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DETERMINATION OF RATES OF REACTION 

IN THE GAS-PHASE IN THE TROPOSPHERE 

THEORY AND PRACTICE 

5. Rate of Indirect Photoreaction: Evaluation of the 

Atmospheric Oxidation Computer Program of Syracuse 

Research Corporation for Estimating the Second-Order 

Rate Constant for the Reaction of an Organic Chemical 

with Hydroxyl Radicals 

1 by 

Asa Leifer 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

OFFICE OF POLLUTION PREVENTION AND TOXICS 

WASHINGTON, DC 20460 
~- 

i CONTENTS 

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . xii 

I. Introduction . . . . . . . . . . . . . . . . . . 1 

II. Mathematical Synopsis of the Structure/Reactivity 

~ Relationships of Atkinson and Meylan ...... 3 

III. Syracuse Research Corporation Atmospheric 

Oxidation Computer Program (Developed by 

Meylan) . . . . . . . . . . . . . . . . . . . . 14 

III . A. Introduction . . . . . . . . . . . . . . . . . . 14 

III.B. Atmospheric Oxidation Computer Program (AOP) .. 15 

IV. Evaluation of the Atmospheric Oxidation 

Computer Program for Estimating kOH and 

the Experimentally Measured kO HData 

Listed in the Program . . . . . . . . . . . . . 29 

IV.A. Comments on the Group Rate Constants, 

Substituent Factors, and Other Parameters 

Used by the Atmospheric Oxidation Program ... 29 

IV.B. Some Comments on Hydroxyl Radical Addition to 

Heteroaromatic and Fused Polyaromatic Ring 

Systems . . . . . . . . . . . . . . . . . . . . 46 

IV.C. H-Atom Abstraction from C-H and -OH Groups by 

Hydroxyl Radicals . . . . . . . . . . . . . . . 52 

IV.C.1. Saturated Alkanes . . . . . . . . . . . . . . . 52 

IV.C.l.a. Evaluation of the Experimental kOg Data .... 52 

IV.C.i.b. Evaluation of the Estimated k OH Data ...... 57 

IV. C. 2. Haloalkanes . . . . . . . . . . . . . . . . . . 59 

IV.C.2.a. Evaluation of the Experimental kpH Data .... 59 

IV.C.2.b. Evaluation of the Estimated kOH Data ...... 62 

IV.C.3. Carbonyl Compounds . . . . . . . . . . . . . . . 62 

IV.C.3.a. Evaluation of the Experimental kpH Data .... 62 

IV.C.3.b. Evaluation of the Estimated kOH Data ...... 68 

ii 
IV.C.4. Alcohols, Glycols, Ethers, and Hydroperoxides . 71 

IV.C.4.a. Evaluation of the Experimental kOH Data .... 71 

IV.C.4.b. Evaluation of the Estimated kOH Data ...... 71 

IV.C.5. Alkyl Nitrates and Nitriles . . . . . . . . . . 79 

IV.C.5.a. Evaluation of the Experimental kOH Data .... 79 

IV.C.5.b. Evaluation of the Estimated kpH Data ...... 82 

IV . C. 6 . Nitroalkanes . . . . . . . . . . . . . . . . . . 82 

IV.C.6.a. Evaluation of the Experimental kOH Data .... 82 

IV.C.6.b. Evaluation of the Estimated kOH Data ...... 85 

IV. C. 7 . Alkyl Nitrites . . . . . . . . . . . . . . . . . 87 

IV.C.7.a. Evaluation of the Experimental kpH Data .... 87 

IV.C.7.b. Evaluation of the Estimated kOH Data ...... 88 

IV.D. Addition of Hydroxyl Radicals to Alkenes, 

Conjugated Dialkenes, Alkynes, and 

1, 2-Dialkenes . . . . . . . . . . . . . . . . . 89 

IV.D.1. Unsubstituted Alkenes . . . . . . . . . . . . . 89 

IV.D.i.a. Evaluation of the Experimental kOH Data .... 89 

IV.D.l.b. Evaluation of the Estimated kp HData ...... 93 

IV.D.2. Substituted Alkenes . . . . . . . . . . . . . . 94 

IV.D.2.a. Evaluation of the Experimental k OH Data .... 94 

IV.D.2.b. Evaluation of the Estimated k OH Data ...... 97 

IV.D.3. Conjugated Dienes . . . . . . . . . . . . . . . 97 

IV.D.3.a Evaluation of the Experimental k OH Data .... 97 

IV.D.3.b. Evaluation of the Estimated k OHData. ..... 99 

IV.D.4. Alkynes and 1,2-Dienes (Allenes) . . . . . . . . 99 

IV.D.4.a. Evaluation of the Experimental k OH Data .... 99 

IV.D.4.b. Evaluation of the Estimated k OH Data ..... 99 

t 

iii 
, 

IV.E. Reaction of Hydroxyl Radicals with Organic 

Compounds Containing Sulfur, Nitrogen, and 

Phosphorous Functional Groups . . . . . . . . . 101 

IV.E.1. Reaction with Thiols, Sulfides, and Disulfides . 101 

IV.E.i.a. Evaluation of the Experimental kOHData .... 101 

IV.E.i.b. Evaluation of the Estimated kpH Data ...... 104 

IV.E.2. Reaction with Sulfoxides and Sulfates ..... 105 

IV.E.2.a. Evaluation of the Experimental kOH Data .... 105 

IV.E.2.b. Evaluation of the Estimated kOH Data ..... 105 

IV.E.3. Reaction with Alkyl Amines, Alkyl Hydrazines, 

and N-Substituted Amines . . . . . . . . . . . . 108 

IV.E.3.a. Evaluaticn of the Experimental kpH Data .... 108 

IV.E.3.b. Evaluation of the Estimated kOH Data ...... 108 

IV.E.4. Reaction with Compounds Containing Phosphorous 

Functional Groups . . . . . . . . . . . . . . . 110 

IV.E.4.a. Evaluation of the Experimental kOH Data .... 110 

IV.E.4.b. Evaluation of the Estimated kOH Data ...... 110 

IV.F. Reaction of Hydroxyl Radicals with Aromatic 

Compounds, Heterocyclic Aromatic Compounds, 

and Fused Ring Polyaromatic Compounds ..... 113 

IV.F.1. Aromatic Compounds . . . . . . . . . . . . . . . 113 

IV.F.i.a. Evaluation of the Experimental kpH Data .... 113 

IV.F.i.b. Evaluation of the Estimated Data ........ 119 

IV.F.2. Heterocyclic Aromatic Compounds . . . . . . . . 120 

IV.F.2.a. Evaluation of the Experimental kOH Data .... 120 

IV.F.2.b. Evaluation of the Estimated kOH Data ...... 122 

IV.F.3. Fused Ring Polyaromatic Compounds ....... 123 

IV.F.3.a. Evaluation of the Experimental kOH Data .... 123 

IV.F.3.b. Evaluation of the Estimated kOH Data ...... 123 

iv 
IV.G. Evaluation of the Estimated Half-Life for 

the Reaction of Hydroxyl Radicals with 

Organic Chemicals in the Troposphere ...... 125 

V. References . . . . . . . . . . . . . . . . . . . 127 

v 
i 

LIST OF TABLES 

Table 1. Group Rate Constants for Hydrogen Abstraction 

and Radical Reaction . . . . . . . . . . . . . 30 

Table 2. Substituent F(X) Factors for Hydrogen 

Abstraction . . . . . . . . . . . . . . . . . 31 

Table 3. Factors Used for Aliphatic Ring Strain 

Ef f ects . . . . . . . . . . . . . . . . . . . 33 

Table 4. Group Rate Constants for OH Radical Addition 

to Isolated Olefinic Units . . . . . . . . . . 34 

Table 5. Group Rate Constants for OH Radical Addition 

to Conjugated Olefinic Units . . . . . . . . . 35 

Table 6. Group Rate Constants for OH Radical Addition 

to Alkyne Units . . . . . . . . . . . . . . . 37 

Table 7. Group Rate Constants for OH Radical Addition 

to 1,2-Dialkene (Allene) Units . . . . . . . . 38 

Table 8. Substituent Factors CC(X)] for OH Radical 

Addition to Olefins and Acetylenes ...... 39 

Table 9. Electrophilic Substituent Factors for OH 

Radical Addition to Aromatic Rings ...... 40 

Table 10. Experimental Values of Ai for Some 

Monocyclic Heteroaromatic Compounds . . . . . 47 

Table 11. Experimental Values of Bi for Some 

Polynuclear Aromatic Compounds . . . . . . . 48 

Table 12. Values of Bi for Polynuclear Aromatic 

Hydrocarbon Structures Derived from 

Experimentally Measured Ionization 

Potentials . . . . . . . . . . . . . . . . . . 49 

Table 13. Values of Bi for Polynuclear Heteroaromatic 

Structures Derived from Experimentally Measured 

Ionization Potentials . . . . . . . . . . . . 50 

Table 14.A. Comparison of the Estimated Values of 

k~H at 298 K for Saturated Acyclic 

A kanes from the Atmospheric Oxidation 

Computer Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data 

Reported in AOP . . . . . . . . . . . . . . . 53 

vi 
Table 14.B. Comparison of the Estimated Values of 

kOH at 298 K for Saturated Cyclic 

Alkanes from the Atmospheric Oxidation 

Computer Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data 

Reported in AOP . . . . . . . . . . . . . . . . 55 

Table 15. Comparison of the Estimated Values of 

kOH at 298 K for Haloalkanes from the 

Atmospheric Oxidation Computer Program 

(AOP) and from a Hand Calculation (HC) 

and the Experimental kOH Data Reported 

in the Literature Versus the Experimental 

kOH Data in AOP . . . . . . . . . . . . . . . . 60 

Table 16. Comparison of the Estimated Values of 

kOH at 298 K for Carbonyl Compounds 

from the Atmospheric Oxidation Computer 

Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOg Data in 

AOP . . . . . . . . . . . . . . . . . . . . . . 63 

Table 17. Comparison of the Estimated Values of 

kOHat 298 K for Alcohols, Glycols, 

Ethers, and Hydroperoxides from the 

Atmospheric Oxidation Computer Program 

(AOP) and from a Hand Calculation (HC) 

and the Experimental k OHData Reported 

in the Literature Versus the 

Experimental kOHData in AOP . . . . . . . . . 72 

Table 18. Comparison of the Estimated Values of 

kpH at 298 K for Alkyl Nitrates and 

Alkyl Nitriles from the Atmospheric 

Oxidation Computer Program (AOP) and 

from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the 

Literature Versus the Experimental 

kOH Data in AOP . . . . . . . . . . . . . . . . 80 

Table 19. Comparison of the Estimated Values of 

koH at 298 K for Nitroalkanes and 

Alkyl Nitrites from the Atmospheric 

Oxidation Computer Program (AOP) and 

from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the 

Literature Versus the Experiment kOH 

Data in AOP . . . . . . . . . . . . . . . . . . 83 

_ 

vii 
. q 

Table 20. Comparison of the Estimated Values of 

kOH at 298 K for Unsubstituted Alkenes 

from the Atmospheric Oxidation Computer 

Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data in 

AOP. . . . . . . . . . . . . . . . . . . . . . 90 

Table 21. Comparison of the Estimated Values of 

k0H at 298 K for Substituted Alkenes 

from the Atmospheric Oxidation Computer 

Program (AOP) and From a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data in 

AOP . . . . . . . . . . . . . . . . . . . . . . 95 

Table 22. Comparison of the Estimated Values of 

kOH at 298 K for Conjugated Acyclic and 

Cyclic Dialkenes from the Atmospheric 

Oxidation Computer Program (AOP) and 

from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the 

Literature Versus the Experimental kOH 

Data in AOP . . . . . . . . . . . . . . . . . . 98 

Table 23. Comparison of the Estimated Values of 

kQH at 298 K for Alkynes and 1,2- 

Dialkenes (Allenes) from the 

Atmospheric Oxidation Computer Program 

(AOP) and from a Hand Calculation (HC) 

and the Experimental kOH Data Reported 

in the Literature Versus the 

Experimental kOH Data in AOP. . . . . . . . . . 100 

Table 24. Comparison of the Estimated Values of 

kOH at 298 K for Alkyl Thiols, 

Sulfides, and Disulfides from the 

Atmospheric Oxidation Computer Program 

(AOP) and from a Hand Calculation (HC) 

and the Experimental kOH Data Reported 

in the Literature Versus the 

Experimental kOH Data in AOP . . . . . . . . . 102 

viii 
f 

Table 25. Comparison of Estimated Values of kOH 

at 298 K for Alkyl Sulfoxides and 

Sulfates from the Atmospheric oxidation 

Computer Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOHData Reported in the Literature 

Versus the Experimental kOg Data in 

AOP . . . . . . . . . . . . . . . . . . . . . . 106 

Table 26. Comparison of the Estimated Values of 

k0H at 298 K for Alkyl Amines, 

Hydrazines, and N-Substituted Amines 

from the Atmospheric Oxidation Computer 

Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOHData Reported in the Literature 

Versus the Experimental kOHData in 

AOP. . . . . . . . . . . . . . . . . . . . . . 109 

Table 27. Comparison of the Estimated Values of 

kOH at 298 K for Aliphatic Compounds 

Containing Phosphorous Functional 

Groups from the Atmospheric Oxidation 

Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data in 

AOP. . . . . . . . . . . . . . . . . . . . . . 111 

Table 28. Comparison of the Estimated Values of 

kOH at 298 K for Aromatic Compounds 

from the Atmospheric Oxidation 

Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental kOH Data in 

AOP. . . . . . . . . . . . . . . . . . . . . 114 

Table 29. Comparison of the Estimated Values of 

kOH at 298 K for Heterocyclic Aromatic 

Compounds from the Atmospheric 

Oxidation Program (AOP) and from a Hand 

Calculation (HC) and the Experimental 

kOH Data Reported in the Literature 

Versus the Experimental k OH Data in 

AOP . . . . . . . . . . . . . . . . . . . . . . 121 

ix 
i 

Table 30. Comparison of the Estimated Values of 

k0H at 298 K for Fused Ring 

Polyaromatic Compounds (PAH) from the 

Atmospheric Oxidation Program (AOP) and 

from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the 

Literature Versus the Experimental kOH 

Data in AOP . . . . . . . . . . . . . . . . . . 124 

x 
LIST OF FIGURES 

Figure 1. Atmospheric Oxidation Program Data 

Entry Display . . . . . . . . . . . . . . . . . 16 

Figure 2. Atmospheric Oxidation Program Data Display 

for the Compound ac-Methyl Styrene (2-Phenyl1-Propene): 

Summary Hydroxyl Radical Data and Experimental 

Data. 

A. Screen Display when Key PgDn is pressed. .. 18 

B. Screen Display when Key F-10 is pressed. .. 19 

Figure 3. Atmospheric Oxidation Program Data Display 

for the Compound ac-Methyl Styrene (2-Phenyl1-Propene): 

Summary Hydroxyl Radical and Ozone Data. 

A. Screen Display when Key PgDn is pressed. .. 22 

B. Screen Display when Key F-10 is pressed. .. 23 

Figure 4. Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene (2-Phenyl1-Propene): 

A. Screen Display of the Detailed Calculations 

for Hydrogen Abstraction. . . . . . . . 24 

B. Screen Display of the Detailed Calculations 

for OH Radical Addition to the Olef inic 

Bond . . . . . . . . . . . . . . . . . . . . 25 

Figure 5. Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene (2-Phenyl1-Propene): 

A. Screen Display of the Detailed 

Calculations with 0 3Reaction with the 

Olefinic Bond. . . .. . . . . . . . . . 26 

B. Screen Display of the Detailed 

Calculations of OH Radical Addition to the 

Aromatic Ring . . . . . . . . . . . . . . . . 27 

Figure 6. Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene (2-Phenyl1-Propene): 

Screen Display for OH Addition to the 

Aromatic Ring and the Experimental Data. .... 28 

: 

xi 
a 

Abstract 

Atkinson (of the University of California at Riverside), in 

support of the research programs of the Exposure Assessment 

Branch, Office of Pollution Prevention and Toxics, U.S. 

Environmental Protection Agency, developed structure/reactivity 

relationships (S/R) for estimating the second-order rate constant 

for the reaction of hydroxyl radicals with organic chemicals in 

the gas-phase in the troposphere (kOH). Meylan, of Syracuse 

Research Corporation, computerized these S/R relationships and, 

in addition, developed S/R relationships for a few other classes 

of organic chemicals. This computer program is called the 

Atmospheric Oxidation Program (AOP) 1 . Furthermore, at the 

request of Leifer, Meylan incorporated a data base of the 

experimental values of kOg for a large number of organic 

chemicals in AOPI . 

This computer program is operated by inserting in it the 

SMILES notation for a given molecular structure. This SMILES 

notation is a machine-readable code for the molecular structure 

of an organic chemical. AOP then estimates kOH, lists an 

experimental value (if available from the scientific literature), 

t This computer program also contains S/R relationships of 

Atkinson for estimating the second-order rate constant for the 

reaction of organic chemicals with ozone (k 0 ) in the gasphase in the troposphere. This report, howe4er, will only 

review the hydroxyl radical portion of this computer program. 

2 AOP also lists the experimental values of k03 , if available; 

and also lists the experimental values of kN 0 for the reaction 

of an organic chemical with nitrate radicals NO3), if 

available. 

xii 
: 

gives a detailed description of the calculations, and estimates 

the half-life in the troposphere for this chemical. This 

computer program was thoroughly evaluated by comparing the 

estimated and experimental values of kO Hfrom AOP with the hand 

calculated and experimental values of Leifer for 454 organic 

compounds covering a wide variety of classes of compounds. These 

koHdata are listed in Tables 14-30. 

When comparing the estimated values of kOH by AOP and those 

by Leifer in a hand calculation (HC), a few comments can be made 

about the number of significant figures used. In general, the 

summary table in AOP lists k(i) and kOH (the rate constant 

corresponding to each individual reaction pathway i and the total 

hydroxyl radical rate constant kOH, respectively) with up to a 

maximum of six significant figures. However, the group rate 

constants (e.g., kP, ks, kt, koks , oko , (>N-), k(-SH), etc.) and 

the substituent factors F(i) and C(i) [e.g., F(-CH 2 -), F(-C1), 

F(>N-H), F(for strained rings containing n atoms), C(-F), C(=0), 

C(-CnN), etc.] are known, at best, to three significant figures 

and, in general, to two significant figures. Therefore, it is 

recommended that AOP show the detailed calculations to four 

significant figures and list k(la), k(ic), k(>N-), kadd,nar, 

kadd,ar, etc. and kOH in the summary table with three significant 

figures. 

In general, after evaluating all 454 chemicals covering a 

wide range of chemical classes, it was found that there was 

excellent agreement between the estimated values of kOH and HC. 

xiii 
, 

Furthermore, the S/R relationships of Meylan for fused ring 

polyaromatic hydrocarbons are superior to those of Atkinson. In 

addition, Meylan's S/R relationships have been expanded to cover 

heterocyclic aromatic compounds such as the thiazoles, oxazoles, 

pyridines, furans, etc. whereas Atkinson does not have 

corresponding S/R relationships. However, it must be emphasized 

that considerably more experimental kOH data are needed for a 

number of substituted heterocyclic and fused ring polynuclear 

aromatic hydrocarbons to verify the S/R relationships of Meylan. 

There are, however, some differences between the estimated values 

of kOH from AOP and HC for a few classes of compounds which will 

be described in the following paragraphs. 

For the alkyl sulfides (both acyclic and cyclic), a 

comparison of the estimated values of kOH from AOP and HC 

indicates that kOH is larger from AOP. The reason for this 

discrepancy is that kOH was measured in the absence of oxygen and 

from Atkinson's S/R relationships, k(-S-) = 0 so that only H-atom 

abstraction is observed. However, AOP estimates kOH by assuming 

that k(-S-) = 2.0 and not 0. Hence, when estimating k OHfor 

these compounds it is necessary to specify whether the estimation 

is made under the boundary condition of the presence or absence 

of oxygen. Therefore, it is recommended that AOP should be 

modified to take into account this boundary condition. 

For the aromatic compounds 3,5-dimethyl phenol, N,Ndimethylaniline, and 2,4-toluenediamine, AOP lists the maximum 

value for OH addition to an aromatic ring as 200 x 10 -12 

xiv 
i 

s 

s 

cm3 molecule- is -1[i.e., k(7) = kadd,ar] Wherea.s HC lists a 

maximum value kOHof 200 x 10-12 cm3 molecule-I S"1 . Since the 

maximum allowed collision rate is 200 x 10 -12 cm3 molecule- is -1 

[Atkinson (1987)], this boundary condition must be invoked on the 

estimation of kOH and not on k(7)[=kadd,arl• Furthermore, by 

using this boundary condition, the estimated values of k OHfor 

the above mentioned aromatic compounds are much closer to the 

experimental values [See Table 28 of this report and Leifer 

(1992a)]. It should be noted that this comment is only 

applicable to aromatic compounds and not to all compounds. 

For the compounds tetralin, indan, fluorene, and 

2,3-dihydrobenzofuran, AOP makes a slight error in estimating the 

rate constant for the addition of OH radicals to the aromatic 

ring [i.e., k(7) = kadd,ar]• For these compounds, AOP uses the 

incorrect value of vm(-CH2-) = 0.06 ** instead of the correct 

value of 0.064 **. Furthermore, the compounds tetralin, indan, 

and fluorene contain five membered strained rings. In 

calculating k(ic) for these compounds, AOP makes an error by 

omitting the ring strain factor F(5) = 0.80. Thus, k(ic) and kOH 

are erroneous. 

Atkinson did not develop S/R relationships for alkyl 

carboxylic acids, peroxides, sulfoxides, and sulfates because of 

the very limited availability of experimental kOHdata. Meylan 

did develop S/R relationships for these classes of compounds; 

however, for a few reasons, these S/R relationships are not 

valid. For the alkyl carboxylic acids and hydroperoxides, 

xv 
i 

a 

Meylan made an erroneous assumption about the mechanism of OH 

reaction for these compounds. For example, for the S/R 

relationships of the alkyl carboxylic acids, Meylan assumed that 

OH radicals can react with these compounds by H-atom abstraction 

from the hydroxyl group in the carboxylic acid group {C(=0)OH, 

[k(2))} and from the C-H groups in the alkyl group [k(la)] and 

that the dominant reaction pathway was H-atom abstraction from 

the alkyl group. As a result, Meylan assumed that k(-OH) = 

0.036, the same value as assigned to H-atom abstraction from the 

hydroxyl group in alcohols and glycols. However, based on the 

analysis of the experimental data of Wine et al. (1986) and 

Singleton et al. (1986), Atkinson (1989) and Leifer concluded 

that the major reaction pathway was H-atom abstraction from the 

hydroxyl group and k(-OH) > k(la). Therefore, it is recommended 

that the S/R relationships for the alkyl carboxylic acids and 

hydroperoxides be deleted from AOP. More experimental k OHdata 

are needed for additional alkyl carboxylic acids and 

hydroperoxides to develop reliable S/R relationships. 

