] 

29 Ethyl p-nitrobenzoate -4 -3.9 98.9 60% ethanol [75] 

30 Ethyl p-nitrobenzoate -3.5 -3.4 119.3 60% ethanol [75] 

31 Ethyl p-nitrobenzoate -3 -3 138 60% ethanol [75] 

32 Ethyl m-nitrobenzoate -4.7 -4.6 80.2 60% ethanol [75] 

33 Ethyl m-nitrobenzoate -4.1 -4 99.45 60% ethanol [75] 

34 Ethyl m-nitrobenzoate -3.5 -3.5 119.9 60% ethanol [75] 

35 Ethyl m-nitrobenzoate -3 -3.1 138.3 60% ethanol [75] 

36 Ethyl o-nitrobenzoate -5.8 -5.3 80.3 60% ethanol [75] 

37 Ethyl o-nitrobenzoate -5.2 -4.7 100 60% ethanol [75] 

38 Ethyl o-nitrobenzoate -4.6 -4.2 120.6 60% ethanol [75] 

39 Ethyl o-nitrobenzoate -4.1 -3.8 138.9 60% ethanol [75] 

75
-1 

Table 12. SPARC-calculated vs. observed log acid-catalyzed hydrolysis rate constants 

for carboxylic acid esters in water-dioxane mixtures as a function of temperature in M-1s 

Num Esters Obs Calc Temp Solvent Ref. 

1 Chloromethyl acetate -4.4 -4.4 25 10% dioxane [78] 

2 Chloromethyl acetate -4 -4.1 35 10% dioxane [78] 

3 Chloromethyl acetate -3.6 -3.7 45 10% dioxane [78] 

4 Chloromethyl acetate -4.5 -4.5 25 25% dioxane [78] 

5 Chloromethyl acetate -4.1 -4.1 35 25% dioxane [78] 

6 Chloromethyl acetate -3.7 -3.8 45 25% dioxane [78] 

7 Chloromethyl acetate -4.7 -4.6 25 50% dioxane [78] 

8 Chloromethyl acetate -4.3 -4.2 35 50% dioxane [78] 

9 Chloromethyl acetate -3.9 -3.9 45 50% dioxane [78] 

10 Chloromethyl acetate -4.9 -4.8 25 75% dioxane [78] 

11 Chloromethyl acetate -4.5 -4.5 35 75% dioxane [78] 

12 Chloromethyl acetate -4.1 -4.1 45 75% dioxane [78] 

13 Methyl benzoate -3.8 -4.1 100 60% dioxane [79] 

14 Methyl o-methylbenzoate -4.4 -4.8 100 60% dioxane [79] 

15 Methyl o-ethylbenzoate -4.7 -5 100 60% dioxane [79] 

76
-1 

Table 13. SPARC-calculated vs. observed log neutral hydrolysis rate constants 

for carboxylic acid esters in water as a function of temperature using different catalysts in M-1s 

Num Esters Obs Calc Catalyst Temp Ref 

1 Ethyl acetate -11.3 -12.1 water 25 [53] 

2 Vinyl acetate -8.7 -9 water 25 [53] 

3 Chloromethyl formate -5.8 -6.5 water 25 [53] 

4 Methyl chloroacetate -8.4 -8.5 water 25 [53] 

5 Methyl dichloroacetate -6.6 -6.9 water 25 [53] 

6 Ethyl dichloroacetate -7 -7 water 25 [53] 

7 Chloroethyl dichloroacetate -6.2 -6.4 water 25 [53] 

8 Methoxyethyl dichloroacetate -6.7 -6.7 water 25 [53] 

9 Methyl trichloroacetate -4.8 -5.5 water 25 [53] 

10 Methoxyethyl trichloroacetate -5 -5.3 water 25 [53] 

11 Ethyl difluoroacetate -6 -5.9 water 25 [49] 

12 Methyl trifluoroacetate -4.2 -4.1 water 25 [49] 

13 Ethyl trifluoroacetate -4.3 -4.2 water 25 [49] 

14 Isopropyl trifluoroacetate -4.2 -4.2 water 25 [49] 

15 t-Butyl trifluoroacetate -4.6 -4.4 water 25 [49] 

16 Chloromethyl chloroacetate -5.7 -5.6 water 25 [53] 

17 Phenyl acetate -9 -9.1 water 25 [53] 

18 p-Methylphenyl acetate -9.1 -9.4 water 25 [49] 

19 p-Chlorophenyl acetate -8.9 -8.9 water 25 [49] 

20 p-Nitrophenyl acetate -7.8 -8.2 water 25 [49] 

21 3,4-Dinitrophenyl acetate -7.1 -7.5 water 25 [49] 

22 2,4-Dinitrophenyl acetate -6.7 -6.5 water 25 [80] 

23 2,6-Dinitrophenyl acetate -6.6 -5.8 water 25 [49] 

24 p-Nitrophenyl chloroacetate -5.2 -4.7 water 25 [80] 

25 Phenyl dichloroacetate -4.5 -4 water 25 [80] 

26 Ethyl trifluoroacetate -4.6 -4.4 water 10 [49] 

27 Ethyl difluoroacetate -3.8 -3.5 aniline 25 [81] 

28 Ethyl difluoroacetate -3.2 -3 acetate 25 [81] 

29 Ethyl difluoroacetate -2 -2 imidazole 25 [81] 

30 Ethyl dichloroacetate -4.5 -4.5 formate 25 [81] 

31 Ethyl dichloroacetate -4.8 -4.6 aniline 25 [81] 

32 Ethyl dichloroacetate -3.7 -3.9 pyridine 25 [81] 

33 Ethyl dichloroacetate -3.5 -3.5 picoline4 25 [81] 

34 Ethyl dichloroacetate -4.3 -4.1 acetate 25 [81] 

35 Ethyl dichloroacetate -3.6 -3.7 succinate 25 [81] 

36 Ethyl dichloroacetate -2.9 -3.1 imidazole 25 [81] 

37 Ethyl chloroacetate -6.1 -5.7 acetate 25 [81] 

38 Ethyl chloroacetate -4.4 -4.7 imidazole 25 [81] 

39 Ethyl trichloroacetate -2.8 -2.3 aniline 25 [80] 

40 p-Nitrophenyl chloroacetate -1.9 -1.6 pyridine 25 [80] 

77
Num Esters Obs Calc Catalyst Temp Ref 

41 p-Nitrophenyl chloroacetate 0.2 -0.1 imidazole 25 [80] 