For the alkyl sulfoxides, Meylan developed S/R 

relationships by assuming that only C-H abstraction from the 

alkyl groups occurred. However, intuitively, it is expected 

that the sulfoxide group would undergo further oxidation to the 

sulfone. Therefore, considerably more experimental kOH data are 

needed for additional sulfoxides before reliable mechanisms and 

S/R relations are developed; and these S/R relationships should 

be deleted from AOP. 

xvi 
: 

~ 

Based on the very limited data of the alkyl sulfates (only 

dimethyl and diethyl sulfate), Meylan developed S/R relationships for this class of compounds. Comparison of the estimated 

kpg data with the experimental kOH indicated that dimethyl 

sulfate gave an error of >+250$ and diethyl sulfate gave an 

error of +540$. These results are very poor so that it is 

recommended that these S/R relationships be deleted from AOP 

until considerably more experimental kOH data is available for 

additional sulfates to develop reliable S/R relationships. 

Meylan, in AOP, used the S/R relationships of Atkinson for 

the nitroalkanes based on the available experimental k OHdata 

for these compounds. However, it must be emphasized that some 

of the experimental data is suspect because nitroalkanes are 

very labile to direct photolysis and it is not clear whether 

photolysis occurred under the experimental conditions of the 

relative rate study of Nielson et al. (1988) or whether 

photolysis was taken into account. Therefore, it is recommended 

that AOP delete these S/R relationships. More reliable experimental kOH data are needed for these nitroalkanes under 

carefully controlled experimental conditions to eliminate, or 

account for, direct photolysis in order to develop more reliable 

S/R relationships. 

Comparison of the experimental values of kpH from AOP and 

Leifer for 454 chemicals indicates that, in general, the 

agreement is excellent. There are, however, a few differences. 

The primary difference is related to the number of significant 

4 

f 

xvii 
".. 

® 

figures used in AOP. For example, for 2-methylpentane, AOP 

lists an experimental value of 5.60 while Atkinson (1989) and 

Leifer (1992a) list a recommended value of 5.6; for 2,3- 

dimethyl-2-butene, AOP lists a value of 110.0 while the 

recommended value by Atkinson and Leifer is 110; for dimethylhydroxylamine, AOP lists a value of 90.0 while Atkinson and 

Leifer recommend a value of 90; for p-cresol, AOP lists a value 

of 47.0 while Atkinson and Leifer recommend a value of 47; for 

4-chlorobiphenyl, AOP lists a value of 3.9 while Atkinson and 

Leifer list a value of 3.86. 

For other chemicals with differences, Leifer lists an 

average value from the literature while AOP selects one set. 

For example, for ns-1,4-hexadiene, Leifer lists an average 

value of 90.6 from two sets of experimental data while AOP 

selects only one value, namely 90.3; for 2,3-dimethyl-2-pentene, 

AOP selects one value which is 108.0 while Leifer cites an 

average value of 103 based on both sets of experimental data. 

Unless there is good reason for discarding specific sets of 

experimental kOH data, it is better to use an average value from 

both sets. 

For 12 chemicals, AOP does not list experimental values: 

for example, four ketenes; 0 3 -carene;g&Q-butyl acetate; and 2- 

(chloromethyl)-3-chloro-i-propene. Differences were observed 

for a few compounds: e.g., for methane, AOP lists a value of 

0.00841 while Atkinson and Leifer list a recommended value of 

0.00836; for 2-octanone, AOP lists a value of 10.0 while 

xviii 
_ ~ 

Atkinson and Leifer list a value of 11.0; for 1,1,1-trifluoroethane, AOP lists a value of 0.017 while Atkinson and Leifer 

list a value of 0.0017. 

xix 
•`- 

~ 

I. Introduction 

Numerous chemicals, both natural and anthropogenic, are 

emitted to the troposphere from a variety of sources and may be 

removed by wet or dry deposition or by three important 

transformation processes. These three transformation processes 

are: 

(1) direct photoreaction which involves the absorption of 

sunlight followed by transformation; 

(2) indirect photoreaction which involves the reaction of a 

chemical with hydroxyl radicals (OH); and 

(3) oxidation which involves the reaction of a chemical 

with ozone (03). 

There is another indirect photoreaction process which involves 

the reaction of a chemical with nitrate radicals (NO 3 ) during the 

night. However, this transformation process only occurs for a 

few types of chemicals (e.g., olefins, phenols, and cresols); 

hence, it will not be considered when determining the rate of 

transformation in the troposphere. 

A quantitative measure of the three important 

transformation processes is given by the rate constants kdE, 

kOH, and k0 

3

. The rate constant kdE represents the first-order 

rate constant for direct photoreaction, while k Og and k0 

3 

represent second-order rate constants for indirect photoreaction 

and oxidation with OH and 0 3 , respectively. 

-1- 
a 

t 

The first report in a series titled "DETERMINATION OF RATES 

OF REACTION IN THE GAS-PHASE IN THE TROPOSPHERE. THEORY AND 

PRACTICE" describes a hierarchal test scheme for determining the 

rate constants kdE ,kOH, and k03 and the half-lives [t(1/2)E] 

for each transformation process and the net half-life in the 

troposphere [Leifer (1989a)]. The second report describes a 

screening-level test guideline for determining the maximum rate 

of direct photoreaction [kdE]max and the minimum half-life 

[t(1/2)E]min by the use of Ultraviolet-Visible Absorption 

Spectroscopy [Leifer (1989b)]. 

The third and fourth reports in this series describe 

structure/reactivity (S/R) relationships for estimating kOg for 

the reaction of an organic chemical with hydroxyl radicals in 

the gas-phase in the troposphere. These methods were developed 

by Atkinson (1986, 1986a, 1987, 1987a, 1988) for the Exposure 

Assessment Branch of the Office of Pollution Prevention and 

Toxics, U.S. Environmental Protection Agency. Report No. 4 

[Leifer (1992b)] represents a test guideline [§796.3900] for 

use in sections 4 and 5 of the Toxic Substances Control Act; 

report No. 3[Leifer (1992a)] represents the technical support 

document for this test guideline. 

Since these S/R relationships are excellent [Leifer 

(1992a)], they have been computerized by Syracuse Research 

Corporation [Meylan (1990a, 1990b)]. At the suggestion of 

Leifer, Syracuse incorporated a data base in this computer 

program which lists the experimental values of kOg as reported 

: 

a 

-2- 
s 

r 

` 

in the literature [Meylan (1990b)]. This document, describes an 

assessment of this computer program for estimating kOg and 

represents report No.5 in this series. 

II. Mathematical Synopsis of the Structure/Reactivity 

Relationships of Atkinson and Meylan 

Atkinson (1986, 1986a, 1987, 1987b, 1988, 1988a) critically 

analyaed the hydroxyl radical rate data (kOH) for a large number 

of organic chemicals and developed a number of S/R relationships 

based solely on the molecular structure of these .chemicals. In 

developing these S/R relationships, he assumed that a number of 

OH radical reaction pathways exist and the various OH radical 

reaction pathways could be separated and treated individually. 

Therefore, he calculated rate constants for each of these 

reaction pathways. The reaction pathways and rate constants for 

each of these pathways were: 

rsunsaturated

-atom abstraction from acyclic 

k(1) = k aturated, cyclic saturated, and 

 C-H groups by OH radicals 

CH-atom abstraction from 0-H groups ~ k(2) = k by OH radicals (2) 

r~>,C=C-O

H radical addition to >C=C<,

k(3) = k C=C-C=C<, -CNC-, and >C=C=C<, (3) 

 groups 

k(4)= k r_S-,

H radical interaction with -SH, (4) 

 and -S-S- groups 

OH radical interaction with -NH2, k(5)= k I>NH, and >N- groups (5) 

-3- 
s 

~ 

~hosphorus

H radical interaction with k(6) = k groups , (6) 

k(7) = k[OH radical addition to aromatic rings] (7) 

LP

OH radical addition to fused ring

k(8) = k olyaromatic compounds (i.e., (8) 

olyaromatic hydrocarbons) 

Atkinson postulated that the overall OH radical rate constant kOH 

is equal to the sum of the rate constants for each of these 

reaction pathways. Therefore, the OH radical rate constant is 

given by the equation 

8 ka, _ ~' k ( i ) ( 9 ) 

and the individual rate constants [k(1), k(2), •••••, k(8)] and 

kOH are all in the units cm 3 molecule- is-1 . Structure/ 

reactivity relationships will be described for each of these 

reaction pathways. 

Path av 1: H-atom abstraction from acyclic and cyclic 

saturated and unsaturated C-H groups by OH 

radicals 

The overall rate constant for reaction pathway 1 is given 

by the equation 

k(1) = k(la) + k(lc) + k(1, UNS CH) (10) 

where k(la) represents the rate constant for H-atom abstraction 

from all acyclic saturated C-H groups by OH radicals at 298 K; 

: 

~ 

-4- 
E_ 

♦ 

a_ 

k(lc) represents the rate constant for H-atom abstraction from 

all cyclic saturated C-H groups by OH radicals at 298 K; and 

k(1, UNS CH) represents the rate constant for H-atom abstraction 

from all unsaturated C-H groups (e.g.,=C-H) by OH radicals at 

298 K. 

The rate constant k(la) is given by the mathematical 

relationship 

k(1a)= r)kpFi (X) +,) ksF j(X ) F j(Y) 

iZ~ (11) 

± ~riktFm (X)Fm (Y)Fm (Z) 

k(ic)_ (,~) ksF~ (X)F ~ (Y) + m~ ktFm (X)Fm (Y)Fm (Z)1 F(n) (12) 

k(1, UNS CH) = 0 (13) 

where kP, ks, kt represent the group rate constants for primary 

(CH3-), secondary (>CH2), and tertiary (>CH-) groups, 

respectively, and the values for these parameters at 298 K are 

listed in Table 1 of an EPA report by Leifer (1992a), in Table 1 

of a report by Meylan (1990b) 3 , and in Table 1, Section IV, of 

this report; r , ~ , ~ , X , , represent the 

 m c) 

summation over all primary acyclic, secondary acyclic, tertiary 

acyclic, secondary and tertiary cyclic groups, respectively, in 

3Group Rate Constants and Substituent Values Used by the 

Atmospheric Oxidation Program, Version 1.30, November 1, 

1990. 

-5- 
the molecule; F(X), F(Y), F(Z) represent the substituent factors 

for substituents X, Y, and Z and the values for various 

substituents at 298 K are listed in Table 2 of an EPA report by 

Leifer (1992a), in Table 6 of a report by Meylan 

(1990b) 3 , and in Table 2, Section IV, of this report; F(n) 

represents the ring strain factor for saturated and unsaturated 

rings and heterocyclic rings containing n(3,4,5) atoms at 298 K 

and the values are listed in Table 2 of an EPA report by Leifer 

(1992a), in Table 10 of a report by Meylan (1990b) 3 , and in 

Table 3, Section IV, of this report. For rings with n(6,7,8, 

etc.), with essentially no ring strain, F(n) = 1.0 at 298 K. 

Pathway 2: H-Atom abstraction from -O-H groups in alcohols and 

glycols by OH radicals 

The overall rate constant for reaction pathway 2 is given 

by the equation 

k(2) = n(-O-H) k(-OH) (14) 

where n(-O-H) represents the number of hydroxyl groups (-O-H) in 

the molecule; k(-OH) represents the group rate constant for Hatom abstraction from the hydroxyl group in alcohols and glycols 

and is equal to 0.036 x 10 -12 cm3molecule- ls-1at 298 K[Table 1 

of an EPA report by Leifer (1992a), in Table 1 of a report by 

Meylan (1990b) 3 , and in Table 1, Section IV, of this report). 

r 

: 

mc 
e 

w 

s 

~ 

Pathwav 3 : OH radical addition to isolated alkene groups 

(>C=C<), nonaromatic conjugated groups 

(>C=C-C=C<), and other unsaturated groups 

(-CNC-, >C=C=C<, >C=C=O) 

The overall rate constant for reaction pathway 3 is given 

by the equation 

k(3) = kadd,nar 

= rkosCi (X) Ci (Y) + Ekao Cj (X) Cj (Y) + 

T (15) 

+ ~ kouCm(X)Cm(Y) 

■ 

where kos, koo, kau represent the group rate constants for OH 

radical addition (add) to isolated (is) carbon-carbon double 

bonds, nonaromatic (nar) conjugated (co) carbon-carbon bond 

systems, and other unsaturated (ou) carbon-carbon systems, 

respectively, and the values of these group rate constants at 

298 K are given in Tables 9, 11, and 12, respectively, of an EPA 

report by Leifer (1992a), in Tables 2, 5, (3 and 4), 

respectively, of a report by Meylan (1990b) 3 , and in Tables 4, 

5, (6 and 7), respectively, Section IV, of this report; F, F, 

, J 

represent the summation over all isolated carbon-carbon 

■ 

double bond systems, nonaromatic conjugated carbon-carbon double 

bond systems, and other unsaturated carbon-carbon groups, 

respectively, in the molecule; C(X) and C(Y) represent the 

substituent factors at 298 K for substituents X and Y and are 

listed in Table 10 of an EPA report by Leifer (1992a), in Table 

-7- 
7 of a report by Meylan (1990b) 3 , and in Table 8, Section IV, of 

this report. 

Pathway 4: OH radical interaction with -SH, -S-, and -S-Sgroups 

The overall rate constant for reaction pathway 4 is given 

by the equation 

k(4) = n(-SH)k(-SH) + n(-S-)k(-S-) + n(-S-S-)k(-S-S-) (16) 

where n(-SH), n(-S-), and n(-S-S-) represent the number of -SH, 

-S-, and -S-S- groups, respectively, in the molecule; k(-SH), 

k(-S-), k(-S-S-) represent the group rate constants for OH 

radical interaction with the -SH, -S-, and -S-S- groups, 

respectively, and the values of these group rate constants at 

298 K are listed in Table 1 of an EPA report by Leifer (1992a), 

in Table 1 of a report by Meylan (1990b) 3 , and in Table 1, 

Section IV, of this report. 

Pathway 5 : OH radical interaction with -NH2, >NH, and >Ngroups 

The overall rate constant for reaction pathway 5 is given 

by the equation 

k(5) = n(-NH2)k(-NH2) + n(>NH)k(>NH) + n(>N-)k(>N-) (17) 

where n(-NH2), n(>NH), n(>N-) represent the number of -NH2, >NH, 

and >N- groups, respectively, in the molecule; k(-NH2), k(>NH), 

k(>N-) represent the group rate constants for -NH2, >NH, and 

>N-, respectively, and the values of these group rate constants 

x _ 

~ _ 

-8- 
c 

~ 

~ 

at 298 K are listed in Table 1 of an EPA report by Leifer 

(1992a), in Table 1 of a report by Meylan (1990b) 3 , and in Table 

1, Section.IV, of this report. 

$athway 6: OH radical interaction with phosphorous groups 

The overall rate constant for reaction pathway 6 is given 

by the equation 

k(6) = n[>P(S)-]k[>P(S)-] + n[>P(0)-]k[>P(0)-] (18) 

+ n[>P(C1)<] k[>P(C1)<] 

where n[>P(S)-], n[>P(0)], n[>P(C1)<] represent the number of 

>P(S)-, >P(0)-, and >P(C1)< groups, respectively, in the 

molecule; k[>P(S)-], k[>P(0)-], k[>P(C1)<] represent the group 

rate constants for OH radical interaction with the >P(S)-, 

>P(0)-, and >P(C1)< groups, respectively, and the values of 

these group rate constants at 298 K are listed in Table 1 of an 

EPA report by Leifer (1992a), in Table 1 of a report by Meylan 

(1990b) 3 , and in Table 1, Section IV, of this report. 

Pathway 7 : OH radical addition to aromatic rings 

The overall rate constant k(7)[=kadd,ar] for reaction 

pathway 7 is given by the equation 

k(7) = k(7A) + k(7B) (19) 

where k(7A) corresponds to the addition of OH radicals to an 

aromatic ring (ar) and k(7B) corresponds to OH reaction with an 

heteroaromatic (monocyclic) ring (ar'). 

~s 
3 

~ 

For reaction of OH radicals with an aromatic ring 

k(7A) = kadd,ar (20) 

1og10k'add,ar - ~ ( 0.31 - 1.35 Min ( ,Eol ~ (21) 

kadd,ar - 10-12 kadd,ar (22) 

where ~ represents the summation over all aromatic rings in the 

molecule; (EQl ) represents the summation of the electrophilic 

substituent constants of Brown and Okamoto (1958) with respect to 

a given ring position (i.e., ortho, meta, para); and Min(QF ) ~ 

ol ) represents the summation of the electrophilic substituent 

constants with respect to the ring hydrogen position that gives 

the most negative summation value (i.e., Min ). Electrophilic 

substituent constants (Qm and Qp) for a number of substituents 

are given in Table 22 of an EPA report by Leifer (1992a), in 

Table 8 of a report by Meylan (1990b) 3 , and in Table 9, Section 

IV, of this report. 

Atkinson did not develop S/R relationships for OH radical 

addition to a heteroaromatic ring (monocyclic) while Meylan 

(1990b) 4 did develop S/R relationships. For OH radical addition 

to the heteroaromatic ring (arl), AOP uses the equation 

4User's Guide for the Atmospheric Oxidation Program, Version 

1.10, November 1, 1990. 

s 

-10- 
k(7B) = kadd,ar' (23) 

1og10kadd,ar' _ ~ tAi - 1.35 Min ( Eat ) ~ (24) 

e 

< 

s 

where ~ represents the 

~ 

Ai is a function of the 

basic, or parent, heteri 

cm3molecule-ls-1[Table 

page 7 of a document by 

summation over all heteroaromatic rings, 

experimental value of kadd,ar' of the 

Daromatic ring in the units 10-12 

10, Section IV, of this report and on 

Meylan (1990b) 4 ]; and the other 

parameters have been described previously. The use of equations 

23 and 24 will be discussed in more detail in Section IV.B. 

Pathway 8: OH radical addition to fused ring polyaromatic 

compounds 

The overall rate constant k(8) for reaction pathway 8 is 

given by the equation 

k(8) = k(8A) + k(8B) (25) 

where k(8A) corresponds to the addition of OH radicals to a 

polynuclear aromatic hydrocarbon ring (PAH) and k(8B) corresponds 

to the OH radical addition of OH radicals to a polynuclear 

heteroaromatic ring (PAH'). For OH addition to the polyaromatic 

hydrocarbon ring 

k(8A) = kadd,PAH (26) 

1og10k add,PAH = F,110.11 - 1.08 (IP)i - 1.35 Min( EQt ) ~ (27) 

-11- 
_ 

t 

kadd,PAH = 10-12k'add,PAH (28) 

where represents the summation of all PAHs, (IP)i represents 

~ - 

the ionization potential of the parent PAH in electron volts 

(eV) obtained from Weast (1976-1977); ( ~`Ql ) is derived for the 

4~

• 

monocyclic substituted portion of the molecule to allow for the 

effects of substituent groups on the reactivity and represents 

the summation of the electrophilic substituent constants of Brown 

and Okamoto (1958) with respect to a given ring position (i.e., 

ortho, meta, para); and Min( ~Q~ ) represents the summation of 

~ 

the electrophilic substituent constants with respect to the ring 

hydrogen position that gives the most negative summation (i.e., 

Min ). Electrophilic substituent constants (Qm and QP) for a 

number of substituents are given in Table 22 of an EPA report by 

Leifer (1992a), in Table 8 of a report by Meylan (1990b) 3 , and in 

Table 9, Section IV, of this report. 

For OH radical addition to fused polynuclear aromatic 

hydrocarbon rings, Meylan (1990b) 3 , developed a different 

approach to estimate kadd,PAH• Meylan, in AOP, uses the equation 

1og10kadd,PAH a ~ lBi - 1.35 del ~ (29) 

where ~ represents the summation over all fused polynuclear 

~ 

aromatic hydrocarbon rings, Bi is a function of the experimental 

value of kadd,pAH of the basic, or parent, polynuclear 

hydrocarbon aromatic ring in the units 10-12 cm3 molecule- is -1 

-12- 
L 

t 

L 

[Table il, Section IV, of this report and from Meylan (1990b) 4 

for naphthalene, anthracene, and phenanthrene] or is given an 

assigned value based primarily on the experimental ionization 

potential of the basic, or parent, polynuclear aromatic 

hydrocarbon ring in the units 10-12 cm3 molecule- ls-1 [Table 12, 

Section IV, of this report and from Meylan (1990b) 4 ] for 4, 5, 

and 6 fused benzene rings. The term det is related to the 

substituent factors cm and cP for various substituents and is 

determined in the following way. For monosubstituted PAH 

compounds, de# corresponds to the most negative value of Qm or aP 

for a given substituent on the ring. For polysubstituted PAH 

compounds, de~ corresponds to the sum of the average values of vm 

and cp for each substituent on both rings. 

For OH radical addition to polynuclear heteroaromatic rings 

(PAHI), Meylan (1990b) 4 uses a modified form of equation 29 which 

is 

1og10kadd,PAH' - Ir IB! - 1.35 det 1 (30) 

where Bi is now related to the experimental ionization potential 

of the basic, or parent, fused polynuclear heteroaromatic ring in 

the units 10-12cm3molecule- ls-1[obtained from Table 13, Section 

IV, of this report for a few fused polynuclear heteroaromatic 

rings and from Meylan (1990b) 4 ]. The term det is the same as the 

one described previously. It should be noted that at present, 

AOP cannot estimate kadd,PAH for fused ring structures contain- 

-13- 
ing five-membered heterocyclic rings. The use of equations 29 

and 30 will be discussed in more detail in Section IV.B. 

III. Syracuse Research Corporation Atmospheric Oxidation 

Computer Program (Developed by Meylan) 

III.A. Introduction 

The Atmospheric Oxidation Computer Program [designated as 

AOP] was purchased from Syracuse Research Corporation by the 

Exposure Assessment Branch of the Office of Pollution Prevention 

and Toxics, U.S. Environmental Protection Agency, based on the 

recommendation of Leifer. The first version, labeled Version 

1.00, was received July 10, 1990 [Meylan (1990a)]. The 

Atmospheric Oxidation Program estimates the second-order rate 

constant for the reaction of an organic chemical with hydroxyl 

radicals (kOH) and ozone (k03 ) in the gas-phase. These rate 

constants are then used to calculate the half-life [t(1/2)EJ for 

these two reaction pathways based on average hydroxyl radical and 

ozone concentrations in the troposphere. 

Based on a very preliminary evaluation of the hydroxyl 

radical portion of this program, a few errors were uncovered. 

After a discussion by phone with Meylan on August 2, 1990, 

changes were made in the hydroxyl radical portion of this 

program. The new AOP computer program, Version 1.30, was 

received on November 1, 1990 and contained a data base for 

experimental values for the reaction of organic chemicals with 

hydroxyl radicals (kOH), ozone (k03 ), and nitrate radicals 

(kNO3 ). This report covers the evaluation of the hydroxyl 

-14- 
_ 

radical portion of AOP. Future EPA reports will be devoted to 

the discussion of the S/R relationships of Atkinson and Carter 

(1984) for ozone and the evaluation of AOP for estimating k 03 and 

the corresponding half-life [t(1/2)El• 

III.B. Atmospheric Oxidation Computer Program (AOP) 

The estimation methods used in AOP are based on the 

structure/reactivity relationships of Atkinson (1986, 1986a, 

1987, 1987a, 1988, 1988a) for the gas-phase reaction of hydroxyl 

radicals with organic chemicals in the troposphere as described 

in detail in the report by Leifer (1992a) and the structure/ 

reactivity relationships of Atkinson and Carter (1984) for the 

gas-phase reaction of ozone with organic chemicals in the 

troposphere. As stated in Section III.A., only the AOP program 

for estimating kOH and t(1/2)E will be discussed in this report. 

AOP has been designed for use in an IBM or 

series of personal computers running the MS-DOS 

operating systems. Approximately 350 K of free 

required to run AOP. A11 program outputs occur 

and are run from a floppy disk drive. 

The AOP program is started by pressing key 

an IBM-compatible 

or PC-DOS 

memory are 

in the text mode 

F-8 of the 

Workstation Menu, typing in AOP, and then pressing the Enter key. 

Program execution begins by displaying the data input screen 

shown in Figure 1. The program version and date are displayed in 

the upper left corner of the screen. The present version is 

specified in three lines:Version:/SRC 1.30/Nov 1990. The large 

-15- 
. s 

Fiqure 1. Atmospheric Oxidation Proqram Data Entry Display 

V e r,s i. o n: I h1 h119 hl hl hl h1 hl M hl hl h119 h1 h119 M h1 1.111 M hl hl h1 !7 h1 hl h1 hl 1.119 J9 h1 h119 h1; 

SRC 1.3-0 , ATMOSF'HEE I C OX I DAT I ON F'ROr,EAM . 

Nov 1990 . F;ate of Hvdroxvl F;adical °< Dzone . 

, Feaction fr, om Chemical Structur, e , 

H h1 hl h1 !9 h1 h1 h1/? h1 h1 hl hl h1 h119 h1 M h1 hl h1 J11? hl h1 J91~1 h119 h1 hl h1/~1 h11919h1 ~' 

T hl hl h1 hl hl hl hl h1 h119 J419 hlhl hl h1 h119 hl hl hf h1 h1 J9 h1 hl hl hl hl h1 hl M h119 h1 J9 h1 h11919 hl hl M hl hl hl h1 h11919191919 hl hl/h1 M 1? h1 hl h1/9 f4/9 hl M hl hl hl M hl hl M h11? J9 1-119 : 

; r_ir7 0000r7 0000000000000r_'r000000t700000r7r7r.7r7r70r.j0000r'iri0r7000r7ra00xj000r700r70r7r7000000riri :ir.ir_'~ r? ~ 

: Enter, SMILES:O 000i 

; r i 0 r i 0 0 r i o o i i oo o o o o r'.i 0 r:! s 

s 0r7r_'rr ir_'arl00r i0r7 ri0r_'i0r70r_'r0000000r7000ri0000r70r7000000p00Q0r700r70000r_700000000rir.7r70000ri0r;7or.ic7 : 

. Enter,NAME : C) rir.;r:i> 

: 00ri0r70r70r7r7000000ri000r700Q0r7r7000r7p00000rir_70r_"10000r70ri00r7r7r70r_i00000000000U0000r7U0 ~:7r7r:r7.; 

H 19! 119 h1 h1 hl h1 h119 Mhl hl h1 h1 hl hl h119 J9 M h1 /9hl h1 1.1 h1 h1 h119 M h1191919 h1 J9 h1 h/ f9 hl h1 M hl f9 h1 h1 h1 h11h1 h11419 h119 h1191419 h1 h1 h1 hl !9 hl M J9 h1 !9 h1 h1 M M h1141919M M:` 

INS: OFF' 

LnDnnnnnnnnn.nnnnnnnnnnnn_nnnnnnnnnnnnnnnnnnnnnnDnnn_nnnnnnnn_nDnnnnnnnn.D_nnnDDDn.n.Dn: , 

3 Fi : CLEAR Input F6: Save l"nput to User Fi le PgDn: CAL_C! ~ LATE .3 

3 F2: F'hEVIi7US Input F8: CAS File Input Alt-H: SMILEc: ~. HELP 3 

3 F4: User,FILE InpL.it F10: CALC °< SAVE Results Esc: EXIT ta DCiS .j 

@nDnnnnDnnn _nnnnnnnDn _nnODnDnnl7nDDnnnnnDD _n _nnnnnnnnDnnnnnnnDDnn _nnnnnnnnnnD _n _nn _nnnDE»- 

-16- 
~ 

, 

rectangular box in the upper center of the screen contains the 

program name and purpose. A large box in the middle portion of 

the screen is used to enter the SMILES notation corresponding to 

the chemical to be used in the estimation. The SMILES notation 

is a computer readable molecular structure system. Currently, a 

maximum of 120 characters are allotted for the SMILES notation. 

Directly below the Enter SMILES box, is a box with Enter NAME. 

This box is used to enter the name of the chemical and a maximum 

of 60 characters are allotted for this purpose. The blank space 

in the lower portion of the screen is used to display error 

messages corresponding to the SMILES entry. Finally, the lower 

box contains the various edit keys. The reader is referred to 

the USERS GUIDE for AOP, Version 1.10, prepared by William Meylan 

of Syracuse Research Corporation, for a detailed discussion of 

the operation of AOP. 

The only data required for AOP to produce estimated and 

experimental values of kOH and t(1/2)E is the SMILES notation 

corresponding to the molecular structure of the chemical. The 

name of the chemical is optional and is not required to run AOP. 

As an illustration of the operation of AOP and the output data to 

the monitor screen, consider the chemical a-methyl styrene, 

(2-phenyl-l-propene) which has a SMILES notation C=C(C)cicccccl. 

This SMILES notation is entered at the point adjacent to the 

ENTER SMILES notation on the screen and pressing key PgDn. If 

the SMILES notation is correct, the data entry screen is removed 

and the kOg data are displayed on the screen, Figure 2.A. The 

-17- 
~ 

^^ 

Figure 2. Atmospheric Oxidation Program Data DispIay for the 

Compound a l Styrene (2-PhenyI-I-Properte): 

A. Screen Display when Key PgDn is pressed^ 

SMILES : C=C(C)c1ccccc1 

CHEM : 

MOL FOR: C9 H10 

MOL WT : 118.18 

SUMMARY: HYDROXYL RADlCALS 

Hydrogen Abstraction = .1440 E-12 cm3/molecule-sec 

Reaction with N, S and -OH = .0000 E-12 cm3/m01ecu1e-sec 

Addition to Triple Bonds = .0000 E-12 cm3/molecule-sec 

** Addition to Olefinic Bonds = 51.4000 E-12 cm3/molecule-sec 

** Addition to Aromatic Rings = 1.9187 E-12 cm3/molecule-sec 

Addition to Fused Rings = .0000 E-12 cm3/molecule-sec 

OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule-sec 

HALF-LIFE = .300 Days (at conc 5E5 yOH/cm3) 

........................ ** Designates Estimation(s) Using ASSUMED Value(s) 

ZDDDDDDDDDDDDBBDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

-----3 3-- 

OV3 Name: 2-Phenyl-1-propene (4-methyl styrene) 3 

HA3 CAS Number: 00098-83-9 3 

3 Exper OH rate constant : 52.0 E-12 cm3/molecule-sec 3 

3 Exper Ozone rate constant : --- cm3/molecule-sec 3 

3 Exper NO3 rate constant : --- cm3/molecule-sec 3 

3 3 

3 3 

@DDDDDDDDDDVDDDDDDD4 Press any key to continue... CDDDDDDDDDDDDDDDDDDDY 

, 

^^ 

-18- 
~ 

^` 

" 

~` 

B. Screeo DispIay nhen Key F-I0 is pressed. 

SMILES : C=C(C)c1ccccc1 IMHMHHHMMMMMMMMMMMMMHMx 

CHEM : : Summary Saved to: x 

MOL FOR: C9 H10 x file --> AOP1.DAT x 

MOL WT : 118.18 HHMHMMMHMHHHHMHHHHHHW< 

------------------------- SUMMARY: HYDROXYL RADICALS ------------------------- 

Hydrogen Abstraction = .1440 E-12 cm3/molecule-sec 

Reaction with N, S and -OH = .0000 E-12 cm3/molecule-sec 

Addition to Triple Bonds = .0000 E-12 cm3/molecule-sec 

** Addition to Olefinic Bonds = 51.4000 E-12 cm3/molecule-sec 

** Addition to Aromatic Rings = 1.9187 E-12 cm3/molecule-sec 

Addition to Fused Rings = .0000 E-12 cm3/molecule-sec 

OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule-sec 

HALF-LIFE = .300 Days (at conc 5E5 y0H/cm3> 

............~........... ** Designates Estimation(s) Using ASSUMED Value(s) 

ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

-----3 3-- 

OV3 Name: 2-Phenyl-1-propene 14-methyl styrene) 3 

HA3 CAS Number: 00098-83-9 3 

3 Exper OH rate constant : 52.0 E-12 cm3/molecule-sec 3 

3 Exper Ozone rate constant : --- cm3/molecule-sec 3 

3 Exper NO3 rate constant : --- cm3/molecule-sec 3 

3 3 

3 3 

@DDDDDDDDDDDDDDDDDD4 Press any key to continue... CDDDDDDDDDDDDDDDDDDDy 

-19- 
. L 

i 

; 1 

SMILES notation, molecular formula, and molecular viight of 

a-methyl styrene are displayed at the top left portion of the 

screen. Directly below these data and in the center of the 

screen, this figure displays the SUMMARY: HYDROXYL RADICALS data 

and the EXPERIMENTAL DATA. Directly under SUMMARY: HYDROXYL 

RADICALS, the estimated rate constants for each of the specific 

reaction pathways (ki) for a-methyl styrene are listed. 

Immediately below the summary data, the overall kOH rate constar* 

{which represents the sum of each of the individual rate 

constants [k(i)]} and the corresponding half-life are listed. 

The half-life (in days) corresponds to an average OH radical 

concentration of 5E5 radicals cm-3and a 24-hour daylight day. 

The table in the lower box summarizes the available 

experimental kOH, k03 , and kNO3 data for this compound. The 

experimental value of kOH is listed as 52.0 E-12 cm 3molecule- ls-1 

as obtained from Atkinson (1989). No experimental rate data are 

available for the reaction of a-methyl styrene with ozone (k03) 

and with nitrate radicals (kp0 3 ). If, after the SMILES notation 

for a-methyl styrene is entered, key F-10 is pressed instead of 

PgDn, the results are then displayed on the screen as shown in 

Figure 2.B. In this case, the estimated and experimental data 

are the same as the data in Figure 2.A. except that the estimated 

data are now stored in a file as indicated in the top right 

corner box. 

Pressing key PgDn displays the same OH rate data but now the 

SUMrIARY: OZONE REACTION data replaces the available experimental 

-20- 
~ 

a „ 

data, Figure 3A. The ozone data corresponds to the overall 

estimated ozone rate constant (k0 3 ) and the associated half-life 

[t(1/2)E] in days corresponding to an average ozone concentration 

of 7E11 molecules cm-3and a 24-hour day. If, after the SMILES 

notation for ac-methyl styrene is entered, key F-10 is pressed 

twice, then the results are depicted in Figure 3.B. In this 

case, the estimated data is the same as the data displayed in 

Figure 3.A. except that the data is now stored in a file as 

indicated in the box in the upper right corner. 

When pressing key F-9 five times, the screen displays 

sequentially for a-methyl styrene: 

(1) the detailed calculations for hydrogen abstraction 

[k(la)), Figure 4.A.; 

(2) OH addition to the olefinic group [k(3) = kadd,narl ► 

Figure 4.B.; 

(3) ozone reaction with the olefinic group, Figure 5.A.; 

(4) OH addition to the aromatic ring (ar) [k(7A) _ 

kadd,ar7, Figure 5.B; and 

(5) Figure 6, which corresponds to the same estimated data 

for OH addition to the aromatic ring (Figure 5.B.) and 

the experimental data in the lower box corresponds to 

the same experimental data displayed in Figure 2.A. 

If key F-9 is pressed again five times, the same sequence of 

data is displayed as described above. Pressing any key but F-9 

returns the screen display to Figure 1 for entry of a SMILES 

notation for another compound. If key F-2 is pressed, Figure 1 

-21- 
Figure 3. Atmospheric Oxidation Program Data DispIay for the 

Compound m-Methyl Styrene (2-PhenyI-I-Propeoe): 

A. Screen Display when Key PgDn is pressed, 

SMILES : C=C(C)c1ccccc1 

CHEM : 

MOL FOR: C9 H10 

MOL WT : 118.18 

------------------------- SUMMARY: HYDROXYL RADICALS ------------------------- 

Hydrogen Abstraction = .1440 E-12 cm3/molecule-sec 

Reaction with N, S and -OH = .0000 E-12 cm3/molecule-sec 

Addition to Trip1e Bonds = .0000 E-12 cm3/molecule-sec 

** Addition to Olefinic Bonds = 51.4000 E-12 cm3/molecule-sec 

** Addition to Aromatic Rings = 1.9187 E-12 cm3/molecule-sec 

Addition to Fused Rings = .0000 E-12 cm3/molecule-sec 

OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule-sec 

HALF-LIFE = .300 Days (at conc 5E5 y0H/cm3) 

.... ,................... ** Designates Estimation(s) Using ASSUMED Value(s) 

------------------------- SUMMARY: OZONE REACTION ---------------------------- 

OVERALL OZONE Rate Constant = 13.650000 E-17 cm3/molecule-sec 

HALF-LIFE = .084 Days (at conc 7E11 mol/cm3) 

Press F9 to Show Calc Press ESC to STOP....anything else to continue 
~ 

, 

^' 

SMILES : C=C(C)c1ccccc1 IMHHMMMMHHHMMMMMHMHMMW~ 

CHEM : : Summary Saved to: ~ 

MOL FOR: C9 H10 x fi}e --> A0P1.DAT ~ 

MOL WT : 118.18 HMHMHMMMMMMMMMMHMMMMMW 

------------------------- SUMMARY: HYDROXYL RADICALS ------------------------- 

Hydrogen Abstraction = .1440 E-12 cm3/molecule-sec 

Reaction with N v S and -OH = .0000 E-12 cm3/molecule"sec 

Addition to Triple Bonds = .0000 E-12 cm3/molecule-sec 

** Addition to Olefinic Bonds = 51.4000 E-12 cm3/molecule-sec 

** Addition to Aromatic Rings = 1.9187 E-12 cm3/molecule-sec 

Addition to Fused Rings = .0000 E-12 cm3/molecule-sec 

OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule-sec 

HALF-LIFE = .300 Days (at conc 5E5 yOH/cm3) 

........................ ** Designates Estimation(s) Using ASSUMED Value(s) 

------------------------- SUMMARY: OZONE REACTION ---------------------------- 

OVERALL OZONE Rate Constant = 13.650000 E-17 cm3/molecule-sec 

HALF-LIFE = .084 Days (at conc 7E11 mol/cm3) 

Press F9 to Show Calc Press ESC to STOP....anything else to continue 

-23- 
ra 

Figure 4. Atmospheric oxidation Program Data Display for the 

Compound a-Methyl Styrene (2-Phenyl-l-Propene): 

A. Screen Display of the Detailed Calculations for 

Hydrogen Abstraction. 

Hyd•oqen Abetractj.on 

[::'Prim = 0.144 F(:::-C=(-,::') = C.).144 ( = .144 

H Abstraction I- OTAL = .144 E•127' cm -1 /molecLt lo. ---sec - 

F'r- E-,ss arvy key tcj cont -Inue 

-24- 
~ 

°^ 

^^ 

B. Screen Display of the DetaiIed CalcuIations for 

OH Addition to Olefinic Bonds 

Kd = K(CH2=C<)C(-Pheny1 **) 

= 51.400(1.00) = 51.400 E-12 cm3/molecule-sec 

..,...~.................... ASSUMED Value designated by: ** 

Press any key to continue 

-25- 
Figure 5. Atmospheric Oxidation Program Data Display for the 

Compound a-Methyl Styrene (2-Phenyl-l-Propene): 

Ficrure 5 

A. screen Display of the Detailed Calculations with 

03 Reaction with the Olefinic Bond. 

Ozorie R'eAct:L0n with Olefins 

I -j T5 000 en ~ . --j E— 5 (-) 6 5 17 (:.. m - / in o I E?C LA .1. E-? --- SE-C 

F'r- c- s s a n y k e y t- o i - -- o n t j. rf 

—26— 
~ 

~ 

" 

°^ 

B. Screen DispIay of the DetaiIed CaIcuIations of 

OH RadicaI Addition tm the Aromat:ic Ring. 

OH Addition to Aromatic Rings 

de+ = Most negative va1ue of ep+ or em+ (-C=C 

Log Kar = -11.69 - 1.35 de+ cm3/molecule-sec 

Ring #1 Kar = 1.9187 E-12 cm3/molecule-sec 

TOTAL Kar = 1.9187 E-12 cm3/molecule-sec 

......................Assumed values designated by ** 

Press any key to continue 

-27- 
~ 

^ 

." 

Figure 6. Atmospheric Oxidation Program Data DispIay for the 

Compound m-MethyI Styrene (2~ I~l-Propene): 

Screen Display for OH Addition to the Arcmatic Ikiog 

and the ExperimentaI Data. 

OH Addition to Aromatic Rings 

_______________________________ 

de+ = Most negative value of ep+ or em+ (-C=C .020 

Log Kar = -11.69 - 1.35 de+ cm3/molecule-sec 

Ring #1 Kar = 1.9187 E-12 cm3/molecule-sec 

TOTAL Kar = 1.9187 E-12 cm3/molecule-sec 

......................Assumed values designated by ** 

ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

3 3 

3 Name: 2-Phenyl-1-propene (Wmethyl styrene) 3 

3 CAS Number: 00098-83-9 3 

3 Exper OH rate constant : 52.0 E-12 cm3/molecule-sec 3 

3 Exper Ozone rate constant : --- cm3/molecule-sec 3 

3 Exper NO3 rate constant : --- cm3/molecule-sec 3 

3 3 

3 3 

@DDDDDDDDDDDDDDDDDD4 Press any key to continue... CDDDDDDDDDDDDDDDDDDDYe 

-28- 
is reproduced with the original SMILES notation for a-methyl 

styrene. 

IV. Evaluation of the Atmospheric Oxidation Computer Program 

for Estimating kOH and the Experimentally Measured kOH 

Data Listed in the Program 

IV.A. Comments on the Group Rate Constants, Substituent Factors, 

and Other Parameters Used by the Atmospheric Oxidation 

Program 

The group rate constants, substituent factors, and other 

parameters are listed in Tables 1 through 9 for a large number of 

classes of compounds as obtained from Meylan (1990b). A few 

comments will be made in this section on the numerical values of 

these parameters listed in these tables. More details will be 

given in Sections IV.C. through IV.F. on specific classes of 

compounds and specific compounds in each of these classes. 

First, consider Table 1 which summarizes the group rate 

constants for hydrogen abstraction and radical reaction. The 

value of the group rate constant k(>C<) is listed as zero with 

one significant figure. However, this value is known much more 

accurately; conservatively, it is known to three significant 

figures. Therefore, it is recommended that AOP use k(>C<) _ 

0.000 which is consistent with the accuracy of the S/R 

relationships of Atkinson. 

Table 1 does not have an entry for H-atom abstraction from 

unsaturated carbon-carbon functional groups (i.e., =C-H). Even 

at temperatures up to 500 K, H-atom abstraction from these 

functional groups is zero [Atkinson (1987)]. Therefore, it is 

ic 

-29- 
~r 

> ~ 

Table 1. Group Rate Constants for Hydrogen Abstraction and 

Radical Reaction i 

GroupRate.Constant k X 10 12cm3 / molecule-sec 

k(-CH3) 0.144 

k(-CH2-) 0.838 

k(>CH-) 1.83 

k (>C<) 0 

k(-OH) 0.036' 

k(-NH2) 20 

k ( -NH- ) 60 

k(>N-) 60 

k ( -SH) 313 

k(-S-) 2.0 

k(-S-S-) 200 

k(>N-NO) 0 

k(>N-NO2) 0 

k[P(=0)] 0 

k[P(=S)] 55 

1Data from Table 1 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 

1.30, November 1990 [Meylan (1990b)]. 

ZThis group rate constant is only applicable to hydroxyl groups 

in alcohols and glycols. 

3Used only for aliphatic connections; connection to aromatics 

not included based upon experimental rate constant for 

thiophenol. 