43 2,6-dinitrophenyl acetate -2.9 -2.9 acetate 25 [82] 

44 2,4-dinitrophenyl acetate -3.3 -3.6 acetate 25 [82] 

45 2,3-dinitrophenyl acetate -3.6 -3.8 acetate 25 [82] 

46 3,4-dinitrophenyl acetate -4 -4.6 acetate 25 [82] 

47 p-Nitrophenyl acetate -5.2 -5.3 acetate 25 [82] 

48 o-Nitrophenyl acetate -5.3 -4.5 acetate 25 [82] 

49 m-Nitrophenyl acetate -5.5 -5.4 acetate 25 [82] 

50 p-Chlorophenyl acetate -6 -6.1 acetate 25 [82] 

51 p-Methylphenyl acetate -6.6 -6.6 acetate 25 [82] 

78
Table 14. SPARC-calculated vs. observed log neutral hydrolysis rate constants for carboxylic acid -1 esters in water-acetone mixtures as a function of temperature using different catalysts in M-1s 

Num Esters Obs Calc Catalysts Temp. Solvent Ref. 

1 Chloromethyl chloroacetate -7.2 -7 water 25 50% acetone [53] 

2 Chloromethyl dichloroacetate -5.3 -5.4 water 25 50% acetone [80] 

3 Methyl trifluoroacetate -5.6 -6.4 water 25 70% acetone [83] 

4 Ethyl trifluoroacetate -6.1 -6.5 water 25 70% acetone [83] 

5 Propyl trifluoroacetate -6.3 -6.5 water 25 70% acetone [83] 

6 Butyl trifluoroacetate -6.4 -6.5 water 25 70% acetone [83] 

7 Pentyl trifluoroacetate -6.4 -6.5 water 25 70% acetone [83] 

8 Hexyl trifluoroacetate -6.5 -6.5 water 25 70% acetone [83] 

9 Isopropyl trifluoroacetate -7 -6.6 water 25 70% acetone [65] 

10 sec-Butyl trifluoroacetate -7.2 -6.8 water 25 70% acetone [65] 

11 sec-Pentyl trifluoroacetate -7.3 -6.9 water 25 70% acetone [65] 

12 sec-Hexyl trifluoroacetate -7.3 -7 water 25 70% acetone [65] 

13 Phenyl trifluoroacetate -3.5 -3.6 water 25 70% acetone [65] 

14 m-Methyl trifluoroacetate -3.7 -3.7 water 25 70% acetone [65] 

15 p-Methyl trifluoroacetate -3.8 -3.9 water 25 70% acetone [65] 

16 o-Methyl trifluoroacetate -4.1 -3.7 water 25 70% acetone [65] 

17 Ethyl pentafluoroacetate -7.3 -8 water 25 70% acetone [83] 

18 Ethyl heptafluoropropionate -7.6 -8.3 water 25 70% acetone [83] 

19 Chloromethyl dichloroacetate -6.3 -6 water -6.23 50% acetone [80] 

20 Chloromethyl dichloroacetate -6.1 -5.9 water 0 50% acetone [80] 

21 Chloromethyl dichloroacetate -5.9 -5.8 water 5 50% acetone [80] 

22 Chloromethyl dichloroacetate -5.7 -5.7 water 12 50% acetone [80] 

23 Chloromethyl dichloroacetate -5.5 -5.5 water 18 50% acetone [80] 

24 Chloromethyl dichloroacetate -5 -5.3 water 35 50% acetone [80] 

25 Chloromethyl dichloroacetate -4.8 -5.1 water 45 50% acetone [80] 

26 Ethyl trifluoroacetate -4.6 -4.4 Water 10 70% acetone [83] 

27 Isopropyl trifluoroacetate -6.7 -6.4 Water 35 70% acetone [84] 

28 Isopropyl trifluoroacetate -6.5 -6.2 Water 45 70% acetone [84] 

29 sec-Butyl trifluoroacetate -6.9 -6.6 Water 35 70% acetone [84] 

30 sec-Butyl trifluoroacetate -6.7 -6.5 Water 45 70% acetone [84] 

31 sec-Pentyl trifluoroacetate -7.1 -6.7 Water 35 70% acetone [84] 

32 sec-Pentyl trifluoroacetate -6.9 -6.5 Water 45 70% acetone [84] 

33 sec-Hexyl trifluoroacetate -7.1 -6.8 water 35 70% acetone [84] 

34 sec-Hexyl trifluoroacetate -6.8 -6.6 water 45 70% acetone [84] 

35 Phenyl trifluoroacetate -3.3 -3.5 water 35 70% acetone [84] 

36 Phenyl trifluoroacetate -3.2 -3.4 water 45 70% acetone [84] 

37 m-Methylphenyl trifluoroacetate -3.6 -3.6 water 35 70% acetone [84] 

38 m-Methylphenyl trifluoroacetate -3.4 -3.6 water 45 70% acetone [84] 

39 p-Methylphenyl trifluoroacetate -3.7 -3.8 water 35 70% acetone [84] 

40 p-Methylphenyl trifluoroacetate -3.5 -3.7 water 45 70% acetone [84] 

79
Num Esters Obs Calc Catalysts Temp. Solvent Ref. 

41 o-Methylphenyl trifluoroacetate -3.9 -3.7 water 35 70% acetone [84] 

42 o-Methylphenyl trifluoroacetate -3.7 -3.6 water 45 70% acetone [84] 