-30- 
~ 

Table 2. Substituent F(X) Factors for Hydrogen Abstractioni 

(values marked with "**" are estimated/assumed values) 

ubstituent Factor 

1. -CH3 1.00 

2. -CH2- 1.29 

3. -CH2CL 0.57 

4. -CH2Br 0.57 

5. -CH2F 0.85 

6. -CH2C(=O)- 4.4 

7. -CH2ONO2 0.30 

8. -CH2CN 0.5 

9. -CH2I ** 0.57 

10. >CH- 1.29 

11. -CHCL2 0.57 

12. -CHF2 .0.10 

13. -CHBr2 ** 0.57 

14. -CHI2 ** 0.57 

15. >CHC ( -O ) - 4.4 

16. >CHONO2 0.30 

17. >C< 1.29 

18. -CCL3 0.09 

19. -CF3 0.075 

20. -CBr3 ** 0.09 

21. -CI3 ** 0.09 

22. >CC(-O)- 4.4 

23. >CONO2 0.30 

24. -CF2CL 0.025 

25. -F 0.099 

26. -CL 0.38 

27. -Br 0.30 

28. -I ** 0.30 

29. =O 8.8 

30. -Aromatic 1.0 

31. -OH 3.4 

32. -O- 6.1 

33. -ONO2 0.18 

34. -CN 0.14 

35. -OC(=O)R 1.5 

36. -C=(0)CL 0.5 

37. -C(=O)- 0.76 

38. -CHO 0.76 

39. -C(=O)OR 0.0 

40. >C=C< 1.0 

41. -C=C- 1.0 

42. -SH 9.0 

(given same value as -CH2Br) 

(given same value as -CHCL2) 

(given same value as -CHCL2) 

(given same values as -CCL3) 

(given same values as -CCL3) 

(given same value as -Br) 

-31- 
~ 

: -E 

Table 2. Continued 

ueQt Fact2r 

43. -S- 9.0 

44. -SS- 9.0 

45. -NH2 10 

46. -NH- 10 

47. -N< 10 

48. -NNO 10 

49. -NNO2 10 

50. -NO2 0.18 

51. -OP- 20 

52. -SP- 20 

53. -P- ** 1.0 

54. =P ** 1.0 

55. =N ** 1.0 

56. =S ** 9.0 

57. CH-Halogen ** 0.57 

58. S(+4)=O ** 99.0 

59. blank 1.0 

60. Missing 0.0 

61. -CH-2Halogens ** 0.57 

62. -C-3Halogens ** 0.09 

63. -CHF-Halogen ** 0.30 

64. -O-O- ** 50 

65. -O-N= ** 2.0 

66. >CNO2 ** 0.30 

67. >CHNO2 ** 0.30 

68. CH2-NO2 0.30 

69. CH2-0- 4.50 

70. 2nd -O- 1.00 

71. Sulfonic acid ** 0.20 

72. 2nd alkyl ketone 1.00 

73. -CH(Halogen)C=O ** 3.10 

74. -CH(NO2)C=O ** 1.3 

75. -CH(NO2)Halogen ** 0.21 

76. >C(NO2)C-0- ** 1.3 

77. >C(ONO2)C=0- ** 1.3 

78. -CH(ONO2)C-O ** 1.3 

79. >C-O- ** 4.5 

(new Atkinson value) 

(arbitrarily assigned a value of unity) 

(arbitrarily assigned a value of unity) 

(arbitrarily assigned a value of unity) 

(given same value as sulfur #s 42, 43, 44) 

(estimated by Asa Leifer) 

(based on dimethyl sulfoxide data) 

(given same value as -CHCL2) 

(given same value as -CCL3) 

(assigned a value between -CHF2 and 

-CHCL2) 

(based on experimental OH rate constants 

for methyl and t-butyl hydroperoxides) 

(arbitrarily assigned based on other 

values for oxygen and nitrogen 

connections) 

(given same value as 68) 

(given same value as 68) 

(new nitroalkane data) 

(new Atkinson value) 

(new Atkinson value) 

(arbitrary estimate) 

(data for cyclobutanone) 

(combination of previous) 

(combination of previous) 

(combination of previous) 

(combination of previous) 

(combination of previous) 

(combination of previous) 

(given same value as CH2-O-) 

~ Data from Table 6 in aroup Rate Constants and Substituent Values Used by the 

Atmospheric Oxidation Program, Version 1.30, November 1990 [Meylan (1990b)). 

-32- 
Y 

~ 

rTable 3. Factors Used for Aliphatic Ring Strain Effects' 

acto 

3-Membered Ring 0.017 

4-Membered Ring 0.22 

5-Membered Ring 0.80 

6-Membered Ring 1.00 

7 to 10-Membered Ring 1002 

' Data from Table 10 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan (1990b)]. 

2Note: aliphatic rings containing more than 10 members do not 

have any ring strain effect factor applied to them. 

-33- 
.F 

Table 4. Group Rate Constants for OH Radical Addition to 

Isolated Olefinic Units' 

Structure k X 10 12cm3 /molecule-sec 

CH2=CH- 26.3 

CH2=CH< 51.4 

-CH=CH- (cis-) 56.1 

-CH=CH- (trans-) 63.7 

-CH=C< 86.9 

>C=C< 110.0 

-CH=CH- (cyclic) 56.12 

' Data from Table 2 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 

1.30, November 1990 [Meylan (1990b)]. 

2 The group rate constant for cyclic alkenes such as cyclopentene 

and cyclohexene is assumed to be the same as the cis-iosmer 

value although the trans-isomer value yields slightly better 

estimates. 

-34- 
~ . 

W ~ 

Table 5. Group Rate Constants for OH Radical Addition to 

Conjuqated Olefinic Units i 

No. Alkyl Groups Structure k X 10 12cm3 /molecule-sec 

1 CH2=CH-CH=CH- 105 

1 CH2=CH-~=CH2 105 

2 

----------------------------------------------------------------- 

CH2=CH-CH=C< 135 

2 CH2=CH-~=CH- 135 

2 CH2=~-CH=CH- 135 

2 -CH=CH-CH=CH- 135 

2 CH2=?-~=CH2 135 

3 

----------------------------------------------------------------- 

CH2=CH-?=C< 180 

3 CH2=f-CH=C< 180 

3 -CH=CH-CH=C< 180 

3 CH2=?-?=CH- 180 

3 -CH=CH- ~=CH- 180 

-35- 
Table 5. Continued 

No. Alkyl Groups Structure k X 10 12cm3 /molecule-sec 

4 >C=CH-CH=C< 230 

4 -CH=C-CH=C< 

1 

230 

4 -CH=CH-C=C< 

1 

230 

4 CH2=C-C=C< 230 

4 -CH=C-C-CH- i I 

230 

5 

----------------------------------------------------------------- 

>C=C-C=CH1 1 285' 

5 >C=CH-C=C< 285' 

6 

----------------------------------------------------------------- 

>C=C-C=C< 3502 

~ Data from Table 5 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan (1990b)]. 

2 These values have been estimated .... estimates are based upon 

the increasing relationship for the 1 to 4 alkyl group 

structures. 

-36- 
Table 6. Group Rate Constants for OH Radical Addition to 

Alkyne Unitsi 

Structure k X 1012cm3 /molecule-sec 

CH$C- 6.4 

-CoC- 29.0 

~ Data from Table 3 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan (1990b)]. 

y ~ 

-37- 
Table 7. Group Rate Constants for OH Radical Addition to 

1,2-Dialkene (Allene) Units 1 

Structure k X 1012cm3 /molecule-sec 

CH2=C=CH- 31.0 

-CH=C=CH- 57.0 

CH2=C=C< 57.02 

-CH=C=C< 85.02 

>C=C=C< 110.02 

~ Data from Table 4 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan (1990b)]. 

2These values have been estimated .... the estimates are based 

upon analogy to the single unit olefin rate constants (see 

Table 2). 

-38- 
Table 8. Substituent Factors [C(X)] for OH Radical Addition to 

Olefins and Acetylenea l 

(values marked with "**" are estimated/assumed values) 

Substituent Factor 

1. -F 0.4 

2. -CL 0.20 

3. -Br 0.26 

4. -CH2CL 0.76 

5. -CN 0.15 

6. -CHO 0.26 

7. -C(-O)CH3 0.91 

8. -OCH3 1.3 

9. -0 1.0 

10. -I ** 0.26 (given same value as -Br) 

11. -CH2Br ** 0.76 (given same value as -CH2CL) 

12. -CH2F ** 0.76 (given same value as -CH2CL) 

13. -CH2I ** 0.76 (given same value as -CH2CL) 

14. -C-C ** 0.85 

15. not used 

16. -Phenyl ** 1.0 (Atkinson assumption, Int. J. Chem. Kinet. 

17. -C(-O)X ** 0.91 (given same value as -C(-O)CH3 

18. -OC ** 1.3 (given same value as -OCH3) 

19. -C . C** 1.10 (based on experimental rate constant for 

diacetylene) 

20. -S ** 1.0 ' (arbitrarily assigned a value of unity) 

21. -O ** 1.0 (arbitrarily assigned a value of unity) 

22. -P ** 1.0 (arbitrarily assigned a value of unity) 

23. -NO2 ** 0.5 (arbitrary estimate) 

24. -ONO2 ** 0.6 (arbitrary estimate) 

25. =S ** 1.0 (arbitrarily assigned a value of unity) 

26. -N ** 0.6 (arbitrary estimate) 

27. =P ** 1.0 (arbitrarily assigned a value of unity) 

28. =N ** 1.0 (arbitrarily assigned a value of unity) 

29. cyclic C-0 ** 0.20 (based on data for naphthaquinone) 

30. Missing 1.0 

31. R 1.00 (for an alkyl or a cycloalkyl group) 

19:822.) 

~ Data from Table 7 in Group Rate Constants and Substituent Values Used by the 

Atmospheric Oxidation Program, Version 1.30, November 1990 [Meylan (1990b)). 

-39- 
Table 9. Electrophilic Substituent Factors for OH Radical 

Addition to Aromatic Ringsi 

(values marked with "**" are estimated/assumed values) 

The q,+, and + values which are ti considered "assumed" values are taken 

directly from th~ 

n~ 

following reference: Brown, H.C. and Okamoto, Y(1958), 

"Electrophilic Substituent Constants", J. Am. Chem. Soc. 80: 4979-4987. 

Various "assumed" values are based on similar structures with known a + values. 

ga °p 

1. Amino (-NH2) -0.16 -1.3 

2. Dimethylamino (CH3-N-CH3) -0.16 ** -1.7 

3. Anilino (C6H5-NH-) -0.16 ** -1.4 

4. Acetylamino (CH3C(=O)-NH-) 0.21 ** -0.6 

S. Benzoylamino (C6H5-C(=O)-NH-) 0.21 ** -0.6 

6. Hydroxy (-OH) 0.121 ** -0.92 

7. Methoxy (-OCH3) 0.047 -0.778 

8. Phenoxy (C6H5-O-) 0.10 ** -0.50 

9. Methylthio (CH3-S-) 0.158 -0.604 

10. Methyl (CH3-) -0.066 -0.311 

11. Ethyl (CH3-CH2-) -0.064 -0.295 

12. Isopropyl (CH3-CH-CH3) -0.060 -0.280 

13. tert-Butyl (-C(CH3)(CH3)(CH3)) -0.059 -0.256 

14. Aromatic (phenyl) 0.109 -0.179 

15. Chloromethyl (-CH2-CL) 0.14 -0.01 

16. Fluoro (-F) 0.352 -0.073 

17. Bromo (-Br) 0.405 0.150 

18. Chloro (-CL) 0.399 0.114 

19. Iodo (-I) 0.359 0.135 

20. Trifluoro (-C-F3) 0.520 0.612 

21. Cyano (-C$N) 0.562 0.659 

22. Nitro (-NO2) 0.674 0.790 

23. Carboxy (-C(-O)-OH) 0.322 0.421 

24. Carbomethoxy (-C(-O)-O-CH3) 0.368 0.489 

25. Carboethoxy (-C(-O)-O-CH2-CH3) 0.366 0.482 

26. Carbethoxymethyl (-CH2-C(=O)-O-CH2-CH3) -0.01 -0.164 

27. Bromomethyl (-CH2-Br) 0.14 ** -0.01 ** 

28. Iodomethyl (-CH2-I) 0.14 ** -0.01 ** 

29. Nitrate (-ONO2) 0.674.** 0.790 ** 

30. Olefinic (-C=C) 0.02 ** 0.02 ** 

31. Acetylenic (-CsC) 0.21 ** 0.23 ** 

32. -O-R (assume methoxy) 0.047 ** -0.778 ** 

33. Phosporus (-P) 0.0 ** 0.0 ** 

34. Sulfur (-S) (assume methylthio) 0.158 ** -0.604 ** 

35. Carbonyl (-C-O) 0.10 ** 0.35 ** 

36. Aldehyde (-CHO) 0.36 ** 0.22 ** 

37. -C-CL3 0.55 ** 0.65 ** 

38. -C-Br3 0.55 ** 0.65 ** 

39. -C-I3 0.55 ** 0.65 ** 

40. -CH2-F 0.10 ** -0.05 ** 

41. -CH2- (assume ethyl) 0.06 ** -0.295 ** 

42. -CH- (assume isopropyl) 0.06 ** -0.280 ** 

43. -CH-Halogen (assume chloromethyl) 0.14 ** -0.01 ** 

44. >C< (assume t-butyl) -0.059 ** -0.256 ** 

-40- 
, 

<< 

Table 9. Continued 

~4n ap 

45. -NH- -0.16 ** -1.0 ** 

46. -N= -0.03 ** 0.15 ** 

47. -CH2-CN 0.17 ** 0.01 ** 

48. -N=N 0.30 ** 0.64 ** 

49. -O-C(=O)- 0.10 ** -0.10 ** 

50. Undefined 0.0 ** 0.0 ** 

51. -O-P 0.10 ** -0.20 ** 

52. -S-CN 0.30 ** 0.25 ** 

53. -S-CO 0.20 ** 0.15 ** 

54. -O-Halogen 0.15 ** -0.10 ** 

For the 55-59, the X refers primarily to halogens, but the program also 

considers nitro and cyano groups. The estimated values are taken from 

Atkinson publications pertaining to estimated rate constants for PCBs. 

55. -C6H4-X1 0.25 ** 0.02 ** 

56. -C6H3-X2 0.39 ** 0.22 ** 

57. -C6H2-X3 0.53 ** 0.42 ** 

58. -C6H1-X4 0.67 ** 0.62 ** 

59. -Phenyl-X5 0.81 ** 0.82 ** 

60. -S03 0.50 ** 0.50 ** 

61. -S-O -0.16 ** -1.30 ** 

1Data from Table 8 in Group Rate Constants and Substituent Values Used by the 

Atmospheric Oxidation Program, Version 1.30, November 1990 (Meylan (1990b)). 

-41- 
recommended that AOP adopt the group rate constant k(1, UNS CH) = 

0.000, list it in Table 1, and show it in all detailed 

calculations for H-atom abstraction from various unsaturated 

functional groups (=C-H). 

For the compound O,O-dimethyl chlorophosphorothioate, 

Atkinson et al. (1988) indicated that the group rate constant 

k(P-C1) = 0.00; and this should be added to Table 1 and to the 

computer program. Furthermore, the group rate constants k(>NNO), 

k(>N-NO2 ), and k[P(=0)] should be listed as 0.00. 

Inspection of the data in Table 1 indicates that k(-S-) = 

2.05 . This value is applicable to OH radical reaction in the 

presence of air at 1 atmosphere pressure and thus in the presence 

of oxygen. In the absence of oxygen, k(-S-) = 0.00 [Atkinson et 

al. (1988)]. These facts are pertinent since AOP incorrectly 

estimates k0H for acyclic and cyclic sulfides and compares the 

estimated values with the experimental values b . For example, for 

dimethyl sulfide, the recommended experimental value of kOHfrom 

Atkinson (1989) is 4.56, Table 24, which is valid in the absence 

of oxvqen. Therefore, in the data base for these compounds, the 

experimental value should be qualified to indicate that kOHwas 

It should be noted that for convenience, the factor 

10-12 cm3molecule- ls-1has been omitted. In all subsequent 

discussions on group rate constants, this factor will be 

omitted. In addition, in all subsequent discussions, all 

rate constants k(i) for all individual reaction pathways and 

kOgwill be written without the factor 10-12 cm3 molecule- is -1 . 

6 From Meylan (1990b), page 10, "Estimation Accuracy of AOP 

vs. PCFAP." 

_y 

-42- 
y : 

obtained from measurements in the absence of oxygen. If one 

wants to compare the estimated value with the experimental value, 

then kpH should be estimated under the boundary condition in the 

absence of oxygen and kOH = 2.59 [since k(-S-) = 0.00]. Thus, a 

footnote should be added to the numerical value of the group rate 

constant k(-S-) in Table 1[i.e., for k(-S-)]. The numerical 

value should be (2.0) 3and the footnote 3 at the bottom of this 

table should be --- 3Applicble at 298 K and a total pressure of 

1 atmosphere in air (and thus in the presence of oxygen). In the 

absence of air, and thus in the absence of oxygen, k(-S-) = 0.00. 

This is discussed in more detail in Section IV.E.i.b. 

From the experimental k OH data of diethylhydroxylamine, it 

was found that k(>NOH) = 0.00 [Leifer (1991a)] and this group 

rate constant should be entered into Table 1 and in the AOP 

Computer program. 

In Table 1, it is indicated that k(-SH) = 31 for RSH, where 

R is an alkyl group. This group rate constant is not valid when 

R is an aromatic group, based on the experimental rate constant 

for thiophenol [Meylan (1990b)]. For the present, this 

assignment can be tentatively used. However, the experimental 

kOH data from Barnes et al. (1986) may not be valid. Therefore, 

more experimental data is needed on thiophenol and other alkyl 

and aromatic thiols to confirm the assignment for k(-SH). 

In Table 1, the value of the group rate constant k(-OH) is 

only applicable to H-atom abstraction from the hydroxyl groups in 

alcohols and glycols and this fact must be noted in Table 1 for 

-43- 
> i 

i 

k(-OH) and in the computer program. This group rate constant is 

not applicable to H-atom abstraction from the hydroxyl groups in 

carboxylic acids and alkyl peroxides. See Section IV.C.3.b. for 

the discussion of the estimation of k OH for carboxylic acids and 

Section IV.C.4.b. for the discussion of the estimation of k OHfor 

alkyl peroxides. 

In Table 2, item, No. 57, should be changed to F(R 2 CHC1) _ 

0.57 [estimated by Leifer from the experimental data of 2,3- 

dichlorobutane from Mill et al. (1982); and an additional item 

F(R2CH- 1 Halogen **) = 0.57 (based on the assignment in No. 57) 

should be added before item 60. 

The substituent factor F(-0-0 **) = 50 should be deleted 

from Table 2 because of the erroneous assumption that k(-OH) _ 

0.036 for methyl and t-butyl hydroperoxide. For the details, see 

Section IV.C.4.b. Similarly, the substituent factor dimethyl 

sulfoxide, No. 58, Table 2, should be deleted since it is 

expected that the sulfoxide would be readily oxidized to the 

sulfone. For the details, see Section IV.E.2.b. 

Table 4 lists the group rate constant for the functional 

group >C=C< as 110.0; it should be 110 based on the experimental 

kOHdata for 2,3-dimethyl-2-butene and the recommended value by 

Atkinson (1986,1989). Therefore, the last significant figure 

should be deleted. Similarly, the group rate constant for -C=Cin Table 6 should be 29 and not 29.0 based on the recommendation 

of Atkinson (1987, page 814). 

-44- 
In Table 8, some of the substituent factors C(X) are marked 

with the symbol ** to indicate that they are based on estimated/ 

assumed values. However, if a substituent factor is based on 

experimental kOg data, then the symbol ** should be omitted. For 

example, consider diacetylene, in Table 8, No. 19; this 

substituent factor is listed as {C[-COC-**]} = 1.10 (based on the 

experimental data for diacetylene). The entry in this table 

should be No. 19 C[-C=C-] = 1.10 (based on the experimental data 

of diacetylene). Similar comments are applicable to the 

substituent factors C(X) for numbers 29 and 16, Table 8. 

Therefore, for the substituent factor C[Cyclic C=0 **] (No. 29), 

the double asterisks should be removed since the value is based 

on the experimental kOH data of 1,4-naphthoquinone; similarly, 

for No. 16, C(phenyl **) = 1.0 should be C(phenyl) = 1.00, based 

on the experimental kCH data of styrene, c- and Q-methyl styrene, 

and fl-dimethyl styrene [Atkinson (1987, page 828)]. These 

comments also apply to the substituent factors F(X) marked with 

** in Table 2. 

In Table 8, No. 14 is listed as C(CmC- **) = 0.85 without 

any notation as to how this value was derived. Since this 

represents an estimated/assumed value, a qualifying statement 

should be added to designate how this assignment was made. 

Finally, in Table 9, the vm value for substituent -CH 2 - (No. 

41) is listed as 0.06 ** by analogy with the ethyl group. 

However, Qm for the ethyl group is -0.064 and this value should 

be listed in No. 4, Table 9. 

., 

-45- 
IV.B. Some Comments on Hydroxyl Radical Addition to 

Heteroaromatic and Fused Polyaromatic Ring Systems 

Meylan (1990b) developed elegant S/R relationships for 

estimating the second-order rate constant for OH radical addition 

to heteroaromatic (mono and fused polycyclic) rings and to fused 

polynuclear aromatic hydrocarbon (PAH) rings. For monocyclic 

heteroaromatic compounds (ar l ), AOP uses equation 24; for fused 

ring polynuclear aromatic hydrocarbon compounds (PAH), AOP uses 

equation 29; and for fused ring polynuclear heterocyclic 

compounds (PAH'), AOP uses equation 30. The first term in each 

of these equations [i.e., Ai, Bi, and Bi, respectively) was 

derived by Meylan from: (1) the experimental values of k OHfor 

the basic, or parent, heterocyclic ring or the fused polynuclear 

aromatic hydrocarbon ring structure; or from (2) the experimental 

ionization potentials for the parent fused ring polynuclear 

aromatic hydrocarbons and fused ring polynuclear heteroaromatic 

compounds. Tables 10 and il list the values of Ai and Bi, 

respectively, for various heteroaromatic ring structures and 

polyaromatic hydrocarbons derived from the experimental k OHdata 

for the parent aromatic compounds. Tables 12 and 13 list the 

values of Bi and Bi , respectively, derived from the experimental 

ionization potentials of the parent ring compounds. 

AOP has a SMILES interpreter which allows it to identify the 

parent aromatic ring structure and assign it the appropriate 

value of Ai, Bi, or Bi . AOP then adjusts this value for any 

substituent on the ring by utilizing the appropriate substituent 

-46- 
., 

., 

Table 10. Experimental Values of Ai for Some Monocyclic 

Heteroaromatic Compounds* 

Heterocyclic Aromatic Ring Structure 

Pyrrole 

Furan 

Thiofuran 

Imidazole 

Oxazole 

Thiazole 

Pyridine 

1,3,5-Triazine 

Experimental Value of Ai 

(10-12 cm3 molecule- ls-1 ) 

110.0 

40.5 

9.53 

36.0 

9.1 

1.4 

0.37 

0.15 

* Data from page 7 of the User's Guide for the Atmospheric 

Oxidation Program, Version 1.10, November 1, 1990 [Meylan 

(1990b)]. 

-47- 
R: 

t 

i r 

Table 11. Experimental Values of Bi for Some Polynuclear 

Aromatic Compounds* 

Experimental Value of Bi 

Polynuclear Aromatic Ring Structure (10-12 cm3 molecule- ls -1 ) 

Naphthalene 21.6 

Anthracene 110.0 

Phenanthrene 31.0 

* Data from page 7 of the User's Guide for the Atmospheric 

Oxidation Program,*Version 1.10, November 1, 1990 [Meylan 

(1990b)]. 

-48- 
~ . 

~ . 

Table 12. Values of Bi for Polynuclear Aromatic Hydrocarbon 

Structures Derived from Experimentally Measured 

Ionization Potentials* 

Polynuclear Aromatic Ring Structure 

4 Fused Benzene Rings 

5 Fused Benzene Rings 

6 Fused Benzene Rings 

Assigned Value of 

Bi Based on the 

Experimentally Measured 

Ionization Potential 

(10 -12 cm3 molecule-ls -1 ) 

80.0 

150.0 

200.0 

* Data from page 7 of the User's Guide for the Atmospheric 

Oxidation Program, Version 1.10, November 1, 1990 [Meylan 

(1990b)]. 