43 Methyl trifluoroacetate -5.4 -6.2 water 35 70% acetone [83] 

44 Methyl trifluoroacetate -5.3 -6 water 45 70% acetone [83] 

45 Ethyl trifluoroacetate -6 -6.3 water 35 70% acetone [83] 

46 Ethyl trifluoroacetate -5.8 -6.1 water 45 70% acetone [83] 

47 Propyl trifluoroacetate -6.1 -6.3 water 35 70% acetone [83] 

48 Propyl trifluoroacetate -5.9 -6.1 water 45 70% acetone [83] 

49 Butyl trifluoroacetate -6.2 -6.3 water 35 70% acetone [83] 

50 Butyl trifluoroacetate -6 -6.1 water 45 70% acetone [83] 

51 Pentyl trifluoroacetate -6.3 -6.3 water 35 70% acetone [83] 

52 Pentyl trifluoroacetate -6 -6.1 water 45 70% acetone [83] 

53 Hexyl trifluoroacetate -6.3 -6.3 water 35 70% acetone [83] 

54 Hexyl trifluoroacetate -6.1 -6.1 water 45 70% acetone [83] 

55 Ethyl pentafluoroacetate -7.1 -7.8 water 35 70% acetone [83] 

56 Ethyl pentafluoroacetate -6.8 -7.6 water 45 70% acetone [83] 

57 Ethyl heptafluoroacetate -7.4 -8.1 water 35 70% acetone [83] 

58 Ethyl heptafluoroacetate -7.1 -7.9 water 45 70% acetone [83] 

59 Ethyl dibromoacetate -8.4 -8 water 35 36% acetone [77] 

60 Ethyl dibromoacetate -8.8 -8.3 water 35 44% acetone [77] 

61 Ethyl dibromoacetate -9.1 -8.7 water 35 53% acetone [77] 

62 Ethyl dibromoacetate -10.5 -10 water 35 83% acetone [77] 

63 Ethyl dibromoacetate -9.6 -9.1 water 35 63% acetone [77] 

64 Ethyl dibromoacetate -8.2 -7.8 water 45 36% acetone [77] 

65 Ethyl dibromoacetate -8.6 -8.1 water 45 44% acetone [77] 

66 Ethyl dibromoacetate -8.9 -8.4 water 45 53% acetone [77] 

67 Ethyl dibromoacetate -9.2 -8.8 water 45 63% acetone [77] 

68 Ethyl dibromoacetate -10.2 -9.7 water 45 83% acetone [77] 

69 Ethyl dibromoacetate -8.1 -7.7 water 51 36% acetone [77] 

70 Ethyl dibromoacetate -8.4 -7.9 water 51 44% acetone [77] 

71 Ethyl dibromoacetate -8.7 -8.3 water 51 53% acetone [77] 

72 Ethyl dibromoacetate -9.1 -8.6 water 51 63% acetone [77] 

73 Ethyl dibromoacetate -10 -9.5 water 51 83% acetone [77] 

80
Table 15. SPARC-calculated vs. observed log neutral hydrolysis rate constants for carboxylic -1 acid esters in water-ethanol mixtures using different catalysts in M-1s 

No Esters Obs Calc Catalysts Temp. Solvent Ref. 

1 Ethyl trichloroacetate -6.3 -6.3 water 25 40% ethanol [81] 

2 Ethyl difluoroacetate -5.8 -5.9 water 25 3% ethanol [81] 

3 Ethyl difluoroacetate -5.9 -6 water 25 7 % ethanol [81] 

4 Ethyl difluoroacetate -6 -6.1 water 25 12% ethanol [81] 

5 Ethyl difluoroacetate -6.3 -6.2 water 25 22% ethanol [81] 

6 Ethyl difluoroacetate -6.4 -6.4 water 25 32% ethanol [81] 

7 Ethyl difluoroacetate -6.8 -6.8 water 25 52% ethanol [81] 

8 Ethyl difluoroacetate -7.1 -7.1 water 25 72% ethanol [81] 

9 Ethyl trichloroacetate -3.7 -3.4 acetate 25 40% ethanol [81] 

81
Table 16. SPARC-calculated vs. observed log neutral hydrolysis rate constants for carboxylic acid -1 esters in water-dioxane mixtures as a function of temperature using different catalysts in M-1s 

No Esters Obs Calc Catalysts Temp. Solv Ref. 

1 Methyl trichloroacetate -6.3 -7.7 water 25 50% dioxane [53] 

2 Trichloroethyl dichloroacetate -6.3 -6.6 water 25 50% dioxane [53] 

3 Methyl trifluoroacetate -5.3 -5.5 water 25 60% dioxane [53] 

4 Methyl trifluoroacetate -5.7 -5.8 water 10 70% dioxane [53] 

5 Ethyl trichloroacetate -7 -6.7 water 25 50% dioxane [53] 

6 Propyl trichloroacetate -7.2 -6.7 water 25 50% dioxane [53] 

7 Butyl trichloroacetate -7.2 -6.8 water 25 50% dioxane [53] 

8 Isopropyl trichloroacetate -7.8 -6.9 water 25 50% dioxane [53] 

9 Chloroethyl trichloroacetate -6.1 -6.2 water 25 50% dioxane [53] 

10 Methoxyethyl trichloroacetate -6.6 -6.4 water 25 50% dioxane [53] 

11 Methyl trifluoroacetate -5.3 -5.5 water 25 60% dioxane [53] 

12 Methyl trifluoroacetate -5.7 -5.8 water 25 70% dioxane [53] 

13 Methyl trifluoroacetate -6.5 -6.2 water 0 70% dioxane [85] 

14 Methyl trifluoroacetate -5.4 -5.4 water 44.6 70% dioxane [85] 

15 Methyl trifluoroacetate -6 -5.9 water 0 60% dioxane [85] 

16 Methyl trifluoroacetate -5.1 -5.3 water 34.8 60% dioxane [85] 

17 Methyl trifluoroacetate -4.9 -5.2 water 44.6 60% dioxane [85] 

82
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34 

35 

Table 17. SPARC-calculated vs. observed log hydrolysis rate constants for organophosphorus in -1 water in basic media in M-1s 

No Ester Obs Calc Temp Ref. 

Methyl-o-isopropylphosphonofluoridate 1.35 1.018 20 [86] 

1.412 1.146 25 [86] 

1.56 1.271 30 [86] 

1.627 1.393 35 [86] 

Phosphonofluoridic acid, methyl-, methyl ester 2.025 2.501 25 [86] 

2.274 2.722 35 [86] 

Phosphonofluoridic acid, methyl-, 3,3-dimethylbutyl ester 1.693 1.574 25 [86] 

1.979 1.807 35 [86] 

Phosphonofluoridic acid, (1-methylethyl)-, 1-methylethyl ester 0.307 0.731 25 [86] 

0.525 0.959 35 [86] 

Phosphonofluoridic acid, methyl-, ethyl ester 1.783 1.84 25 [86] 

2.049 2.076 35 [86] 

Phosphonofluoridic acid, methyl-, 2-bromoethyl ester 2.21 1.98 25 [86] 

2.479 2.21 35 [86] 

Phosphonofluoridic acid, methyl-, propyl ester 1.732 1.791 25 [86] 

1.979 2.026 35 [86] 

Phosphonofluoridic acid, ethyl-, 1-methylethyl ester 0.971 0.949 25 [86] 

1.225 1.187 35 [86] 

Diethyl ethylphosphonate -4.691 -4.59 30 [45] 

-4.36 -4.29 40 [45] 

-4.065 -4.01 50 [45] 

-3.05 -3.5 69.5 [45] 

-2.941 -3.39 73.9 [45] 

-2.675 -3.13 84.7 [45] 

-2.51 -2.97 91.3 [45] 

Phosphoric acid, diethyl 4-nitrophenyl ester -1.96 -2.01 25 [87] 

-1.787 -1.91 30 [87] 

-1.574 -1.79 37 [87] 

-1.336 -1.64 45 [87] 

Phosphoric acid, trimethyl ester -3.951 -3.64 35 [45] 

-3.603 -3.37 44.7 [45] 

-3.162 -2.97 60 [45] 

-2.952 -2.83 65.5 [45] 

-2.798 -2.74 69.3 [45] 

-2.706 -2.65 73 [45] 

83
No Ester Obs Calc Temp Ref. 

36 Diethyl methylphosphonate -3.796 -4.31 30 [45] 

37 -3.483 -4.01 40 [45] 

38 -3.194 -3.72 50 [45] 

39 -2.886 -3.44 60 [45] 

40 -2.717 -3.18 70 [45] 

41 -2.484 -2.92 80 [45] 

42 -2.249 -2.68 90 [45] 

43 Phosphonic acid, methyl-, dimethyl ester -2.136 -2.99 49.8 [45] 

44 -1.906 -2.71 60 [45] 

45 -1.65 -2.46 70 [45] 

46 -1.363 -2.21 79.8 [45] 

47 Phosphoric acid, ethyl bis(4-nitrophenyl) ester -1.446 -1.75 25 [45] 

48 Phosphoric acid, dimethyl 4-nitrophenyl ester -1.706 -1.99 15 [88] 

49 -1.409 -1.78 25 [88] 

50 -1.244 -1.69 30 [88] 

51 -1.039 -1.55 37 [88] 

52 -0.845 -1.41 45 [88] 

53 Phosphoric acid, diethyl 6-methyl-2-(1-methylethyl)-4­

pyrimidinyl ester 

-1.45 -1.55 10 [89] 

54 -1.12 -1.38 20 [89] 

55 -0.607 -1.05 40 [89] 

56 0.039 -0.75 60 [89] 

57 Phosphoric acid, 4-nitrophenyl dipropyl ester -2.526 -2.08 25 [88] 

58 -2.342 -1.99 30 [88] 

59 -2.176 -1.86 37 [88] 

60 -1.911 -1.72 45 [88] 

61 Phosphinic acid, dibutyl-, 4-nitrophenyl ester -0.119 -0.56 15 [90] 

62 0 -0.49 20 [90] 

63 0.149 -0.43 25 [90] 

64 Diisopropyl methylphosphonate -4.116 -3.71 80 [45] 

65 -3.941 -3.47 90 [45] 

66 Phosphonic acid, phenyl-, diethyl ester -2.651 -2.58 59.8 [45] 

67 -2.499 -2.46 65.7 [45] 

68 -2.298 -2.29 74.9 [45] 

69 -2.201 -2.21 79.4 [45] 

70 -2.038 -2.11 84.8 [45] 

71 -1.99 -2.03 89.1 [45] 

84
Num Ester Obs Calc Temp Ref. 

72 Phosphonic acid, propyl-, dipropyl ester -3.747 -3.15 95 [45] 

73 Phosphoric acid, dibutyl 4-nitrophenyl ester -2.559 -2.11 25 [88] 

74 -2.342 -2.02 30 [88] 

75 -2.156 -1.89 37 [88] 

76 -1.933 -1.75 45 [88] 

77 Phosphonic acid, butyl-, diethyl ester -3.434 -3.34 80.3 [45] 

78 -3.233 -3.09 91.2 [45] 

79 -3.018 -2.92 99 [45] 

80 -2.735 -2.9 100 [45] 

81 O,O-Diethyl-O-phenylphosphate -3.51 -2.96 25 [91] 

82 Phosphoric acid, diethyl 4-(methylthio) phenyl ester -3.306 -2.94 25 [91] 

83 Phosphonic acid, (chloromethyl)-, diethyl ester -2.901 -2.55 20 [90] 

84 -2.604 -2.32 30 [90] 

85 -2.313 -2.09 40 [90] 

86 Bis(1-methylethyl)phosphoric acid 4-nitrophenyl ester -3.177 -2.27 25 [88] 

87 -2.978 -2.18 30 [88] 

88 -2.767 -2.06 37 [88] 

89 -2.505 -1.92 45 [88] 

90 Phosphonic acid, methyl-, 1-methylethyl 4-nitrophenyl ester -0.714 -1.42 24.9 [86] 

91 -0.577 -1.33 29.9 [86] 

92 -0.367 -1.2 37 [86] 

93 -0.164 -1.06 45 [86] 

94 Phosphonic acid, methyl-, ethyl 4-nitrophenyl ester -2.222 -1.82 0 [45] 

95 -1.741 -1.5 15 [45] 

96 -1.398 -1.31 25 [45] 

97 Phosphoric acid, diethyl 2-nitrophenyl ester -1.654 -2.48 25 [91] 

98 Phosphoric acid, diethyl 3-nitrophenyl ester -2.195 -2.75 25 [91] 

99 Phosphinic acid, diethyl-, ethyl ester -3 -2.27 70 [92] 

100 -2.824 -2.05 80 [92] 

101 -2.67 -1.84 90 [92] 

102 -2.535 -1.68 98 [92] 

103 Phosphoric acid, 4-chlorophenyl diethyl ester -2.939 -2.9 25 [91] 

104 Phosphoric acid, diethyl 4-methoxyphenyl ester -3.553 -2.98 25 [91] 

105 Phosphoric acid, 4-cyanophenyl diethyl ester -2.196 -2.12 25 [91] 

106 Phosphoric acid, bis(2-methylpropyl) 4-nitrophenyl ester -2.204 -1.98 25 [88] 

107 -2.036 -1.88 30 [88] 

108 -1.825 -1.76 37 [88] 

85
No Ester Obs Calc Temp Ref. 

109 -1.591 -1.62 45 [88] 

110 Phosphoric acid, bis(1-methylpropyl) 4-nitrophenyl ester -3.317 -3.27 25 [88] 

111 -3.137 -3.19 30 [88] 

112 -2.914 -3.07 37 [88] 

113 -2.651 -2.94 45 [88] 