-49- 
Y 

f '(~ 

Table 13. Values of Bi for Polynuclear Heteroaromatic 

Structures Derived from Experimentally Measured 

Ionization Potentials* 

Assigned Value of Bi 

Based on the Experimentally Measured 

Ionization Potential 

Polynuclear Heteroaromatic Structure (10 -12 cm3 molecule- ls-1 ) 

Quinoline 6.5 

Isoquinoline 6.5 

Quinoxaline 2.0 

Quinazoline 2.0 

Acridine 27.5 

* Data from page 7 of the User's Guide for the Atmospheric 

Oxidation Program, Version 1.10, November 1, 1990 [Meylan 

(1990b)]. 

 ~ 

-50- 
~ - 

factors vm and vP for the substituents on the ring. For 

example, for 1-chloronaphthalene, the•SMILES interpreter in AOP 

identifies the parent naphthalene ring and selects the value of 

Ai for this ring. AOP then adjusts this.value by considering 

the effect of the chlorine substituent on the reactivity of the 

ring. 

It should be noted that Meylan did not develop S/R 

relationships for fused ring aromatic compounds containing five 

membered heterocyclic rings. For example, AOP cannot estimate 

kpg for benzothiazole. In principle, however, the basic 

concepts of Meylan can be used. For example, if k OH is 

measured for benzothiazole, then Bi from equation 30 can be 

determined. Therefore, with this value of Bi, kOHcan be 

estimated for substituted benzothiazoles utilizing the 

appropriate substituent factors v ~ and vP for the substituents 

on the ring. 

More experimental kOg data is needed on a number of 

additional derivatives of these heteroaromatic (ar'), polynuclear 

aromatic hydrocarbons (PAH), and polynuclear heteroaromatic ring 

(PAH') structures to confirm the S/R relationships of Meylan 

(1990b) [i.e., confirm the validity of equations 24, 29, and 30]. 

It should be noted that in Tables 10, il, and 12, AOP lists 

a few of the values of Ai and Bi to four significant figures. At 

best, the experimental data used to derive these constants are 

only valid to three significant figures. Therefore, it is 

-51- 
recommended that the values of Ai and Bi for pyrrole, anthracene, 

and for 4, 5, and 6 fused benzene rings should be listed to three 

significant figures. 

IV.C. H-Atom Abstraction from C-H and -OH Groups by Hydroxyl 

Radicals 

IV.C.1. Saturated Alkanes 

IV.C.i.a. Evaluation of the Experimental kOg Data 

Tables 14.A. and 14.B. summarize the pertinent experimental 

kOg data at 298 K for the reaction of OH radicals with acyclic 

and cyclic alkanes, respectively, as obtained from AOP and the 

literature. For this class of compounds, hydroxyl radical 

reaction only involves the abstraction of H-atoms from the 

various primary, secondary, or tertiary C-H groups. The first 

column in these two tables lists the name of each alkane; the 

second column lists the experimental value of kOHat 298 K in AOP 

[Meylan (1990b)] and is labeled Experimental/AOP; the third 

column lists kOH at 298 K as obtained by Leifer from Atkinson 

(1989) and/or from the literature and is labeled 

Experimental/(a); the fourth column lists the.estimated value of 

kOH at 298 K as obtained from AOP and is labeled Estimated/AOP; 

and finally the fifth column lists the estimated, hand calculated 

(HC), value of kOH at 298 K as obtained by Leifer using the S/R 

relationships of Atkinson and is labeled Estimated/HC. 

Atkinson (1989) critically analyzed the available 

experimental kOH data and recommended the best values along with 

the rationale behind each recommendation and the uncertainty for 

a 

-52- 
Table 14.A. Comparison of the Estimated Values of kOH at 298 K for 

Saturated Acyclic Alkanes from the Atmospheric Oxidation 

Computer Program (AOP) and from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the Literature Versus the 

Experimental kOH Data Reported in AOP 

10 12k (cm3molecule- ls -1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Methane -44-$a -k 0.00841 0.00836* 0.00841b (c) 

Ethane ?q-g4k°o 0.268 0.268* 0.288 0.288 

Propane 74.,q T-to 1.15 1.15 * 1.21 1.21 

H-Butane 2.54 2. 54* 2.53 2.53 

2-Methylpropane ~S a g"~ 2.34 2.34* 2.39 2.39 

n-Pentane lb9-& 6- 3.94 3.94* 3.93 3.93 

2-Methylbutane 3.90 3.9* 4.00 4.00 

2, 2 -D imethy 1propane 0.849 0.849* 0.743 0.743 

n-Hexane 3 5.61 5. 61* 5.32 5.32 

2-Methylpentane 107 - 8 3- S 5.60 5.6* 5.39 5.39 

3-Methylpentane v 5.70 5.7* 5.77 5.77 

2,2 -Dimethylbutane 75- 83 - 2 2.32 2.32* 1.82 1.83 

2, 3 -Dimethy lbutane 7y-a C)- F 6.20 6.2* 5.46 5.46 

n-Heptane IyV -8a -s' 7.15 7.15* 6.72 6.71 

2,2-Dimethylpentane ~'JO' 3S"a 3.37 3.37d 3.22 3.22 

2,4-Dimethylpentane 5.16 5.16d' 6.86 6.85 

2, 2, 3-Trimethylbutane ,V6zf- 0 ~O-2. 4.23 4. 23* 3.29 3.30 

n-Octane ///-- 10.5 - ~ 8.68 8. 68* 8.11 8.11 

2,2-Dimethylhexane 5gO- -:T3-S' 4.83 4.83d 4.61 4.61 

2, 2, 4-Tr imethy 1pentane 54/0 -Ey-/ 3j 3.68* 4.68 4.68 

2,3,4-Trimethylpentane ~ 6.97e 8.70 8.70 

SGS- ~5--3 

M*C 
Table 14.A. Continued 

10 12k (cm3 molecule- ls -1 ) 

Chemical Experimental Estimated 

AOP ( a) AOP HC 

2,2,3,3-Tetramethylbutane 1.08 1.08* 1.11 1.11 

g-Nonane 10.20 10.2* 9.51 9.50 

2-Methyloctane 10.1 10.1d 9.58 9.58 

4-Methyloctane 9.72 9.72d 9.95 9.95 

2,3,5-Trimethylhexane/u&) -s3-0 7.88 7.88d 10.1 10.1 

n-Decane la q- /fS= ,S 11.6 11.6* 10.9 10.9 

D-Undecane //a a -o2/ -~ C' I H.) y 13.2 13 . 2* 12.3 12.3 

n-Dodecane l l a -- ya -3 14.2 14 . 2* 13.7 13.7 

n-Tridecane 6,9 y-SO -' 16.0 16* 15.1 15.0 

n-Tetradecane &aq- ,;9 - `f 19.2 19.2* 16.5 16.5 

n-Pentadecane 6 aq -- Co a 22.2 22.2f 17.9 17.9 

n-Hexadecane 24.9 24.9f 19.3 19.3 

aExperimental values from Atkinson (1989) and the literature. 

b Estimated value is based on the measured value. 

c Cannot be estimated by the S/R methods of Atkinson. 

d a Experimental value from Behnke et al. (1988). 

Experimental value from Atkinson et al. (1984). 

e Experimental value from Harris and Kerr (1988). 

f Experimental value from Noltinq et al. (1988). 

-54- 
5 

.~ 

~ 

~ 

~ 

a a 

• Table 14.B. Comparison of the Estimated Values of kOH at 298 K for 

'= Saturated Cyclic Alkanes from the Atmospheric Oxidation 

Computer Program (AOP) and from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the Literature Versus the 

Experimental kOH Data Reported in AOP 

10 12 k (cm3 molecule- ls -1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Cyclopropane 0.07 0.071b 0.0711 0.0711 

.1-Propylcyclopropane &96- 2.84 2. 84c 2.85 2.85 

Cyclobutane 1.20 1.2d 1.23 1.23 

Cyclopentane 5.16 5.16* 5.58 5.58 

Cyclohexane //c)- 8a-° 7.49 7.49* 8.37 8.37 

Methy lcyc lohexane / o$'- a 10.4 10.4e 10.2 10.2 

1,1,3-Trimethylcyclohexane 8.73 8.73f 9.18 9.18 

307- 3-&(."3 

Cycloheptane 12.5 12.59 9.76 9.77 

Cyclooctane 99a-& 4-*r 13.7 13.7h 11.2 11.2 

Bicyclo [2.2.1] heptaneM-23-2 5.49 5.49 1 9.49 9.49 

Bicyclo [ 2. 2. 2] octane 2f ~o- 33-I 14.7 14.7i 16.2 16.2 

Bicyclo [3.3.0] octane69yg~~y 11.0 11.0 1 10.4 10.4 

cis-Bicyclo [4.3.0] nonane 17.2 17.2 1 14.1 14.1 

trans-Bicyclo [4.3.0] nonane 17.6 17.6 1 14.1 14.1 

cis-Bicyclo [4.4.0] decane 19.9 19.9 1 19.0 19.0 

/930/_ - 

c ~oN ~ e 

trans-Bicyclot4.4.0]deoane 20.4 20.4 1 19.0 19.0 

/F~7:3- c~ -'~ C 

Tricyclo [5.2.1.0 2,6 ] decane 11.3 11.3 1 12.3 12.3 

Tricyclo [3.3.1.1 3,7 ] decane 22.6 22.67 24.1 24.1 

a Experimental values from Atkinson (1989) and the literature. 

b Average value from the experimental data of Zetzsch (1980) and Jolly et al. 

(1983). 

c Experimental value from Atkinson and Aschmann (1988). 

d Experimental value from Gorse and Volman (1974). 

e Experimental value from Atkinson et al. (1984). 

f Experimental value from Behnke et al. (1988) as reported in Atkinson (1989). 

g Average value of the experimental data of Zetzsch (1980) and Jolly et al. 

(1985). 

h Experimental value from Behnke et al. (1988) as reported in Atkinson 

, (1989). 

1 Experimental value from Atkinson, Aschmann, Carter (1983a). 

7 Average value from the experimental data of Atkinson, Aschmann, and Carter 

(1983a) and Behnke et al. (1988). 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

M&C 
each recommendation. These recommended values have an asterisk 

after each value. 

In general, the experimental values of k OH listed in AOP are 

the same as those obtained by Leifer; there are, however, a few 

differences. For methane, the recommended Atkinson value is 

0.00836* while AOP lists 0.00841. For 2,3,4-trimethylpentane, 

the kOH value of 6.97 was obtained by extrapolation of the data 

and Kerr (1988) and appears to be the best value. The best value 

of kOH for cyclopropane should be 0.071 as obtained by averaging 

the data of Zetzsch (1980) and Jolly et al. (1985) rather than 

the value of 0.07 listed in AOP. For a few compounds, the 

incorrect number of significant figures was cited by AOP; the 

recommended values list two significant figures whereas AOP lists 

three significant figures. For example, for 2-methylbutane, the 

Atkinson recommended value is 3.9* while AOP lists 3.90. For 

cyclobutane, the value of kOH reported by Gorse and Volman (1974) 

and Atkinson (1989) is 1.2 and not 1.20 as listed in AOP. The 

experimental kOH data of Gorse and Volman is only good to two 

signif icant f igures . 

It should be noted that the names of two tricyclic decanes 

{tricyclo [5.2.1.0] decane and tricyclo [3.3.1.1] decane} entered 

in AOP are incorrect. The correct names should be tricyclo 

[5.2.1.0 2

. 6 ] and tricyclo [3.3.1.1 3 j] decane since the 

superscript numbers on the last digit must be specified to 

identify the bridgehead carbons on the last ring. Finally, the 

a~ 

-56- 
name of inethylcyclohexane is the correct name and not 

1-methylcyclohexane as listed in AOP. 

IV.C.l.b. Evaluation of the Estimated kOH Data 

A preliminary evaluation of the AOP computer program [Meylan 

(1990a)] in July 1990 indicated that for some bicyclic and 

tricyclic alkanes, the method of estimating kOH in AOP was 

incorrect. The AOP computer program did not use the ring strain 

factors [F(3), F(4), F(5), or in Meylan's notation RS3, RS4, RS5] 

correctly in the calculations. The discrepancies were discussed 

with Meylan by phone and a set of the calculations were sent to 

him for evaluation. As a result, Meylan (1990b) revised the AOP 

computer program for these types of compounds to accurately 

reflect the Atkinson S/R relationships for strained ring 

compounds [Version 1.30, November 1, 1990]. 

In evaluating the estimated values of k OHby AOP and HC, a 

few comments can be made about the number of significant figures 

used. In general, the summary table in AOP lists the estimated 

kOH with a maximum of six significant figures and the detailed 

calculations list k(la) or k(ic) with a maximum of five 

significant figures. However, the group rate constants kp, k s , 

and ke , [or kprim• ksec• and ktert in Meylan's notation] and the 

substituent factors F(CH3-), F(-CH2-), and F(>C<) are, at best, 

known to three significant figures. Therefore, it is recommended 

that AOP show the detailed calculations with four significant 

figures and list k(la) or k(ic), or k(la) + k(lc), and kOH in the 

, 

-57- 
summary table rounded off to 3 significant figures. These 

comments on the use of an excessive number of significant figures 

apply to all classes of chemicals and specific chemicals. 

Comparison of the estimated values of k OH from AOP with 

those from HC (after rounding off all estimated values to three 

significant figures) in the last two columns in Tables 14.A. and 

14.B. indicates that, except for methane, the values are 

essentially the same. The trivial differences in the last digit 

are due to the method of rounding off the last digit in HC. For 

methane, AOP lists a value of 0.00841 which is the experimental 

value [which really should be 0.00836* as recommended by 

Atkinson] whereas HC does not list a value; kOH cannot be 

estimated by the S/R relationships of Atkinson for this compound. 

The number of significant figures for RS3, RS4, and RS5 for 

strained rings is incorrect. For example, for cyclobutane, RS4 = 

0.22000 is used in the detailed calculation section. However, 

for RS4, Atkinson listed it as 0.22. 

The detailed calculations for H-atom abstraction are 

somewhat confusing when the ring strain factor is used. For 

example, for bicyclo [2.2.1] heptane, AOP gives 

ksec = 0.838 F(-CH2-)F(>CH-)(RS5)(RS5) 

= 0.838(1.29)(1.29)(0.64) 

= 0.892 

It seems to me that a more consistent notation for RS5 would be 

(RS5) 2=(0.80) 2 rather than (RS5)(RS5) = 0.64. Therefore, ksec 

-58- 
should read 

ksec.= 0•838 F(-CH2-)F(>CH-)(RS5) 2 

= 0.838 (1.29)(1.29)(0.80) 2 

= 0.892 

or 

ksec a 0.838 F(-CH2-)F(>CH-)(RS5)(RS5) 

= 0.838(1.29)(1.29)(0.80)(0.80) 

= 0.892 

IV.C.2. Haloalkanes 

IV.C.2.a. Evaluation of the Experimental kOH Data 

Table 15 summarizes the pertinent experimental kpg data at 

298 K for the reaction of OH radicals with haloalkanes as 

reported in AOP, in Atkinson (1989), and in the literature. In 

general, the literature values listed in the column 

Experimental/(a) are the same as those in the column 

Experimental/AOP; there are, however, some differences. For 

1,1,1-trifluoroethane, AOP lists a value of 0.017, a ten-fold 

higher value than the correct value of 0.00171 from Martin and 

Paraskevopoulos (1983) and Atkinson (1989). [Please note that 

these values are listed in the units 10 -12 cm3 molecule - is-1 rather 

than 10 -14cm3molecule- ls-1 as listed in Table 15; see footnote 5, 

page 42.] For 1,1,2-trichloroethane, the extrapolated value from 

the data of Jeong and Kaufmann (1979) and Jeong et al. (1984) 

obtained by Leifer is 0.324 while AOP lists a value of 0.328. 

For three haloalkanes, AOP does not list an experimental value 

-59- 

x . 

k. ;: 
Table 15. Comparison of the Estimated Values of kOH at 298 K for Haloalkanes , 

from the Atmospheric Oxidaticn Computer Program (AOP) and from a 

Hand Calculation (HC) and the Experimental kQH Data Reported in the 

Literature Versus the Experimental kOH Data in AOP 

10 14k (cm3 molecule - ls-1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Fluoromethane ,593 - s3" =) 1.68 1. 68 * 1.43 1.43 

Chloromethane 7.41 °8'.7-3 4.36 4. 36* 5.47 5.47 

Bromomethane,7y-g3-y 4.02 4.02* 4.32 4.32 

Difluoromethane 7,1 -/0-6- 1.09 1. 09* 0.82 0.821 

Fluorochloromethane 30-4 4.41 4.41* 3.15 3.15 

Dichloromethane 14.2 14.2* 12.1 12.1 

Tr i f luoromethane 1,~ -y& 0.024 0. 024b 0.18 0.178 

Difluorochloromethane 75'-N5 - w 0.468 0.468* 0.682 0.682 

Fluorodichloromethane 75-Y3-4/ 3.03 3.03* 2.62 2.62 

Trichloromethane 67 - "-3 10.3 10.3* 10.0 10.0 

Fluoroethane 35.3 - .3G- 23.2 23.2c 20.5 20.5 

Chloroethane -7,5=o0- 3 39 39* 40.1 40.0 

1,1-D i f luoroethane 3.4 3. 4* 3.23 3.23 

1,2-Difluoroethane 70--(a 11.2 11.2d 14.1 14.1 

1,1-Dichloroethane-7s -3y-3 26 26. Oe 34.6 34.6 

1,2-Dichloroethane /0 7-U0 a 22 22.0e 36.3 36.3 

1, 2-Dibromoethane /06 _ 93- 4l 25 25. Oe 28.7 28.7 

1,1,1-Trifluoroethane4/ao- 416-,~ 1.7 0.171d 1.08 1.08 

1, 1, 1-Trichloroethane 3/-SS=Ca 1.19 1.19* 1.30 1.30 

1,1-Difluoro-l-chloroethane 0.358 0.358* 0.36 0.360 

€~ 1,1,2-Trifluoroe ~s-~ h.ane o'06'V 1.8 1.83 d 2.35 2.35 

1, 1, 2 -Tr ichloroethane q- oO -SS 32.8 32.4f 33.2 33.3 

1,1,1,2-Tetrafluoroe 6

thane_a 0.854 0.854* 0.62 0.622 

1-Chloro-2,2,2-Trifluoro ~ 1.62 1.62* 2.39 2.39 

ethane 

1,1,2,2-Tetrafluoroethane (j) 0.679 0.36 0.359 

3s1-35 3 

-60- 
D ♦ 

- Table 15. Continued 

10 14 k (cm3 molecule- ls-1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Pentafluoroethane-35-y--'''-( ~' ~~

NFS 0.25 0.249d 0.13 0.135 

1-Chloro-1,2,2,2-Tetrafluoroethane 1.02 1.02* 0.52 0.516 

~ 6.3' ~~7- e~ c~i-~ c~ F 

1,1-Dichloro- ~,2,2-Trifluoroethan e 3.35 3.35* 1.98 1.98 

30(o- 83"s;t Cc26fCQsF3 

1,2-Dibromo-3-chloropropane ~-/a-~ 44 43.5k 50.3 50.3 

2-Chlorobutane qg-86--y (j) 

230 1 164 164 

2, 3-Dichlorobutane ?.Sg) - (j ) 96 1 95.7 95.7 

a Experimental values from Atkinson (1989) and the literature. 

b since the experimental data was obtained at temperatures > 387 K, the value 

at 298 K should be used with caution [Atkinson (1989)]. 

c Experimental value from Nip et al. (1979). 

d Experimental value from Martin and Paraskevapoulos (1983). 

e Experimental value from Howard and Evenson (1976). 

f Extrapolated from the experimental data of Jeong and Karfmann (1979) and 

Jeong et al. (1984). 

g Extrapolated from the experimental data of Clyne and Holt (1979). 

h Experimental value from Tuazon et al. (1986). 

1Experimental value from Mill et al. (1982). 

j No experimental value given in the AOP data base. 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-61- 
(i.e., for 1,1,2,2- tetrafluoroethane, 2-chlorobutane, and 2,3- 

dichlorobutane). For six compounds, the literature values have 

three significant figures while AOP lists two significant figures 

[e.g., for 1 1 1-dichloroethane, the literature value of Howard and 

Evenson (1976) is 0.260 while AOP lists 0.26]. 

IV.C.2.b. Evaluation of the Estimated kOHData 

A comparison of the estimated values of kOH by AoP with HC 

in Table 15 indicates that they are essentially the same. The 

only differences being that in a few cases, AOP rounds off the 

estimated values to two significant figures. The estimated 

values of kOH are good to three significant figures. For 

example, for trifluoromethane, the estimated value of kOHby HC 

is 0.178, while AOP rounds it off to 0.18. 

IV.C.3. Carbonyl Compounds 

IV.C.3.a. Evaluation of the Experimental kOH Data 

Table 16 summarizes the pertinent experimental kOHdata at 

298 K for the reaction of OH radicals with 57 carbonyl compounds 

as reported in AOP, in Atkinson (1989), and in the literature. 