114 Phosphonic acid, ethyl-, isopropyl p-nitrophenyl ester -1.432 -1.68 24.9 [86] 

115 -1.28 -1.59 29.9 [86] 

116 -1.069 -1.47 37 [86] 

117 -0.867 -1.34 45 [86] 

118 Phosphonic acid, propyl-, isopropyl p-nitrophenyl ester -1.479 -1.82 24.9 [86] 

119 -1.345 -1.74 29.9 [86] 

120 -1.155 -1.62 37 [86] 

121 -0.954 -1.49 45 [86] 

122 Phosphonic acid, isopropyl-, isopropyl p-nitrophenyl ester -2.654 -1.95 24.9 [86] 

123 -2.504 -1.87 29.9 [86] 

124 -2.278 -1.75 37 [86] 

125 -2.05 -1.63 45 [86] 

126 Phosphonic acid, butyl-, isopropyl p-nitrophenyl ester -1.502 -1.87 24.9 [86] 

127 -1.384 -1.79 29.9 [86] 

128 -1.19 -1.67 37 [86] 

129 -0.957 -1.54 45 [86] 

130 Phosphonic acid, isobutyl-, isopropyl p-nitrophenyl ester -1.706 -1.99 24.9 [86] 

131 -1.569 -1.9 29.9 [86] 

132 -1.375 -1.79 37 [86] 

133 -1.175 -1.66 45 [86] 

134 Phosphonic acid, sec-butyl-, isopropyl p-nitrophenyl ester -2.741 -2.36 24.9 [86] 

135 -2.596 -2.27 29.9 [86] 

136 -2.377 -2.16 37 [86] 

137 -2.147 -2.04 45 [86] 

138 Phosphonic acid, pentyl-, isopropyl p-nitrophenyl ester -1.54 -1.89 24.9 [86] 

139 -1.393 -1.81 29.9 [86] 

140 -1.198 -1.69 37 [86] 

141 -0.979 -1.56 45 [86] 

142 Phosphinic acid, dipropyl-, 4-nitrophenyl ester -0.004 -0.46 15 [86] 

143 0.059 -0.39 20 [86] 

144 0.192 -0.32 25 [86] 

145 Phosphinic acid, diisopropyl-, p-nitrophenyl ester -0.944 -0.38 25 [86] 

86
No Ester Obs Calc Temp Ref. 

146 -0.774 -0.32 30 [86] 

147 -0.548 -0.24 37 [86] 

148 -0.322 -0.15 45 [86] 

149 Phosphinic acid, diisobutyl-, p-nitrophenyl ester -0.452 -0.79 15 [86] 

150 -0.329 -0.72 20 [86] 

151 -0.206 -0.66 25 [86] 

152 Phosphinic acid, dipentyl-, 4-nitrophenyl ester -0.167 -0.6 15 [86] 

153 -0.058 -0.53 20 [86] 

154 0.031 -0.46 25 [86] 

155 Phosphinic acid, di-sec-butyl-, p-nitrophenyl ester -1.19 -1.26 25 [86] 

156 -1.025 -1.2 30 [86] 

157 -0.8 -1.13 37 [86] 

158 -0.574 -1.06 45 [86] 

159 Phosphonic acid, methyl-, diphenyl ester -2.475 -2.68 0.1 [45] 

160 -1.927 -2.35 15 [45] 

161 -1.771 -2.22 21.5 [45] 

162 Phosphinic acid, diethyl-, 4-nitrophenyl ester 0.13 -0.18 15 [86] 

163 0.189 -0.1 20 [86] 

164 0.329 -0.04 25 [86] 

165 Phosphinic acid, dimethyl-, 4-nitrophenyl ester -0.244 0.111 15 [86] 

166 -0.087 0.194 20 [86] 

167 0.059 0.275 25 [86] 

168 Phosphinic acid, methylpropyl-, 4-nitrophenyl ester -0.548 -0.18 15 [86] 

169 -0.394 -0.11 20 [86] 

170 -0.26 -0.03 25 [86] 

171 -0.106 0.043 30 [86] 

172 Phosphinic acid, isopropylmethyl-, p-nitrophenyl ester -0.714 -0.07 25 [86] 

173 -0.577 -0 30 [86] 

174 -0.367 0.09 37 [86] 

175 -0.164 0.195 45 [86] 

176 Phosphinic acid, butylmethyl-, p-nitrophenyl ester -0.555 -0.23 15 [86] 

177 -0.402 -0.16 20 [86] 

178 -0.269 -0.08 25 [86] 

179 -0.144 -0.01 30 [86] 

180 Phosphinic acid, isobutylmethyl-, p-nitrophenyl ester -0.62 -0.35 15 [86] 

181 -0.473 -0.27 20 [86] 

182 -0.331 -0.2 25 [86] 

87
No Ester Obs Calc Temp Ref. 

183 -0.173 -0.13 30 [86] 

184 Phosphinic acid, sec-butylmethyl-, p-nitrophenyl ester -1.037 -0.58 20 [86] 

185 -0.901 -0.51 25 [86] 

186 -0.753 -0.45 30 [86] 

187 -0.571 -0.36 37 [86] 

188 Phosphoric acid, diethyl 3-methoxyphenyl ester -3.206 -2.9 25 [91] 

189 Phosphoric acid, diethyl 3-methylphenyl ester -3.452 -2.98 25 [91] 

190 Phosphinic acid, ethylmethyl-, 4-nitrophenyl ester -0.424 -0.04 15 [86] 

191 -0.278 0.038 20 [86] 

192 -0.15 0.114 25 [86] 

193 -0.031 0.188 30 [86] 

194 Phosphinic acid, methylpentyl-, p-nitrophenyl ester -0.591 -0.25 15 [86] 

195 -0.396 -0.17 20 [86] 

196 -0.26 -0.1 25 [86] 

197 -0.112 -0.03 30 [91] 

198 Phosphoric acid, 4-aminophenyl diethyl ester -3.614 -3.08 25 [91] 

199 Phosphoric acid, diethyl 4-ethylphenyl ester -3.488 -2.93 25 [91] 

200 Phosphoric acid, diethyl 4-(1-methylethyl)phenyl ester -3.473 -2.96 25 [91] 

201 Phosphoric acid, diethyl 4-iodophenyl ester -2.889 -2.9 25 [91] 

202 Phosphoric acid, 3-bromophenyl diethyl ester -2.781 -2.83 25 [91] 

203 Phosphoric acid, o-(dimethylamino)phenyl diethyl ester -3.829 -3.39 25 [91] 

204 Phosphoric acid, diethyl o-ethylphenyl ester -3.717 -3.3 25 [91] 

205 Phosphoric acid, diethyl 2-iodophenyl ester -2.717 -2.92 25 [91] 

206 Phosphoric acid, 2-bromophenyl diethyl ester -2.623 -2.89 25 [91] 

207 Phosphoric acid, 2-chlorophenyl diethyl ester -2.585 -2.83 25 [91] 

208 Phosphoric acid, diethyl 2-methoxyphenyl ester -3.436 -3.13 25 [91] 

209 Phosphoric acid, 4-(dimethylamino)phenyl diethyl ester -3.555 -3.07 25 [91] 

210 Phosphoric acid, 4-bromophenyl diethyl ester -2.899 -2.9 25 [91] 

211 Phosphoric acid, diethyl 2-(1-methylethyl)phenyl ester -3.765 -3.45 25 [91] 

212 Phosphoric acid, 4-acetylphenyl diethyl ester -2.49 -2.9 25 [91] 

213 Phosphonic acid, methyl-, mono(4-nitrophenyl) ester, ion(1-) -4.632 -4.68 30 [93] 

214 -4.206 -4.38 39.4 [93] 

215 -3.848 -4.05 50 [93] 

216 -3.495 -3.76 60 [93] 

217 Phosphonic acid, methyl-, monophenyl ester, ion(1-) -5.745 -5.3 39 [93] 

218 -4.9 -4.65 58.8 [93] 

219 -4.533 -4.35 68.5 [93] 

88
No Ester Obs Calc Temp Ref. 

220 -4.206 -4.07 78 [93] 

221 Phosphoric acid, 3-chlorophenyl diethyl ester -2.806 -2.84 25 [91] 

222 Phosphoric acid, diphenyl ester, ion(1-) -5.456 -4.23 75 [93] 

223 Phosphonic acid, methyl-, bis(2,2-dimethylpropyl) ester -4.319 -3.69 88 [45] 

224 Benzoic acid, monoanhydride with phosphoric acid, ion(2-) -2.141 -1.71 37 [94] 

225 Benzoic acid, dianhydride with phosphoric acid, ion(1-) 0.404 1.073 37 [94] 

89
1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

Table 18. SPARC-calculated vs. observed log acid hydrolysis rate constants of organophosphorus -1 in water in M-1s 

No Esters Temp. Obs. Calc. Ref 

Phosphoric acid, diethyl 1-phenylethenyl ester 25 -4.68 -4.66 [44]

 41.5 -4.05 -4.13 [44]

 54.7 -3.50 -3.74 [44]

 70.2 -2.73 -3.32 [44] 

Phosphoric acid, diethyl 1-(4-methoxyphenyl)ethenyl ester 25 -3.24 -3.24 [44]

 41.4 -2.46 -2.79 [44]

 54.4 -2.02 -2.46 [44] 

Phosphoric acid, diethyl 1-(4-methylphenyl)ethenyl ester 25 -4.03 -4.05 [44]

 41.5 -3.18 -3.56 [44]

 54.7 -2.83 -3.19 [44]

 70.2 -2.26 -2.79 [44] 

Phosphoric acid, diethyl 1-(4-bromophenyl)ethenyl ester 25 -5.03 -4.36 [44]

 41.5 -4.30 -3.85 [44]

 54.2 -3.72 -3.49 [44]

 54.7 -3.60 -3.47 [44]

 70.2 -3.21 -3.06 [44] 

Phosphoric acid, diethyl 1-(4-nitrophenyl)ethenyl ester 69.8 -4.45 -3.81 [44]

 84.9 -3.80 -3.41 [44]

 99 -3.19 -3.06 [44] 

Phosphoric acid, diethyl 1-(3-nitrophenyl)ethenyl ester 69.8 -4.16 -3.56 [44]

 85 -3.50 -3.16 [44]

 99 -2.92 -2.83 [44] 

Phosphonic acid, (1,1-dimethylethyl)-, dimethyl ester 120 -3.95 -2.98 [45] 

Phosphonic acid, methyl-, bis(2,2-dimethylpropyl) ester 103 -4.33 -3.83 [45]

 120 -3.66 -3.40 [45] 

Phosphonic acid, butyl-, bis(1-methylethyl) ester 96 -3.79 -3.81 [45]

 101 -3.68 -3.68 [45]

 114.7 -3.07 -3.34 [45] 

Phosphonic acid, (1,1-dimethylethyl)-, bis(1-methylethyl) ester 115.2 -2.79 -2.28 [45] 

Phosphonic acid, methyl-, ethyl 4-nitrophenyl ester 110.4 -4.12 -4.56 [45] 

Phosphonic acid, propyl-, bis(1-methylethyl) ester 96 -3.77 -3.81 [45]

 101 -3.56 -3.68 [45]

 107.3 -3.33 -3.52 [45]

 114 -3.04 -3.36 [45]

 114.7 -3.06 -3.34 [45] 

Phosphonic acid, butyl-, diethyl ester 110 -4.58 -3.45 [45]

 119.5 -4.17 -3.22 [45] 

Phosphonic acid, phenyl-, diethyl ester 105.2 -4.61 -4.49 [45]

 110.2 -4.45 -4.35 [45]

 114.7 -4.18 -4.23 [45]

 120.3 -3.98 -4.09 [45]

 122.6 -3.96 -4.03 [45] 

90
43 Diisopropyl methylphosphonate 93.6 -3.49 -4.07 [45] 

44 100.6 -3.20 -3.88 [45] 

45 109.9 -2.93 -3.64 [45] 

46 110 -2.85 -3.64 [45] 

47 115 -2.69 -3.52 [45] 

48 Phosphonic acid, ethyl-, bis(1-methylethyl) ester 92.5 -3.80 -3.91 [45] 

49 101 -3.40 -3.69 [45] 

50 105.3 -3.31 -3.58 [45] 

51 110.4 -3.11 -3.45 [45] 

52 114.7 -2.88 -3.35 [45] 

53 Phosphonic acid, methyl-, dimethyl ester 99.8 -4.72 -4.59 [45] 

54 104.4 -4.52 -4.47 [45] 

55 110 -4.29 -4.32 [45] 

56 114.3 -3.94 -4.20 [45] 

57 119.6 -3.77 -4.07 [45] 