These carbonyl compounds can be divided into several classes of 

compounds: il aldehydes, 19 ketones, 3 c-dicarbonyls, 1 acyl 

halide, 18 esters, and 5 carboxylic acids. First, consider all 

the compounds except the carboxylic acids. In these classes of 

compounds, 12 of them listed by AOP had experimental kOgdata 

with two significant figures. If the original literature sources 

and Atkinson (1989) are checked, a11 the kOHdata are listed with 

three significant figures (e.g., formal, 3-hexanone, n-butyl 

r = 

s 

-62- 
, 

s ~ 

Table 16. Comparison of the Estimated Values of k OHat 298 K for Carbonyl 

Compounds from the Atmospheric Oxidation Computer Program (AOP) and 

from a Hand Calculation (HC) and the Experimental kQH Data Reported 

in the Literature Versus the Experimental k OHData in AOP 

10 12k (cm3 molecule- ls-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP($Error)o HC 

A. ALDEHYDES 

Formal 5-0-00 - O 9.7 9.77* 7.37 7.37 

Ethana 1'7S-C~ ~ - u' 15.8 15 . 8* 16.2 16.2 

Propanal 1,23° 3 9 "& 19.6 19. 6* 22.0 22.0 

Butanal /,)3- ;4z-_.? 23.5 23.5* 25.5 25.5 

2-Methyl Propanal 75 26.3 26.3* 23.4 23.4 

Pentanal 110 -.3 28.5 28 . 5* 27.6 27.6 

3-Methylbutanal Sqp - 6(0- 3 27.4 27.4* 30.0 30.0 

2, 2-Dimethylpropanal 6-1)- a'9 J,3 26.5 26. 5* 22.7 22.7 

Trichloroacetaldehyde 15-- 8-7-!0 1.73 1.73a' 1.45 1.45 

Hydroxyethanal / ~~- ~~,-~ 9.9 9.9b 23.0 23.0 

(Glycolaldehyde) 

Pentane-1,5-Dial 111-3o-g 23.8 23.8c 46.9 46.9 

B. ACYCLIC KETONES 

Propanone &7 - 6 41-1 0.226 0.226* 0.219 0.219 

2-Butanone 1.15 1. 15* 1.38 1.38 

2-Pentanone 4.9 4.9* 4.80 4.81 

3-Pentanone 2.0 2.0* 2.54 2.55 

2-Hexanone 9.1 9.1* 6.95 6.96 

3-Hexanone 5gg- -;Jg-v 6.9 6.90d 5.97 5.97 

4-Methy1-2-pentanone 14.1 14.1* 9.35 9.35 

3, 3-Dimethyl-2-butanone ~s c~~ __ ~, 1.21 1. 21e 2.01 2.01 

2-Heptanone 110-43-0 8.67 8.67e 8.35 8.35 

-63- 
Table 16. Continued 

10 12 k (cm 3 molecule - ls-1 ) 

Chemical Class/C mical Experimental Estimated 

AOP (a) AOP($Error)o HC 

2,4-Dimethyl-3-pentanone 5.38 5.38d 5.32 5.31 

2-Octanone 3 - /~, 10.0 11.0e 9.74 9.74 

2-Nonanone 12.2 12.2e il. i 11.1 

2,6-Dimethyl-4-heptanone` 27.5 27.5* 18.5 18.5 

2-Decanone ~~j_3 -- .S~ ~~ 13 . 2 13 . 2 e 12.5 12.5 

2,4-Pentanedione 1.15 1.15f 0.703 0.703 

2,5-Hexanedione //D -/,3- 4/ 7.13 7.13f 5.82 5.82 

C. CYCLIC KETONES 

Cyclobutanone /1 q1 -9S' 0.87 0.87f 1.17 1.17 

Cyclopentanone/ 9U- c?a - 3 2.94 2.94f 8.92 8.92 

Cyclohexanone /og_ 9~(- / 6.39 6.39f 12.6 12.6 

D. ac-DICARBONYLS 

Glyoxal 11.4 11.4* 24.5 24.5 

Methylglyoxal 17.2 17.2* 12.3 12.3 

Biacetyl q31- 0.3-$ 0.238 0.238* 0.219 0.219 

E. ACYL CHLORIDES 

Acetyl chloride -7.S- 3(o-S 0.068 0.0689 0.0720 0.0720 

F. ESTERS 

Methyl formate /O:T-,3/-3 0.23 0.227h 0.216 0.216 

r ; 

-64- 
Table 16. Continued 

10 12k (cm3molecule- ls-1 ) 

Chemical C las /Chemical Experimental Estimated 

'~ AOP (a) AOP(%Error)o HC 

Ethyl formate 109-9L~-41 1.0 1.02h 1.44 1.44 

n-Propyl formate //0- L/-7~ 2.4 2.38h 2.89 2.89 

n-Butyl formate JL 3.1 3. 12h 4.28 4.28 

Methyl acetate 0.34 0.3411 0.216 0.216 

Ethyl acetate /q/- 7$ -(0 1.6 1.6* 1.44 1.44 

n-Propyl acetate /09-0 0-44 3.4 3.4* 2.89 2.89 

i-Propyl acetate 3.4 3.4* 3.12 3.12 

}1-Butyl acetate 4.2 4. 2* 4.28 4.28 

$-Butyl acetate /o,5--440-4i (n) 5.5* 4.99 4.99 

Ethyl propionate 2.1 2.14 1 1.63 1.63 

}1-Propyl propionate /U& - 34~1 S 4.0 4.02h 3.08 3.07 

Methyl butyrate (p03' ~O -7- 3.0 3. 04h 1.48 1.48 

Ethyl butyy(rate 105 -S`f' `1 4.9 4. 94h 2.71 2.71 

n-Propy 1 butyrate /ciS 'Ga 4-&' 7.4 7. 41h 4.16 4.16 

n-Butyl butyrate ln2- a) --~- 10.6 10.6h 5.55 5.55 

Ethoxyethyl acetate///-/S- g 13.0 13h

1 

14.0 14.0 

Methyl trifluoroacetate 

4131 --~~ - v 

0.05 0.052h 0.216 0.0518 

G. CARBOXYLIC ACIDS 

Formic acid 1 $ -4, 0.45 0.45* 0.4367 (-3) (k) 

Acetic acid (o 41- /y - 3'" 0.74 0.74 1 0.145 (-80) (k) 

Propionic acid :79-pg-1 1.22 1.22 1 0. 859 (-30) (k) 

L-Butyric acid 9Z- 2.4 2.4m 2.12(-12) (k) 

.i-Butyric acid 2 2.00 2.00 1 1.80 (-10) (k) 

a Experimental values from Atkinson (1989) and the literature. 

a ~ Experimental value from Nelson et al. (1984) as reported by Atkinson 

(1989). 

-65- 
Table 16. continued 

bExperimental value from Niki et al. (1987) 

cExperimental data from Rogers (19891. This value of kOH represents the 

average value of 25.2 and 22.4x10 -1cm3molecule- ls-1as measured with 

the reference compounds propene and trans-2-butene, respectively. 

d Experimental value from Atkinson et al. (1982). 

e Experimental value from Wallington and Kurylo (1987). 

f Experimental value from Dagaut et al. (1988). 

g Experimental value from Atkinson (1987). 

h,Experimental value from Wallington et al. (1988). 

h Experimental data from Hartmann et al. (1986, 1987) as reported by Atkinson 

(1989). 

1Experimental value from Wallington et al. (1988). The data from Campbell 

and Par'Cinson (1978) was not used since the experimental method was probably 

not valid/Atkinson (1989)]. 

~ Estimated by [Meylan (1990b)] assuming that k(HCOOH **) was 0.400. 

k Atkinson did not develop S/R relationships for carboxylic acids. 

1Experimental value from Dagaut et al. (1988b). The rate data of Zetzsch 

and Stuhl (1981) as reported in Atkinson (1989) is subject to significant 

uncertainties; hence it should not be used [Atkinson (1989)]. 

m Experimental value from Zetzsch and Stuhl (1981) as reported in Atkinson 

(1989). This value is subject to significant uncertainties and must be used 

with extreme caution [Atkinson (1989)]. 

n No experimental value is given in the AOP data base. A value of 

5.5x10 -12 cm3molecule-is-1is given in the document "Estimated Accuracy of 

AOP versus PCFAP. 

o Based on the experimental values of k0U listed in column Experimental/(a). 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-66- 
formate, methyl butyrate). For ethoxyethyl acetate, AOP lists 

the experimental value of kOH with three significant figures 

while Atkinson (1989) and Hartmann et al. (1986, 1987) list it 

with two significant figures. For 2-octanone, AOP lists a value 

of kOg of 10.0 while Wallington and Kurylo (1987) and Atkinson 

(1989) list a value of 11.0. For _q-butyl acetate, AOP does not 

list a value in the data base; from the document "Estimated 

accuracy of AOP versus PCFAP, AOP does list a value of 5.5 for 

this compound. The recommended value by Atkinson (1989) is 5.5*. 

Experimental kOH data listed in Table 16G. are available for 

a few alkyl carboxylic acids --- formic, acetic, propionic, and 

}1- and i-butyric acids as obtained from Atkinson (1989) and the 

literature. The kOH data from Zetzsch and Stuhl (1981) for 

acetic, propionic, and D,-butyric acids had very large 

uncertainties since the vapor pressures of these compounds were 

unknown. Hence, these data should not be used [Atkinson (1989)]. 

The experimental kOH data for acetic, propionic, and i-butyric 

acids were obtained from a single source [Dagaut et al. (1988)]; 

hence, these data should be used with caution until additional 

kOg data are obtained from other researchers to corroborate the 

assignments. 

It should be noted that for the aldehydes, the incorrect 

names are used in the AOP data base. Since, the aldehyde 

functional group can only be at the end of the alkyl chain, there 

is no need to specify its position with a number. 

® 

a-IFC 
s 

~ r 

IV.C.3.b. Evaluation of the Estimated kOH Data 

A comparison of the estimated values of kOH reported by AOP 

with those from HC in Table 16 indicate that they are essentially 

the same except for methyl trifluoroacetate and the carboxylic 

acids. For most of these compounds, the differences are trivial 

and are due to the method of rounding off the third significant 

figure. For methyl trifluoroacetate, the estimated value of kOH 

in AOP is 0.216 in contrast to the estimated value of 0.0518 in 

HC from Leifer. The apparent error is due to the effect of the 

very electrophilic group -CF3on the substituent factor 

F[-OC(0)R]. Leifer (1991a) derived a substitutent factor 

F[-OC(0)CF3 ] = 0.36 (31) 

which gives an estimated value of 0.0518. Therefore, it is 

recommended that the substituent factor listed in 31 be used in 

the AOP computer program and in Table 2. 

There are problems with the S/R relationships of Meylan 

(1990b) for the class of carboxylic acid compounds which will be 

described in the following paragraphs. 

For the alkyl carboxylic acids, Atkinson did not develop S/R 

relationships while Meylan (1990b), in AOP, did develop S/R 

relationships. For these compounds, two reaction pathways were 

postulated by Meylan: H-atom abstraction from an alkyl group and 

H-atom abstraction from the OH group. Therefore, for these two 

reaction pathways, 

=.I-*]= 
R(=0)OH +•OH k(i) = k(la) .R C(=0)OH + HOH (32) 

k(2) = k(-OH) 

RC(=0)OH + •OH RC(=0)O• + HOH (33) 

where R" is an alkyl free radical [i.e., •R I or for formic acid, 

it is •C(=0)OH]. The overall rate of reaction with hydroxyl 

radicals is then 

kOH = k(1) + k(2) = k(la) + k(-OH) (34) 

and Meylan assumed that reaction pathway 32 was the dominant 

pathway [i.e., k(la) > k(-OH)]. Therefore, Meylan used the group 

rate constant k(-OH) = 0.036, derived from the alcohols; and the 

rate constant k(la), for H-atom abstraction from the alkyl group, 

was calculated in the standard manner using the S/R relationship 

of Atkinson. These results were then used in equation 34 to 

calculate kOH. 

For formic acid, Meylan (1990b) assumed that 

k(la) = k[HC(=0)OH ** ] = 0.400 (35) 

so that 

kOg (formic acid, estimated) = 0.436 (36) 

and this result is listed in the fourth column of Table 16. The 

values of kOg (estimated) for the other carboxylic acids are 

calculated in the standard manner in AOP and these results are 

listed in Table 16. The percent error for these compounds, based 

-69- 
on the experimental values of k Og listed in the column 

Experimental/(a), are listed in parentheses in the column 

Estimated/AOP. Inspection of these results indicate that kOH 

(estimated) for acetic acid was very poor (an error of -80%). On 

the other hand, the average percent error for the other 

carboxylic acids was -14 which is excellent. 

Atkinson (1989) reviewed the available kOg data for the 

reaction of OH radicals (or OD radicals) with formic acid (or 

deuteroformic acids) over the temperature range 297-445 K. Based 

on the experimental data of Wine et al. (1986) and Singleton et 

al. (1986) for the reaction of OH radicals with HC(0)OH and 

DC(0)OH and OD radicals with HC(0)OD and DC(0)OD, Atkinson (1989) 

concluded that the major reaction pathway was H- or D-atom 

abstraction from the -OH(or-OD) groups. This contradicts the 

assumption of Meylan (1990b) in AOP; that is, k(-OH) = 0.036 and 

reaction 33 is the minor reaction pathway. Furthermore, as 

stated in Section IV.C.3.a., the experimental kOH data for these 

carboxylic acids are available from a single source and the kOH 

data for acetic, propionic, and butyric acids have large 

uncertainties so that these data must be used with caution. 

Considerably more experimental kOH data are needed for these 

carboxylic acids and for additional compounds in this class 

before reliable S/R relationships can be developed. 

It should be noted that for formic acid, the detailed 

calculation for H-atom abstraction from formic acid is listed in 

-70- 
AOP as k[HCOOH **] = 0.400 (Measured). The molecular structure 

for formic acid is [HC(=0)OH] and not HCOOH. 

IV.C.4. Alcohols, Glycols, Ethers, and Hydroperoxides 

IV.C.4.a. Evaluation of the Experimental kOH Data 

Table 17 summarizes the pertinent experimental k Og data at 

298 K for the reaction of OH radicals with 16 alcohols, 3 

glycols, 26 acyclic ethers, 10 cyclic ethers, and 2 

hydroperoxides as reported in AOP, in Atkinson (1989), and in the 

literature. Inspection of the experimental kO Hdata listed in 

columns 2 and 3 indicate that five compounds have differences. 

The differences in four of these compounds are related to the 

number of significant figures used. Inspection of the original 

literature references and the data in Atkinson (1989) clearly 

indicated that the preferred values are listed in the column 

Experimental/(a). The experimental values for 1-chloro-2,3- 

epoxypropane are different; the preferred value listed in the 

third column represents the average value from the experimental 

kpg data of Zetzsch (1985) and Edney et al. (1986) assuming that 

kOH = 0.55 of Edney. 

IV.C.4.b. Evaluation of the Estimated kpg Data 

Comparison of the estimated values of kpg from AOP and HC 

for the alcohols, glycols, and ethers indicates that they are 

essentially the same. The trivial differences are due to the 

method of rounding off the third significant figure in HC. 

_'. 

-71- 
a 

t ~ 

c 

Table 17. Comparison of the Estimated Values of kOH at 298 K for Alcohols, 

Glycols, Ethers, and Hydroperoxides from the Atmospheric Oxidation 

Computer Proqram (AOP) and from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the Literature Versus the 

Experimental kOH Data in AOP 

10 12k (cm3 molecule- ls-1 ) 

Chemical Class/Chemi al Experimental Estimated 

AOP (a) AOP(%Error)m HC 

A. ALCOHOLS 

Methanol 0.932 0.932* 0.526 0.526 

Ethanol ~, c~ ~-/ ~~°~" 3.27 3. 27* 3.07 3.08 

1-Propanol -7 1- a 3 5.34 5. 34* 4.98 4.99 

2-PropanolX 5.21 5.21* 6.63 6.63 

1-Butanol =7 I5&"`-3 8.3 8. 31b 6.37 6.38 

2-Methyl-2-Propanol&'3 - b.`)" C') 1.12 1.12* 0.593 0.593 

1-Pentanol 10.8 10.8c 7.77 7.77 

2-Pentanol 6v-3V-~9'" + 11.8 11. 8d 10.9 10.9 

3-Pentanol -U P° r 12.2 12.2d 12.9 12.9 

3-Methyl-2-butanol 59$• :75-4 12.4 12.4d 11.0 11.0 

1-Hexanol 12.4 12.4d 9.17 9.17 

2-Hexanol 12.1 12.1d 12.3 12.3 

1-Heptanol /// -:7(}- Co 13.6 13.6d 10.6 10.6 

2-Chloroethanol /0 ~ • o 1.4 1.4 2.07 2.07 

1-Hydroxy-2-propanone 

~ _3 r+ln u ~, 

Cyclopentanol ~jp-'//" ~ 

3.02 

10.7 

3.02e 

10. 7d 

2.31 

12.8 

2.32 

12.7 

B. GLYCOLS 

1, 2-Ethanediol '5'vo" 40 3-0 7.7 7.7 7.42 7.42 

1,2-Propanediol 12.0 12 12.0 11.9 

-72- 
Table 17. Continued 

10 12k (cm3 molecule- ls-1 ) 

Chemical Clas /Chemical Experimental Estimated 

AOP (a) AOP($Error)m HC 

C. ACYCLIC ETHERS 

Dimethyl ether 2.98 2.98* 1.76 1.76 

Diethyl ether ~p-ac7~-~. 13.3 13.3* 11.5 11.5 

Di-n-Propyl ether ///-y3-3 17.2 17 . 2* 21.1 21.1 

Methyl-jt-butyl ether 1(p3q-oLf-4 2.83 2.83* 2.82 2.82 

Methy 1-n-buty 1 ether G,;) S 16.4 16.4d 13.6 13.6 

Ethyl-n-butyl ether C~ ~- ~~- ~ 18.1 18.1f 18.5 18.5 

Ethyl-jt-butyl ether ~~ ~„y~ 3 6.9 6.88f 7.70 7.20 

Methyl-jt-amyl ether 99 4- O5--g 7.91 7.91d 6.13 6.13 

Di-n-butyl ether /j~a. -go- 22.4 22.4f 25.5 25.5 

D i-.i-buty l ether Gae^- ~ST " ~' 26.0 26.Og 30.4 30.4 

Di-n-pentyl ether &)1/ 2)- &!:15-- '::~ 34.7 34 .7d 28.2 28.2 

1,1-Dimethoxy ethane ~3'-/- /S(o 8.89 8. 89e 13.1 13.1 

Diethoxymethane M&V-VI5 °3 16.8 16.8e 16.6 16.6 

1,2 -D imethoxypropane 7q-jg -$5-O 14.3 14.3e 22.9 22.9 

2, 2-Dimethoxypropane -71--76 -9 3.92 3. 92e 3.05 3.05 

2, 2-Diethoxypropane /.) 6 - aq- ) 11.7 11.7e 12.8 12.8 

2-Methoxyethyl ether -,~' -=1g 17.5 17.5e 28.1 28.1 

1//-9w-Co t ~ kiyv ~3 

1, 1, 3 -Tr imethoxypropane ~-U 19.2 19.2e 28.5 28.5 

2-Ethoxyethyl etherX 26.8 26.8e 37.9 37.8 

Methoxy acetone,~~ I- fi - /`~ --'~ 6.77 6.77e 4.87 4.87 

2-Methoxy ethanol 109-9'&- q 12.5 12.5e 11.2 11.2 

2-Ethoxy ethanol //~ -~O- ~ 15.4 15.4h 16.1 16.1 

3-Ethoxy-l-propanol 1I1- j~)--3 22.0 22.0e 20.9 20.9 

3-Methoxy-l-butanol ~~~~-1~C3_ 3 23.6 23.6e 20.6 20.6 

2-Butoxy ethanol ///- f6 18.6 18.6h 23.0 23.0 

1 j 

-73- 
S ~ 

Table 17. Continued 

10 12k (cm3 molecule-is-1 ) 

Chemical Class/Chemica Experimental Estimated 

AOP (a) AOP($Error)m HC 

2-Hydroxyethyl ether %//-14,- 6 

(Dihydroxyethyl ether) 30.0 30 20.6 20.6 

D. CYCLIC ETHERS 

Ethylene oxide 0.076 0.076* 0.224 0.224 

1,2 -Epoxypropane (propylene 

oxide) SS(o-y 0.052 0.52* 0.543 0.543 

1-2 -Epoxy butane (1 ~ 2- - 7- 

--3 Z~ Butylene oxide) ry~~ ~ ~ 2.1 2.1 1.69 1.69 

1-Chloro-2, 3-e o p xypropane 0.44 0.50 i 0.662 0.662 

Trimethylene oxide5,03 -.30"0 10.3 10.3e 3.73 3.73 

Tetrahydrofuran 169-9 y- 9 16.1 16 .1* 18.3 18.3 

1, 3-Dioxane stj ,j ~aa -lo 9.15 9.15e 22.1 22.1 

1,4-Dioxane jo?,3- y/- ~ 10.9 10.9e 26.4 26.4 

1,3,5-Trioxane 6.2 6.2i 15.3 15.3 

Oxepane (Hexamethylene oxide) 15.4 15.4e 25.7 2.57 

5%9, -- 90 .s" 

E. ALKYL HYDROPEROXIDES 

Methyl hydroperoxide 3o31- Y3 - 0 5.54 5.54* 7.24(+31) (1) 

-t-Butyl hydroperoxide 941- 2& -8 3.0 3.0k 1.98(-34) (1) 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Wallington and Kurylo (1987a). The data from 

Campbell et al. (1976) was not used since the validity of the experimental 

method is questionable [Atkinson (1989)]. 

c Experimental value from Wallington and Kurylo (1987a). 

d Experimental value from Wallington et al. (1988b). 

-74- 
1 • 

1 

y ~ 

Table 17. continued 

e Experimental value from Dagaut et al. (1988a). 

f Average value from the experimental data of Wallington et al. (1988b) and 

Bennet and Kerr (1989). 

g Experimental value from Bennett and Kerr (1989). 

h Experimental value from the experimental data of Hartmann et al. (1987) and 

, Dagaut et al. (1988a). 

1 Average value from the experimental data of Zetzsch (1980) and Edney et al. 

(1986) assuming kOH = 0.55x10' 12 cm3 molecule- is-1 of Edney. 

7 Extropolated from the experimental data of Zabernick et al. (1988). 

k Experimental value from Anastasi et al. (1978). 

1 Atkinson did not develop S/R relationships for alkyl hydroperoxides. 

m Based on the experimental values of kpU listed in column Experimental/(a). 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

/ 

-75- 
.~ 

~ 3 

There are, however, problems with the S/R relationships for 

the alkyl hydroperoxides in AOP which will be described below. 

For the alkyl peroxides [RCOOH], Atkinson did not develop 

S/R relationships while Meylan (1990b), based on the experimental 

kOg data of inethyl and _t-butyl hydroperoxide, did develop S/R 

relationships. For alkyl peroxides, two reaction pathways were 

postulated by Meylan: H-atom abstraction from the alkyl group and 

H-atom abstraction from the hydroperoxy groups. Therefore, 

_ 

RCOOH + •OH 

(1) (la) 

.RI

COOH + HOH (37) 

k(2) = k(-OH) 

RCOOH + ~ OH ROO• + HOH (38) 

where R is an alkyl group and •R' is an alkyl free radical group. 

The overall reaction with OH radicals is then 

kOH = k(1) + k(2) = k(la) + k(-OH) (39) 

and reaction pathway 37 was considered by Meylan (1990b) to be 

the dominant reaction pathway. Therefore, Meylan assumed that 

k(-OH) = 0.036 and 

F(-0-0- ** ) = 50 (40) 

and k(la) and kOH were calculated in the standard manner. For 

methyl and t-butylhydroperoxides, the estimated values from AOP 

were 7.24 and 1.98, respectively. The percent error for these 

two compounds, based on the experimental values listed in column 

Experimental/(a), were +31 and -34, respectively, and these 

-76- 
s• 

~ i 

results were very good. However, these results, and the S/R 

relationships of Meylan must be evaluated very carefully in the 

light of the experimental kOg data as described in the following 

paragraphs. 