58 Diethyl methylphosphonate 101 -4.75 -4.21 [45] 

59 108.8 -4.46 -4.00 [45] 

60 109.9 -4.25 -3.97 [45] 

61 115.3 -4.21 -3.84 [45] 

62 116.9 -4.10 -3.80 [45] 

63 119.5 -3.96 -3.73 [45] 

64 Diphosphoric acid 39.8 -4.93 -4.94 [46] 

65 42.07 -4.81 -4.86 [46] 

66 44.79 -4.67 -4.77 [46] 

67 49.77 -4.44 -4.61 [46] 

68 Triphosphoric acid 39.59 -4.43 -4.36 [46] 

69 42.04 -4.29 -4.29 [46] 

70 44.71 -4.20 -4.21 [46] 

71 48.95 -3.98 -4.08 [46] 

72 Phosphoric acid, monophenyl ester 100 -5.42 -5.95 [42] 

73 Phosphoric acid, mono(4-methylphenyl) ester 100 -5.22 -5.15 [42] 

74 Phosphoric acid, diethyl 4-nitrophenyl ester 70 -3.98 -4.58 [95] 

75 Phosphoric acid, diethyl 4-(methylsulfonyl)phenyl ester 70 -4.01 -3.48 [95] 

76 1,2,3-Propanetriol, 1-(dihydrogen phosphate) 72.3 -6.81 -6.41 [96] 

77 85.5 -6.28 -5.96 [96] 

78 100 -5.70 -5.50 [96] 

79 1,2-Propanediol, 1-(dihydrogen phosphate) 72 -6.82 -6.75 [96] 

80 87.7 -6.11 -6.21 [96] 

81 100 -5.37 -5.81 [96] 

82 1,2,3-propanetriol, 2-(dihydrogen phosphate) 100 -5.70 -4.90 [96] 

83 D-Glucose, 2-(dihydrogen phosphate) 100 -3.38 -3.95 [97] 

91
Table 19. SPARC-calculated vs. observed log neutral hydrolysis rate constants of organophosphorus -1 in water in M-1s 

No Esters Temp. Obs. Calc. Ref 

1 Triethyl phosphate 79.6 0.63 -0.15 [98] 

2 101 1.45 0.34 [98] 

3 

Phosphoramidic acid, (1-methylethyl)-, ethyl 3-methyl-4­

(methylthio)phenyl ester 5 -3.96 -2.66 [99] 

4 22 -3.33 -2.03 [99] 

5 32 -2.10 -1.68 [99] 

6 50 -1.66 -1.10 [99] 

7 Serine dihydrogen phosphate (ester) 80 -1.46 -1.12 [100] 

8 90 -0.97 -0.90 [100] 

9 100 -0.37 -0.70 [100] 

10 Benzoic acid, 4-methoxy-, monoanhydride with phosphoric acid 39 2.68 1.73 [101] 

11 39 -1.20 -0.15 [101] 

12 Benzoic acid, 3,5-dinitro-, anhydride with H3PO4 39 -0.65 -2.63 [101] 

13 Phosphoric acid, mono(4-methylphenyl) ester 39 2.84 1.54 [101] 

14 39 -1.12 -0.34 [101] 

15 73 -0.82 0.38 [42] 

16 80 -0.49 0.52 [42] 

17 89 0.01 0.68 [42] 

18 100 0.50 0.88 [42] 

19 Phosphoric acid, monophenyl ester 39 2.91 0.83 [101] 

20 39 -1.09 -1.05 [101] 

21 73 -0.71 -0.26 [42] 

22 75.6 -0.49 -0.20 [102] 

23 80 -0.39 -0.11 [42] 

24 89 0.09 0.07 [42] 

25 100 0.58 0.28 [42] 

26 Phosphoric acid, trimethyl ester 44.7 -0.27 -0.61 [37] 

27 65.5 0.72 -0.12 [37] 

28 73 1.04 0.04 [37] 

29 80 1.34 0.19 [37] 

30 100.1 2.09 0.59 [37] 

31 Phosphoric acid, mono (4-nitrophenyl) ester 39 3.87 2.42 [101] 

32 25 -2.94 0.25 [103] 

33 39 -0.97 0.54 [101] 

34 73 -0.20 1.17 [103] 

35 Phosphoric acid, mono(2-nitrophenyl) ester 25 -3.30 -1.38 [103] 

36 73 -0.43 -0.14 [103] 

37 100 2.53 0.44 [103] 

38 Phosphoric acid, mono (3-nitrophenyl) ester 25 -2.80 -2.24 [103] 

39 39 -0.96 -1.84 [101] 

40 73 -0.50 -0.97 [103] 

92
41 100 0.76 -0.38 [103] 

42 Phenol, 2-(1,1-dimethylethyl)-, dihydrogen phosphate 100 -0.30 -1.13 [103] 

43 Phenol, 2,6-dimethyl-, dihydrogen phosphate 73 -1.06 -0.56 [103] 

44 100 0.31 0.10 [103] 

45 

Phenol, 2,6-bis(1,1-dimethylethyl)-4-methyl-, dihydrogen 

phosphate 100 -0.38 0.97 

[103] 

46 Phosphoric acid, mono (4-chlorophenyl) ester 39 3.24 0.73 [101] 

47 39 -1.13 -1.14 [101] 

48 100 0.58 0.20 [103] 

49 Phenol, 4-(1,1-dimethylethyl)-, dihydrogen phosphate 100 0.35 0.68 [103] 

50 Phosphoric acid, mono (2-chlorophenyl) ester 73 -0.78 -1.01 [103] 

51 100 0.46 -0.38 [103] 

52 a-D-Glucopyranose, 1-(dihydrogen phosphate) 82 0.94 -0.22 [104] 

53 100.1 1.92 0.14 [104] 

54 82 -1.21 -1.84 [104] 

55 100.1 -0.29 -1.40 [104] 

56 Phosphoric acid, monomethyl ester 80 -1.97 -0.15 [105] 

57 89 -1.50 0.01 [105] 

58 100.1 -0.92 0.20 [105] 

59 109.7 -0.43 -0.62 [105] 

60 117.2 -0.09 0.47 [105] 

61 2-(Phosphonooxy) benzoic acid 25 2.36 2.23 [43] 

62 37.2 0.88 -0.16 [106] 

63 42 1.13 -0.04 [106] 

64 47.4 1.48 0.09 [106] 

65 

Phosphoric acid, diethyl 6-methyl-2-(1-methylethyl)-4-pyrimidinyl 

ester 20 0.84 1.02 [32] 