Atkinson (1989) analyzed the experimental rate data of 

Vaghjiani and Ravishankara (1989) and Niki et al. (1983) for 

methyl hydroperoxide. The most comprehensive study is that of 

Vaghjiani and Ravishankara (1989) who studied the rates of 

reaction of 160H, 18 0H, and 160D radicals with CH300H and 160D 

radicals with CH300D. Based on an analysis of all the 

experimental data, the mechanism involves two reaction pathways; 

H-atom abstraction from the CH3 group and from the OH group. 

Therefore, 

CH300H + •OH 

k(2) = k(-OH) 

CH300• + HOH (41) 

k(1) = k(la) 

CH300H + •OH •CH2O0H + HOH (42) 

with the •CH2O0H radical rapidly decomposing to give hydroxyl 

radicals and formaldehyde 

•CH2=0 O-H P -+ CH Ra 2 =0 + •OH (43) 

The overall rate, from reactions 41 and 42, is 

kOH= k(1) + k(2) = k(la) + k (-OH) (44) 

-77- 
.. 

2 2 

Relative rate studies gives k OH[= k(la) + k(-OH)] while 

flash photolysis or laser photolysis experiments, which measure 

the disappearance of OH radicals, gives only the rate constant 

k(-OH) assuming that OH radical regenerated contains the same 

oxygen isotope as the reactant OH radical. Therefore, the 

reaction of the 160H radical with CH30 160H (or 160D radical with 

CH30160D) gives the rate constant k(-OH). Furthermore, reaction 

of OD radicals with CH300H yields the overall rate constant 

kOH[= k(la) + k(-OH)] for the OD radical reaction. 

Atkinson (1989) carrzed out a unit-weighted least-squares 

analysis of the experimental data of Vaghjiani and Ravishankara 

(1989) for the reaction of 180H and OD radical with CH300H over 

the temperature range 203-348K. Based on these data, Atkinson 

recommended the value of 

k(-OH) = 3.73 (45) 

at 298 K(in the units 10 -12 cm3 molecule- is-1 ); from the 

experimental data involving 180H and OD radicals over the 

temperature range 223-423 K, Atkinson recommended a value of 

kOH = 5.54 (46) 

at 298 K(in the units 10 -12 cm3molecule- is-1 ). Hence, 

k(la) = 1.81 (47) 

and H-atom abstraction from the OH radical in methyl 

hydroperoxide is the major reaction pathway. 

-78- 
.. 

.• ~ 

For t-butyl hydroperoxide, Atkinson (1989) indicated that 

because the C-H bonds in the CH 3group are stronger than the O-H 

bond, the reaction is expected to proceed principally via H-atom 

abstraction from the weaker OH bond (reaction pathway 41) and 

this result is consistent with the magnitude of kOH determined 

experimentally by Anastasi et al. (1978). 

Therefore, all the data presented by Atkinson (1989) 

contradicts the S/R relationships of Meylan (1990b) for the alkyl 

hydroperoxides. Considerably more experimental rate data is 

needed for additional alkyl hydroperoxides to develop S/R 

relationships for this class of compounds. 

IV.C.5. Alkyl Nitrates and Nitriles 

IV.C.5.a. Evaluation of the Experimental kOH Data 

Table 18 summarizes the pertinent experimental kOH data at 

298 K for acyclic and cyclic alkyl nitrates and acyclic alkyl 

nitriles as reported in AOP, in Atkinson (1989), and in the 

literature. Inspection of the kOH data in columns 2 and 3 

indicate that the experimental values for all acyclic and cyclic 

nitrates are identical. However, for the nitriles, there are 

differences. For acetonitrile, the correct value of kOH is 

0.0214* as recommended by Atkinson (1989) and the correct value 

for propionitrile is 0.194 as given by Harris et al. (1981) and 

Atkinson (1989). 

-79- 
; 

Table 18. Comparison of the 

Nitrates and Alkyl 

Program (AOP) and 

kOHData Reported 

in AOP 

Estimated Values of kpg at 298 K for Alkyl , 

Nitriles from the Atmospheric Oxidation Computer 

from a Hand Calculation (HC) and the Experimental 

in the Literature Versus the Experimental k OHData 

10 12k (cm3molecule'ls' 1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

A. ACYCLIC NITRATES 

Methyl nitrate -~`~ S' ~$' ~ 0.034 0.034b 0.0259 0.0259 

Ethyl nitrate(~ = sg- ~ 0. 49c 0. 49c 0.194 0.194 

1-Propyl nitrate /3 -A/ 0.67 0.67d 0.632 0.632 

2-Propyl nitrate 0.41 0.41e 0.416 0.416 

1-Butyl nitrate n~~Y~N r~~~~~- 1.78 1.78e 1.79 1.79 

2-Butyl nitrate~~ yH~>tiu.3 0.92 0. 92e 0.905 0.905 

2-Pentyl nitrate,, F 1.85 1.85f 2.06 2.06 

3-Pentyl nitrate/ 1.12 1.12f 1.42 1.42 

2-Methyl-3-butyl nitratex , 1.72 1.729 1.39 1.39 

2,2-Dimethyl-l-propyl nitratey 0.85 0.859 0.752 0.752 

2-Hexyl nitrate ~ n-N~-xyLti /T;~:j~ 3.17 3.17f 3.45 3.45 20633 - i/- s3 

3-Hexyl nitrate ~ 2.70 2.70f 2.58 2.58 

2-Methyl-2-pentyl nitrate,; 1.72 1.729 1.68 1.68 

3-Methyl-2-pentyl nitrate/` 3.02 3.029 2.63 2.63 

3-Heptyl nitrate ;" 3.69 3.699 3.97 3.97 

~3-Octyl nitrate - 39 - 3.88 3. 88 f 5.37 5.37 

cBti~~Nc~ 3 

B. CYCLIC NITRATES 

Cyclohexyl nitrate 210$ -(pU-q 3.30 3.309 5.38 5.38 

C. ALKYL NITRILES 

Acetonitrile -7~~ 05°8 0.021 0.0214* 0.0202 0.0202 

Propionitrile /p ~-- /a -Q 0.19 0.194h 0.189 0.189 

-80- 
~ , , ~ •4'- .. 

1i 

4.i 

Table 18. continued 

a Experimental values from Atkinson (1989) and the literature. 

b Atkinson ~ 1987, 1989) reported a value of 0.034x10 -12and 

0.38x10-1cm3 molecule- ls-1from Gaffney et al. (1986) and Kerr and Stocker 

(1986), respectively. Atkinson (1987) used the value of 0.034 x 10 -12since 

it was more consistent with the entire set of kOH data used to develop the 

S/R relationships and the value from Kerr and Stocker was systematically too 

high. Atkinson (1989) also tentatively preferred the value of Gaffney 

et al. (1986) since the value of Kerr and Stocker was too high. 

c The experimental data of Kerr and Stocker (1986) was considered too high 

and was not considered to be valid [Atkinson (1987, 1989)]. 

d This value of kOH represents the average value from the experimental data of 

Kerr and Stocker (1986) and Atkinson and Aschmann (1989a). 

e Experimental value from Atkinson and Aschmann (1989a). 

f Experimental value from Atkinson et al. (1982a). 

g Experimental value from Atkinson et al. (1984b). 

h Experimental value from Harris et al. (1981). 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-8i- 
.. 

. ~ 

IV.C.5.b. Evaluation of the Estimated k OHData 

Inspection of the estimated values for the nitrates and 

nitriles in columns 4 and 5 indicate that both AOP and HC have 

exactly the same kOHdata. 

IV.C.6. Nitroalkanes 

IV.C.6.a. Evaluation of the Experimental kOHData 

Table 19.A. summarizes the pertinent experimental kOH data 

at 298 K for nitroalkanes as reported in Atkinson (1989), in 

AOP, and in the literature. For nitromethane, AOP lists a range 

of experimental values for kOH. Atkinson (1989) evaluated the 

existing experimental kOH data for nitromethane and indicated 

that the data of Zabarnick et al. (1988) is preferred. Atkinson 

carried out a unit-weighted least squares analysis of the 

Zabarnick data using the equation 

kOH = CT2 exp(-D/T) (48) 

where C and D are constants and T is the absolute temperature in 

K and found that 

kOH = 5.6 x 10 -19T2 exp(-360/T) cm 3 molecule- is-1 (49) 

over the temperature range 299-671 K. At 298 K, equation 49 

gives 

kOH = 0.0149 x 10 -12 cm3 molecule - is-1 (50) 

-82- 
ar 

~ t 

Table 19. Comparison of the Estimated Values of kpg at 298 K for 

Nitroalkanes and Alkyl Nitrites from the Atmospheric Oxidation 

Computer Program (AOP) and from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the Literature Versus the 

Experiment kOHData in AOP 

10 12k (cm3 molecule- is-1 ) 

Chemical Class/Chemica Experimental Estimated 

AOP (a) AOP($Error)j HC 

A. NITROALKANES 

Nitromethane 75-5-a S (0.016-0.16) 0.0149b . 0.0259(+74) (c) 

Nitroethane 79-2 ~f3 0.15 0.15d 0.194(+29) (c) 

1-Nitropropane /og-- 03- 2 0.24 0. 34d 0. 632 (+86) (c) 

1-Nitrobutane 6.7 ~-- 1.45 1. 45e 1. 79 (+23 ) (c) 

1-Nitropentane6a$- O5'7 3.30 3.30d 3.18(-4) (c) 

B. ALKYL NITRITES 

Methyl nitrite (0.12-1.08)? (0.12-1.09)f 0.288 (---) (c) 

Ethyl nitrite /o9- ~S`~~ 1.75? 1.779 2. 32 (+31) (c) 

1-Propyl nitrite 5-Y3 -( 1- 9 2.38? 2.36h 6.12(+160) (c) 

1-Butyl nitrite.,jy}--/& -/ (2.31-5.2)? 5.02h 8.29(+65) (c) 

2-Butyl nitrite 9o?V- 5. 93? 5. 97 1 6. 17 (+3 ) (c) 

2-Methyl-l-propyl nitriteX 5.31? 5.35 1 10.8(+101) (c) 

2-Methyl-2-propyl nitrite~ 1.40? 1.41 1 1.94(+38) (c) 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Zabarnick et al. (1988) which represents the 

preferred value by Atkinson (1989). 

c Could not be calculated by Leifer since the S/R relationships and 

substituent factors were unknown. 

-83- 
M14 

Table 19A. continued 

d Experimental value from Nielsen et al. (1988). Atkinson (1989) 

tentativelv accepted this data since "The nitroalkanes are expected to 

photolyze [Taylor et al. (1990)) and it is not clear whether photolysis 

occurred under the experimental conditions of the relative rate study of 

Nielsen et al. (1988) or whether or not photolysis (if it occurred) was 

taken into account". More experimental kpH data are needed under controlled 

laboratory conditions to eliminate photolysis. 

e The average value from the data of Atkinson (1989) and Nielsen et al. 

(1988). See footnote (d) above relative to the experimental value from 

Nielsen et al. (1988). 

f Range in experimental kpH data as obtained from Atkinson (1989) and the 

literature in the units 10 -12 cm3molecule- ls-1 : 0.12 relative to dimethyl 

ether and 0.21 relative to n-hexane [Tuazon et al. (1983)]; 1.00 [Baulch 

et al. (1985); 1.09 [Audley et al. (1982)j; and the data of Campbell and 

Goodman (1975) was omitted since there were fundamental problems associated 

with the relative method used [Atkinson (1989)]. 

g Experimental value from Audley et al. (1982) and Atkinson (1989). 

h Average value from the experimental data of Audley et al. (1982) and Baulch 

et al. (1985) is obtained from Atkinson (1989). 

i Experimental value from Audley et al. (1982). 

~ Percent error relative to the experimental values listed in column 

Experimental/(a). 

-84- 
and this is the value listed in column three of Table 19.A. and 

is the preferred (or recommended) value by Atkinson. For the 

remaininq nitroalkanes, only for 1-nitropropane is there a 

discrepancy in the kOH data in columns 2 and 3. The correct 

experimental value for 1 -nitropropane is tentatively 0. 34 as 

obtained from Nielsen et al. (1988) and Atkinson (1989). 

Some comments must be made about the validity of the 

experimental kpg data for nitroethane, 1-nitropropane, 

1-nitrobutane and 1-nitropentane. For nitroethane, 

1-nitropropane, and 1-nitropentane, the experimental data were 

obtained from Nielsen et al. (1988) and Atkinson (1989) while the 

experimental data for 1-nitrobutane was obtained from Atkinson 

and Aschmann (1989) and Nielsen et al. (1988). Atkinson (1989) 

critically evaluated the experimental k OH data of Nielsen and 

stated that "The nitroalkanes are expected to photolyze [Taylor 

et al. (1980)J and it is not clear whether photolysis occurred 

under the experimental conditions of the relative rate study of 

Nielsen et al. (1988) or whether or not photolysis (if it 

occurred) was taken into account." As a result, Atkinson (1989) 

indicated that the data listed in the column Experimental/(a) for 

nitroethane, 1-nitropropane, and 1-nitropentane from Nielsen are 

only tentativelv preferred and, therefore, must be used with 

extreme caution. 

IV.C.6.b. Evaluation of the Estimated k OH Data 

Leifer did not have available S/R relationships for the 

nitroalkanes from Atkinson; hence, no entries appear in Table 

~ 

s ■ 

.;' 

-85- 
:l 

~ 

19.A., column Estimated/HC. Meylan (1990b) did have S/R 

relationships available for these compounds from Atkinson 

(unpublished results). For this class of compounds (RNO2), 

Atkinson must have postulated that hydroxyl radicals can only 

react by abstracting a hydrogen from the C-H groups in R and the 

substituent factors were 

F(-NO2) = 0.18 (51) 

F(-CH2NO2) = 0.30 (52) 

In addition, Meylan (1990b) gave the substituents >CHNO2 and 

> CNO2 the same F values as for the substituent -CH2NO2 listed in 

equation 52. Thus, the assumed values for these two substitutes 

(designated **) are then 

F(>CHNO2 ** ) = F(> CNO2 ** ) = 0.30 (53) 

Using the above substituent factors, AOP estimated kOg for the 

five nitroalkanes listed in Table 19.A. and these results are 

listed in the column Estimated/AOP. The percent error, relative 

to the experimental kOHdata in column 3, are listed in 

parentheses adjacent to the estimated value from AOP. Inspection 

of these data clearly indicate that the results for nitromethane 

and 1-nitropropane are very poor. In addition, the average 

percent error ranged from +53 to -4. Therefore, in order to 

develop better substituent factors for the nitroalkanes, more 

experimental kOHdata are needed for these five compounds and 

additional nitro compounds under carefully controlled laboratory 

i~ 

-86- 
conditions to eliminate direct photolysis. Until this work is 

completed, the substituent factors and estimated values of kOH 

for the nitroalkanes must be used with extreme caution, or, 

better, delete them from AOP. 

IV.C.7. Alkyl Nitrites 

IV.C.7.a. Evaluation of the Experimental kOH Data 

Table 19.B. summarizes the pertinent experimental kOH data 

at 298 K for the alkyl nitrites (RONO) as obtained from AOP, from 

Atkinson (1989), and from the literature. For these compounds, 

the experimental kOH.data from AOP have question marks 

immediately after the numbers to indicate that the data are 

questionable. For the experimental data for methyl nitrite, 

several values are available from the literature. Thus, the 

experimental kOH data in columns 2 and 3 list essentially the 

same range of values. For 1-butyl nitrite, AOP lists a range of 

values while the column Experimental/(a) lists the average value 

from the experimental data of Baulch et al. (1985) and Audley et 

al. (1982). For the other alkyl nitrates there are minor 

differences listed in columns 2 and 3. The values listed in the 

third column, as obtained from the literature and Atkinson 

(1989), appear to be the correct values. 

It should noted that for the compound CH3CH(CH3)CH2ON0, AOP 

lists the name 3-methyl-l-propyl nitrite which is incorrect. The 

correct name is 2-methyl-l-propyl nitrite. 

i . 

> ~ 

-87- 
a 

"L 

a 

IV.C.7.b. Evaluation of the Estimated k OHData 

Leifer did not have available S/R relationships from 

Atkinson for the alkyl nitrites; hence, no entries appear in the 

column Estimated/HC. However, Meylan (1990b) did develop S/R 

relationships for this class of compounds (RONO) by assuming that 

the only reaction pathway is H-atom abstraction from the C-H 

groups in R. Based on the available experimental kOH data, 

Meylan assumed that for the nitrites 

F(-O-N = ** ) = 2.00 (54) 

Furthermore, for these compounds, where appropriate, Meylan used 

the substituent factor F(-CH2-O-) from Table 2. 

Using the above substituent factors, AOP calculated kOH; and 

these values are listed in Table 19.B. along with the percent 

error (in brackets adjacent to the estimated values). From an 

inspection of the percent error data, it is clear that the 

results are generally very poor; 1-propyl nitrite and 2-methyl-lpropyl nitrite had percent errors greater than +100 while 1- 

butylnitrite had a percent error of +65. These results are not 

surprising since Atkinson (1989) Stated "Until the kinetics of OH 

radicals with alkyl nitrites are fully understood and product 

studies carried out, the reaction mechanisms remain uncertain. 

These may proceed via H-atom abstraction from the C-H bonds ---- 

and this is expected to be the major, if not the only, reaction 

pathway ---". Therefore, it is apparent that more reliable kOH 

data and product data are needed for the alkyl nitrites listed in 

-88- 
~ 

a~ 

Table 19.B. and for other alkyl nitrites in order to develop more 

reliable S/R relationships. 

IV.D. Addition of Hydroxyl Radicals to Alkenes, Conjugated 

Dialkenes, Alkynes, and 1,2-Dialkenes* 

IV.D.1. Unsubstituted Alkenes 

IV.D.i.a. Evaluation of the Experimental kOH Data 

Table 20 summarizes the pertinent experimental kOH data at 

298 K for the reaction of OH radicals with unsubstituted alkenes 

as reported in AOP, in Atkinson (1989), and in the literature. A 

careful inspection of the experimental kO Hdata reported in the 

columns Experimental/AOP and Experimental/(a) indicates that, in 

general, they are the same; there are, however, some differences. 

For a few chemicals, AOP lists kOH to 4 significant figures while 

Experimental/(a) reports kOg to 3 significant figures. At best, 

the experimental kOH data is good to 3 significant figures. For 

example, for 2,3-dimethyl-2-butene, the experimental kOg data 

reported in the literature is only given to 3 significant and 

Atkinson (1989) recommended a value of 110* while AOP lists a 

value of 110.0. For the other chemicals with differences, 

Experimental/(a) lists an average value from the literature while 

AOP selects one set. Unless there is good reason to disregard 

specific sets of data, it is best to list an average value from 

all the data sets rather than the value from only one set. 

It should be noted that AOP does not list an experimental 

value for 43 - carene in column 2; however, a value is listed in 

the document "Estimation Accuracy of AOP versus PCFAP" (Meylan 

-89- 
~ 

Table 20. Comparison of the Estimated Values of k OH at 298 K for Unsubstituted 

Alkenes from the Atmospheric Oxidation Computer Program (AOP) a,rnd, 

from a Hand Calculation (HC) and the Experimental k QHData Reperted 

in the Literature Versus the Experimental kOH Data in AOP 

10 12k (cm3 molecule- ls -1 ) 

Chemical Class/Chemica Experimental Estimated 

AOP (a) AOP HC 

A. ACYCLIC ALKENES 

Ethene (Ethylene) 3 ~- g,5" l 8.52 8.52* 8.5200q (r) 

Propene (Propylene) //j -O 7°/ 26.3 26.3* 26.4 26.4 

1-Butene /bCn- 9$- ~'; 31.4 31.4* 27.3 27.3 

cis-2 -Butene 56.4 56.4* 56.4 56.4 

trans-2-Butene (a~-~~/ ~ cy/`g 64.0 64.0* 64.0 64.0 

2-Methylpropene /iS-/i- ~~: yi-IF 51.4 51. 4* 51.7 51.7 

1-Pentene /oy- !o -f'/ 31.4 31. 4* 28.6 28.6 

cis-2-Pentene &;2 a0-3 65.4 65.7b 57.3 57.3 

trans-2-Pentene (~lo - 04

/'ff' 66.9 66.9c 64.9 64.9 

2-Methyl-2-butene S13 - 35 'y 86.9 86.9* 87.3 87.3 

2-Methyl-1-butene j`(~~ -~~ ~ 2 60.7 60. 6d 52.6 52.6 

3-Methyl-l-butene ~3~~ " ~ 31.8 31.8* 28.5 28.5 

1-Hexene 59,~ • 1//- 4p 37.535.2e 30.0 30.0 

2-Methyl-l-pentene Wo Z ~ -29 -1 62.6 62.6f 53.9 53.9 

2-Methyl-2-pentene &dY - 2 ~ -- ~ 88.8 89.19 88.2 88.2 

trans-4-Methyl-2-pentene6Y`/° ~X- -0 60.8 60.5f 66.0 66.0 

2, 3-Dimethyl-2-buteneS6,3-79- ) 110.0 110* ill ill 

3,3-Dimethyl-l-butene-'b-8•3F --~ 28.4 28.5h 26.9 26.9 

1-Heptene ,5W- ~(,- ~- 40.5 38. 3 1 31.4 31.4 

2,3-Dimethyl-2-pentene 5?y-3~S 108.0 103j 111 111 

trans-4,4-Dimethyl-2-pentene 1e90-ou-i( 

1,4-Pentadiene 3 l/- 93 -5 

54.5 

53.3 

54.5f 

53.3c 

64.4 

53.4 

64.4 

53.4 

trans -1,4-Hexadiene -0 90.3 90.6c 91.0 91.0 

1, 5-Hexadiene ~~a - L f~ -~- 62.1 62 . Oc 54.8 54.8 

~ 
~ 

~= 

Table 20. Continued 

10 12k (cm3 molecule- ls -1 ) 

Chemical Class/ emical Experimental Estimated 

AOP (a) AOP HC 

2-Methyl-1,4-pentadiene-IA - 30"q 78.8 78.8c 78.7 78.7 

2-Methyl-1,5-hexadiene ~~~~ 96.1 96. 1c 80.0 80.0 

- 

y~~ -'~-~' ~, 

2,5-D~ntethyl-1,5-hexadiene 120.0 120c 105 105 

B. CYCLIC ALKENES 

Cyclopentene /~a - ~ bJ°Q 67.3 65.5k 58.9 58.9 

Cyclohexene //p- 8 3r-g 67.7 67.7* 61.1 61.1 

1, 4-Cyclohexadiene 29797-09-9 99.4 99.5 1 114 114 

Cycloheptene &p.28-qa-2, 74.4 74.4m 62.4 62.5 

1-Methylcyclohexene 94.4 94.4n 92.0 92.0 

Bicyclo [2.2.1]-2-hepteneyy5 td- ~ 49.3 49.3m 62.7 62.7 c?14(3v 

Bicyclo[2.2.1]-2,5-heptadtene 120.0 120m 116 116 

Bicyclo[2.2.2]-2-octene 40.8 40.8m 67.8 67.8 

a-Pinene S0R 5G- Es'' 931- G4-4& 53.7 53 . 7* 89.5 89.5 

O-Pinene / a-7 -9f- 3 78.9 78 . 9* 54.2 54.1 

d-Limonene -~~ -5~'~ 171.0 160n 145 145 

03 -Carene ~~~/~,~ - ~~~9 (p) 87.80 87.6 87.6 

y-Terpinene 177.0 177 0 178 178 

a Experimental values from Atkinson (1989) and the literature. 

b Average value from the data of Ohta (1984) and Wu et al. (1976). 

c Experimental value from Ohta (1983) and Atkinson (1989). 

d Average value from the data of Ohta (1984) and Wu et al. (1976). The 

experimental value of kOH of Morris and Niki (1971) was considered to be too 

high and was discounted when making recommendations for other alkenes (e.g., 

for 1-pentene) by Atkinson (1989). 

e Average value from the experimental data of Wu et al. (1976) and Atkinson 

and Aschmann (1984). 

f Experimental value from Ohta (1984) and Atkinson (1989). 

g Average value of the relative rate data of Ohta (1984) using 2-methyl-2- 

butene andcis-2-pentene as reference compounds. 