66 Diisopropyl methylphosphonate 70 -0.17 1.37 [47] 

67 81 0.38 1.58 [47] 

68 90 0.79 1.74 [47] 

69 98 1.12 1.88 [47] 

70 Phosphoric acid, monoethyl ester 100 -2.12 -0.55 [107] 

71 Phosphoric acid, diethyl 4-nitrophenyl ester 20 0.15 0.43 [32] 

72 70 1.03 1.61 [95] 

73 Phosphoric acid, diethyl 4-(methylsulfonyl)phenyl ester 70 1.10 1.30 [95] 

74 Dimethyl-2,2-dichlorovinyl phosphate 70 -0.20 -0.36 [95] 

75 Trichlorfon 70 3.14 2.78 [95] 

76 Phosphoric acid, dimethyl 4-nitrophenyl ester 24 0.74 0.15 [108] 

77 32 0.92 0.35 [108] 

78 40 1.90 0.55 [108] 

79 Phosphoric acid, mono(1-methylethyl) ester 72.2 -2.39 -1.63 [109] 

80 84.6 -1.58 -1.34 [109] 

81 100 -0.77 -1.00 [109] 

82 1,2-Propanediol, 1-(dihydrogen phosphate) 100 -0.66 -0.62 [96] 

83 Phenol, 2,4-dinitro-, dihydrogen phosphate (ester) 25 1.92 1.72 [103] 

84 39 0.70 -1.08 [110] 

85 1-Naphthalenol, dihydrogen phosphate 80 -1.01 -0.24 [106] 

93
86 2-Naphthalenol, dihydrogen phosphate 80.6 -0.57 0.91 [106] 

87 Benzoic acid, 3-(phosphonooxy)- 80 0.33 -0.14 [106] 

88 Benzoic acid, 4-(phosphonooxy)- 80 1.09 1.38 [106] 

89 1-Naphthoic acid, 8-hydroxy-, phosphate 80 -2.39 -0.42 [106] 

94
9. CONCLUSION 

SPARC’s chemical reactivity models, which are used to calculate both ionization pKa (in 

water, non-aqueous liquid and gases) and electron affinity, have been extended to calculate 

hydrolysis rate constants for carboxylic acid and organophosphate esters. These reactivity 

models have been tested to the maximum extent possible in a single and in a mixed solvent 

(organophosphorus only in water) as a function of temperature using all the reliable data found in 

the literature. 

The strength of the SPARC calculator is its ability to estimate the hydrolysis rate constants 

(as well many other properties) of interest for almost any molecular structure within an acceptable 

error, especially for molecules that are difficult to measure. However, the real test of SPARC does 

not lie in testing the predictive capability for hydrolysis rate constants, pKa's, or activity 

coefficient, but is determined by its extrapolatability to other types of chemistry. Further extension 

of the SPARC chemical reactivity models will be under development soon to calculate 

hydrolysis rate constants for other classes of organic compounds as a function of solvent and 

temperature. 

Finally, SPARC is an important tool in designing chemicals for specific properties, for 

use in preliminary evaluation of the risks associated with chemical release into the environment, 

and in chemical fate-modeling applications in the absence of experimentally measured values. 

The development of the SPARC chemical hydrolysis models (as well as its other physical and 

chemical properties estimation) directly address the EPA Office of Research and Development 

(ORD) long term research agenda for the agency’s Chemical Toxicology Initiative that 

emphasizes that EPA will rely heavily on predictive modeling to carry out the increasingly 

95
complex array of exposure and risk assessments necessary to develop scientifically defensible 

regulations. 

SPARC is online and can be used at http://ibmlc2.chem.uga.edu/sparc 

96
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100
 APPENDIX 

Figure 6. Sample calculations of log hydrolysis rate constant in acid catalyzed media for p-nitrophenyl 

acetate in water at 25o C. Only the reaction center parameters are trained on hydrolysis rate 

constant (at the top). The substituent, molecular conductor parameters and distances (r’s) 

between the various components are the same as of ionization pKa 

101
Carboxylic Acid Ester Hydrolysis Rate Constant Reaction Center Characteristic Parameters 

Reaction Center ρele ρares ρbres χc A MF A Ref 1 Ref2 ρFS ρSteric ρα ρβ 

Acid Hydrolysis -0.87 -0.4 1.11 1.80 -0.67 3.36 3.886 -3070.8 -3.0 * 105 -310935 -1821 944.6 

Base Hydrolysis 

4.5 -0.8 

3.90 2.55 -0.67 3.36 -3.522 -1443.4 0.18 * 107 -328642 -4205 2119 

GBase Hydrolysis 5.2 -0.6 2.59 2.65 -0.67 3.36 -5.249 -3479.7 -0.15 * 107 -114969 -373 5598 

log kc = 3.36 + log (298.15) + 3.886 + (-3070.8 / 298.15) = - 0.59 

⎢ ik ⎥ δ log k = ρ ⎡ NB (χ − χ ) + Fs cos θcs + MF A ∑ q + P σ ⎤ IPd + ρ Δq c elec ⎢ c s 3 S MF 2 jc π ⎥ res ⎣ rcs k rkc ⎢ ⎦⎥

⎡ 7.746×1 ⎛ 2 × 0.078 0.078 3× 0.078 ⎞ ⎤ δ log kc = − 0.87 ⎣⎢⎢0.65 (2.3 −1.8) + (1.3 + 2 +1) + 2.515 ( − 0.67) ⎝⎜⎜ (1.73 + 1.3) + 1.3 − (1.3 + 2 ) ⎠⎟⎟ +1×0.008 ⎦⎥⎥ + 0.28 × 1.1

IP 3 2 2 2 

r

jc

 r

14 (p-benzene) r is r13 (m-benzene) 

ρ ρ (V +V −V ) ρ α ρ β δ log k = FS + steric s ex thresh + A + B EP c Tk D e T k Tk 

damp 

T k + De 

δ log k = − 3 × 105 + − 310935 × 0.0687 + −1821× 0.384 + 944.6 × 0.382 = − 3.333 EP c 298.15 × 78.54 298.15 × 78.54 298.15 298.15 

Log k Hydrolysis = -0.59 + (-0.075) + (-3.33) = -3.995 (Observed is 3.9) 

a: for carbonyl of C, b: for the oxygen of C, c: for aromatic R-π unit, d: for ethylenic R-π unit. 

102