-91- 
~ 

. ;, 

h Experimental value from Wu et al. (1976) and Atkinson (1989). 

1Average value of the experimental data of Darnall et al. (1976) and 

, Atkinson and Aschmann (1984). 

7 Average value of the relative rate data of Ohta (1984) using 2-methyl-2- 

butene and 2,3-dimethyl-2-butene as reference compounds. 

k Average value from the experimental data of Atkinson, Aschmann, and Carter 

.(1983) and the relative rate data of Rogers (1989) with cyclohexene as the 

reference compound. 

1Average value from the experimental data of Atkinson, Aschmann, and Carter 

(1983) and Ohta (1983). 

m Experimental value from Atkinson Aschmann, Carter (1983). 

n Experimental value from Darnall et al. (1976). 

o Experimental value from Atkinson, Aschmann, Pitts (1986). 

p No experimental value is qiven in the AOP database. An experimental value 

of 87.8x10-12 cm3molecule- Is-1is given in the document estimation 

accuracy of AOP versus PCFAP. 

q Estimated value is the experimental value. 

r Cannot be estimated by the S/R relationships of Atkinson. 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-92- 
i 

(1990b)]. The value of 87.8 should be listed in the AOP 

database. 

IV.D.l.b. Evaluation of the Estimated kOHData 

Comparison of the estimated kpH data in columns 4 and 5 

indicates that, in general, they are the same; there are, 

however, a few differences. For ethene, AOP lists a estimated 

value of 8.5200 in the summary table which corresponds to the 

experimental value while HC does not list a value; kpHcannot be 

estimated by the S/R relationships of Atkinson. Furthermore, AOP 

lists the estimated value to five significant figures whYch is 

incorrect since the recommended experimental value by Atkinson 

(1989) is 8.52* which only has three significant figures. 

For OH addition to olefinic bonds, the detailed calculations 

show an inconsistency. From the mathematical synopsis of the S/R 

relationships of Atkinson (equation 15), substituent factors 

attached to the olefinic group can influence kadd,nar (or kd in 

Meylan's notation), Table 8; therefore, for consistency in 

calculating the rate constant for this reaction pathway, the term 

C(R) should be used, even though C(R) = 1.00. For example, for 

1-pentene, OH addition to the olefinic group should be 

kadd,nar = kos (CH2=CHR)[C(R)] = 26.3(1.00) 

kadd,nar = 26.3 

(55) 

For 2-methyl-2-pentene, 

kadd,nar = ko s (R1R2C=CHR3)[C(R1)C(R2)C(R3)] 

-93- 
kadd,nar - kos (RiR2C=CHR3)(1.00)(1.00)(1.00) 

kadd,nar = 86•9 (56) 

This comment is also applicable to the compounds listed in Table 

22 for the conjugated dienes, and in Table 23 for the allenes and 

alkynes. 

For C-H abstraction from the olefinic group (e.g., =C-H), 

the detailed calculations should include this pathway, even 

though it is zero [i.e., k(1, UNS CH) = OJ. This comment, as 

well as the above comment, also applies to the other classes of 

compounds discussed in Section IV.D. 

IV.D.2. Substituted Alkenes 

IV.D.2.a. Evaluation of the Experimental kOH Data 

Table 21 summarizes the pertinent experimental kOH data for 

the reaction of OH radicals with substituted alkenes as reported 

in Atkinson (1989), in AOP, and in the literature. A comparison 

of the experimental kOH data listed in columns 2 and 3 indicate 

that, in general, they are the same; there are, however, some 

differences. For six compounds [i.e., 2-(chloromethyl)-3-chloro1-propene, trans-2-butenal, and the four ketenes, no experimental 

kOHvalues are listed in AOP; however, values are reported in the 

document "Estimation Accuracy of AOP versus PCFAP "[Meylan 

(1990b)]. The appropriate values should be listed in AOP. For 

acrylonitrile, AOP lists an experimental value of 4.0 while the 

correct value should be 4.1, the average value of the 

~ 

-94- 
;► .. 

Table 21. Comparison of the Estimated Values of kp Hat 298 K for Substituted 

Alkenes from the Atmospheric Oxidation Computer Program (AOP) and 

From a Hand Calculation (HC) and the Experimental k QHData Reported 

in the Literature Versus the Experimental k OH Data in AOP 

10 12k (cm3 molecule- ls-1 ) 

Chemical Class/Cheic 1 Experimental Estimated 

AOP (a) AOP HC 

A. Haloalkenes. 

Vinyl f luoride :75`-0 2-'r 5.56 5. 56b 10.5 10.5 

Vinyl chloride =~S-D/- 4/ 6.60 6.60b 5.26 5.26 

Vinyl bromides9 ,3-. Ga- Z„ 6.81 6.81b 6.84 6.84 

1, 1 -D if luoroethene - 7 2.1 2. ic 8.22 8.22 

g"-1, 2-Dichloroethene /&30 -73-9 2.38 2. 38d 2.24 2.24 

trans-1,2-Dichloroethene/6, 30 - 3g-O 1.80 1.80d 2.55 2.55 

Trichloroethene 79 ...0/ _(v 

(Trichloroethylene) 2.36 2.36* 0.695 0.695 

Tetrachloroethene 

(Tetrachloroethylene) x 0.167 0.167* 0.176 0.176 

3-Chloro-l-propene /o- ~- vs°- j 

(3-Chloropropylene) 17.0 17* 20.3 20.3 

cis-1,3-Dichloro-l-propene 8.41 8.41d 8.85 8.85 

10(j61-01 s 

trans- 1, 3 -Dichlor ~1~ ~~ op~e~ne~ 14.3 14.3d 10.0 10.0 

2-(Chloromethyl)-3-chloro1-propene (e) 33.5d 30.3 

B. a,B-UNSATURATED CARBONYLS 

Acrolein (2-Propenal)/04-0 Z-$ 19.9 19.9* 22.9 22.9 

trans-Crotonaldehyde(trans2-Butenal) /a3-713- 9 (e) 36* 32.8 32.8 

Methacrolein(2-Methyl-2- 

propenal) 33.5 33.5* 29.6 29.6 

-95- 
6 

.Y 

~ ~~u 

.~ 

E~• 

f 

~ A 

Table 21. Continued 

10 12 k (cm3 molecule- ls-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

Methyl vinyl ketone ~~W ~~- ~ 18.8 18.8* 24.0 24.0 

Ketene //& 3 ( e) 17 3 f 51.4 51.4 

Methyl keteneX (e) 709 87.0 87.0 

Ethyl ketene ~ (e) 118f 87.9 87.9 

Dimethyl ketene k (e) 107f 110 110 

cis-3-Hexene-2, 5-dione 63.1 63.1h 46.7 46.7 

a 

trans -3-Hexene-2,5-dione 53.1 53.1h 53.0 53.0 _ 9 

C. NITRILOALKENES 

Acrylonitrile (Cyanoethene) 4.0 4.1 1 3.95 3.95 

/0 ?-- 13 - / 

D. ALKOXY ALKENES 

Methyl vinyl ether 33.5 33.5b 35.1 35.1 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Perry, Atkinson, Pitts (1977a). 

c Experimental data not reliable [Atkinson (1989)]. 

d Experimental value from Tuazon et al. (1988). This data is preferred since 

these experiments avoided or have taken into account the side reactions of 

chlorine atoms with the reference compounds [Atkinson (1989)). 

e No experimental value is given in the AOP data base. However, experimental 

values are given in the document Estimation Accuracy of AOP versus PCFAP 

[Meylan (1990b)]. 

f Experimental value from Hatakeyama et al. (1985). 

g Average value from the data of Hatakeyama et al. (1985). 

h Experimental value from Tuazon et al. (1985). 

1 Average value from the experimental data of Harris et al. (1988) and 

Zetzsch (1983) as reported in Atkinson (1989). 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-96- 
experimental data of Harris et al. (1981) and Zetzsch (1983) as 

reported in Atkinson (1989). For 3-chloro-l-propene, the 

recommended value from Atkinson (1989) is 17*, which only has two 

significant figures, compared to a value of 17.0 listed in AOP. 

IV.D.2.b. Evaluation of the Estimated kOH Data 

A comparison of the estimated values of kOH listed in AOP 

and HC for the compounds listed in Table 21 give the same 

results. 

The use of four significant figures in the detailed 

calculations and three significant figures in the summary table 

are applicable in the same manner as described in previous 

sections. 

IV.D.3. Conjugated Dienes 

IV.D.3.a Evaluation of the Experimental kOH Data 

Table 22 compares the pertinent experimental k OHdata at 

298 K for the reaction of OH radicals with conjugated dienes as 

reported in Atkinson (1989), in AOP, and in the literature. A 

comparison of the experimental kOg data in columns 2 and 3 

indicate that they are all different. The difference involves 

the number of significant figures used. For 2-methyl-1,3- 

butadiene, Atkinson (1989) lists a recommended value of 101* and 

not 101.0 as listed in AOP. In all the other cases, AOP 

incorrectly lists kOH to four significant figures whereas the 

literature values listed in Atkinson (1989) and the literature 

contain only three significant figures. 

-97- 
~ 

Table 22. Comparison of the 

Acyclic and Cyclic 

Program (AOP) and 

k0H Data Reported 

in AOP 

Estimated Values of kOH at 298 K for Conjugated ` 

Dialkenes from the Atmospheric Oxidation Computer 

from a Hand Calculation (HC) and the Experimental 

in the Literature Versus the Experimental kOH Data 

10 12 k (cm3 molecule-is-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

A. ACYCLI DIALKENES 

1, 3-Butadiene l06--9c)- o 66.6 66. 6* 66.60009 (h) 

2is-1, 3-Pentadiene 101.0 101b 105 105 

2-Methyl-1, 3-butadienelt'°7-9--T 101.0 101* 105 105 

trans-1,4-Hexadienex 112.0 112 b 106 106 

3-Methyl-1, 3-pentadiene W 4y-3y-() 136.0 136b 135 135 

4-Methyl-1,3-pentadiene g26--%-:~ 131.0 131b 135 135 

2,3-Dimethyl-1,3-butadiene 122.0 122b 135 135 si3- 8/-~ 

2,5-Dimethyl ~ 2,4-hexadie~e

13

_~ 210.0 210b 231 231 

3 -2~ethylene-7~methyl- 1,6- 

octadiene (Myrcene) /23 -3S--3 215.0 215c 194 194 

3,7-Dimethyl-1,3,6-octatriene 252.0 252c 223 223 

1387-7- 9/ - .3 

B. GYCLIC DIALKENES 

1,3-Cyclohexadiene 59a 164.0 164d 137 137 

1, 3-Cycloheptadiene '/O~N ~~ -" 139.0 139e 139 139 

a-Phellandrene q °I-$ 3 - 2- 313.0 313f 187 187 

ac-Terpinene g9 _g6-s- 363.0 363f 235 235 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Ohta (1983). 

c Experimental value from Atkinson, Aschmann, Pitts (1986). 

d Experimental value from Atkinson, Aschmann, Carter (1983). 

e Experimental value from Atkinson, Aschmann, Carter (1984a). 

f Experimental value from Atkinson et al. (1986). 

g Estimated value is the experimental value. 

h Cannot be estimated by the S/R relationship of Atkinson. 

* Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-98- 
IV.D.3.b. Evaluation of the Estimated kOH Data. 

A comparison of the estimated data in columns 4 and 5 of 

Table 22 indicates that they are identical except for the entree 

for 1,3-butadiene. For this compound, the value of 66.6000 

corresponds to the experimental value [which should be 66.6* as 

recommended by Atkinson (1989)] and is not an estimated value. 

There is no entry under the column HC since there is no S/R 

relationship for this compound. 

IV.D.4. Alkynes and 1,2-Dienes (Allenes) 

IV.D.4.a. Evaluation of the Experimental kOg Data 

Table 23 summarizes the pertinent experimental kOH at 298 K 

for the reaction of OH radicals with alkynes and 1,2-dienes 

(allenes) as reported in Atkinson (1989), in AOP, and in the 

literature. A comparison of the experimental kOH data reported 

in columns 2 and 3 are the same except for three differences; 

for propyne and 1-butyne, the correct values with two significant 

figures, as recommended in Atkinson (1989), should be used in 

AOP; the value for 1-hexyne reported by Boodegheans et al. (1987) 

and Atkinson (1989) is 12.6 and not 11.9 as reported by AOP; and 

finally for propadiene, Atkinson (1989) recommended a value of 

9.84* and not 9.82 as reported by AOP. 

IV.D.4.b. Evaluation of the Estimated kOH Data 

Except for ethyne, butadiyne, and propadiene, the estimated 

values of kOH at 298 K in columns 4 and 5 are identical. For 

these three compounds, no estimated values appear under the 

.r 

-99- 
i 

11 

2 2 

Table 23. Comparison of the Estimated Values of k OHat 298 K for Alkynes and 

1,2-Dialkenes (Allenes) from the Atmospheric Oxidation Computer 

Program (AOP) and from a Hand Calculation (HC) and the Experimental 

kOH Data Reported in the Literature Versus the Experimental k OH Data 

in AOP 

10 12 k (cm3 molecule- ls -1 ) 

Chemical Class/Chemic Experimental Estimated 

AOP (a) AOP HC 

A. ALKYNES 

Ethyne (Acetylene) 74/- S"6-4- 0.815 0.815 0.8150b (c) 

Propyne 5.90 5. 9* 6.54 6.54 

1-Butyne /0:7-00-Cfl 8.00 8.0* 7.42 7.42 

2-Butyne 6a 3 - 1-~ - 3 27.4 2 7. 4* 29.3 29.3 

1-Pentyne 6 a7 -/q-0 11.2 11.2d 8.75 8.25 

1-Hexyne 693 - 02 -T 11.9 12. 6d 10.1 10.1 

Butadiyne (Diacetylene) 

NI~O -1"-) -S 

18.9 18.9* 14.08 (c) 

B. 1,2 DIENES (ALLENES) 

Propadiene 'I( 3-419--0 9.82 9.84* 9.820b (c) 

1,2-Butadiene -1"qa- /%-Z 26.1 26.1e 31.1 31.1 

1, 2-Pentadiene ", _ 1,5--,7- 35.5 35. 5e 32.0 32.0 

3-Methyl-1,2-butadiene 56.9 56.9e 57.3 57.3 

sa Experimental values from Atkinson et al. (1989) and the literature. 

b Estimated value is the experimental value. 

c Cannot be estimated by the S/R relationships of Atkinson. 

d Experimental value from Boodaghians et al. (1987). 

e Experimental value from Ohta (1983). 

* Recommended by Atkinson (1989) with the rationale for the recommendation, 

and the uncertainty for the recommendation. 

-100- 
-,, 

4 ~ 

column Estimated/HC since Atkinson never developed S/R 

relationships for these compounds. It should be noted that the 

values listed under the column Estimated/AOP for these three 

compounds are not estimated values but are experimental values 

and there are too many significant figures; they should only have 

3 signif icant f igures . 

IV.E. Reaction of Hydroxyl Radicals with Organic Compounds 

Containing Sulfur, Nitrogen, and Phosphorous Functional 

Groups 

IV.E.1. Reaction with Thiols, Sulfides, and Disulfides 

IV.E.l.a. Evaluation of the Experimental k OH Data 

Table 24 summarizes the pertinent experimental kOH data for 

the reaction of OH radicals with alkyl thiols, sulfides, and 

disulfides as reported in Atkinson (1989), in AOP, and in the 

literature. A careful inspection of the experimental k OH data in 

columns 2 and 3 indicate that they are the same except for a few 

differences. For a few of the compounds, the experimental values 

in Experimental/(a) are listed with only two significant figures 

whereas the data listed in Experimental/AOP have three 

significant figures. A check on the original literature sources 

indicate that the kOH values with two significant figures are the 

correct ones. For example, for 1-butanethiol, the recommended 

value of kOg from Atkinson (1989) is 51* while AOP lists 51.0. 

For methyl ethyl sulfide, the experimental value from Hynes et 

al. (1986) and Atkinson (1989) is 8.50 and not 8.5 as listed in 

AOP. For dimethyl disulfide, AOP does not have an entry in 

column 2 whereas Atkinson (1989) recommends a value of 211*. 

-101- 
~T _ 

a I 

Table 24. Comparison of the Estimated Values of k OHat 298 K for Alkyl 

Thiols, Sulfides, and Disulfides from the Atmospheric Oxidation 

Computer Proqram (AOP) and from a Hand Calculation (HC) and the 

Experimental kOH Data Reported in the Literature Versus the 

Experimental koH Data in AOP 

10 12k (cm3 molecule- ls-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

A. THIOLS 

Methanethiol 32.9 32.9* 32.3 32.3 

Ethanethiol 75-08- 1 46.8 46.8* 38.7 38.7 

1-Propanethiol jv ~- d3~j 48.3 48.3* 42.0 42.0 

2-Propanethiol -7S-3 3- 2 42.0 42.0* 47.8 47.8 

1-Butanethiol/aL?- 79-~ 51.0 51* 43.4 43.4 

2-Methyl-l-propanethiol 45.0 45* 43.5 43.5 

5

3-

/3 - ~y o 

2-Butanethiol ~-j ~6-3_1 40.0 40* 53.7 53.7 

2-Methyl-2-propanethiol 33.1 33.1* 31.6 31.6 

2-Methy1-1-butaZtFiio11 54.0 54.3b 44.9 44.9 

B.1. ACYCLIC SULFIDESe 

Dimethyl sulfide75-18 - 3 4.56 4.56* 4.59 2.59 

Methyl ethyl sulfide 8.5 8.50c 11.0 9.02 

Diethyl sulfide3(ooa- 24'e- 15.0 15* 17.5 15.5 

Di-H-Propyl Sulfidei//-y3 -j 20.0 20.0d 24.0 22.0 

B.2. CYCLIC SULFIDE e 

Tetrahydrothiophene 19.7 19.7* 19.8 17.8 

C. DISULFIDES 

Dimethyl disulfide (f) 211* 203 203 

~ S-I $-3 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Barnes et al. (1986). 

c Experimental value from Hynes et al. (1986). 

d Experimental value from Barnes et al. (1986). The experimental value 

of Nielsen et al. (1987) appear to be erroneous [Atkinson (1989)). 

e For these compounds, kpH was measured in the absence of oxyqen. 

-102- 
_r 

s. a 

Table 24. continued 

f No experimental value is given in the 

value of 211x10 -12 cm3 molecule-ls-1is 

Accuracy of AOP versus PCFAP" [Meyla 

*.Recommended value by Atkinson (1989) 

recommendation, and the uncertainty f 

AOP database. An experimental 

given in the document "Estimation 

n (1990b)]. 

with the rationale for the 

or the recommendation. 

-103- 
yi 

C 

Finally, for 2-methyl-l-butanethiol, the correct experimental 

value of kOH in column 3 is 54.3 obtained from Barnes et al. 

(1986) and Atkinson (1989), and not 54.0 as reported by AOP. 

IV.E.i.b. Evaluation of the Estimated k OH Data 

A comparison of the estimated kOH data from AOP and HC 

indicates that they are the same except for the alkyl sulfides 

(acyclic and cyclic). For all these sulfides, kOHis larger 

from AOP than from HC. The reason for the differences will be 

described in the following paragraphs. 

In estimating kOH, there are two reaction pathways for the 

reaction of OH radicals with alkyl (acyclic and cyclic) sulfides: 

(1) H-atom abstraction from the C-H groups in tl he alkyl groups; 

and (2) OH radical interaction with the sulfide group to form the 

adduct [>S••••OH] which then decomposes rapidly in the presence 

of oxygen to form the products. The total rate of reaction is 

then given by the eq,.sation 

kOH = k(1) + k(4) = k(1) + k(-S-) (57) 

In the absence of oxygen, k(-S-) is zero [Atkinson (1987) and 

Leifer (1992a)] so that equation 57 becomes 

kOH = k(1) (58) 

and only C-H abstraction from the alkyl groups takes place. 

In estimating kOH, AOP uses equation 57 while HC uses 

equation 58 and this is the reason why kOH(AOP) > kOH(HC). 

Since the experimental values listed in the column 

T 

-104- 
Experimental/(a) were obtained in rate measurements without 

oxygen, kOH must be evaluated using equation 58. Therefore, AOP 

must qualify the experimental kpH value for the alkyl sulfides to 

indicate that the data were obtained in the absence of oxygen; 

and thus, only H-atom abstraction occurs. Then, in the detailed 

calculation section, AOP must indicate that k(-S-) = 0 in the 

absence of oxygen. 

IV.E.2. Reaction with Sulfoxides and Sulfates 

IV.E.2.a. Evaluation of the Experimental k OHData 

Table 25 summarizes the pertinent experimental kpgdata at 

298 K for alkyl sulfoxides and sulfates as reported in Atkinson 

(1989), in AOP, and in the literature. A comparison of the 

experimental data in columns 2 and 3 indicate that only for 

dimethyl sulfoxide is there a difference. The experimental value 

from Barnes et al. (1986) and Atkinson ( 1989) is 62 and not 62.0 

as listed in AOP. 

IV.E.2.b. Evaluation of the Estimated kOH Data 

Atkinson did not develop S/R relationships for alkyl 

sulfoxides and sulfates; hence, there are no estimated values 

listed under the column Estimated/HC. Meylan (1990b) did develop 

S/R relationships for these classes of compounds as described in 

the following paragraphs. 

In developing S/R relationships for the alkyl sulfoxides, 

Meylan (1990b) assumed that only C-H abstraction occurred from 

the alkyl group. Therefore, 

-105- 
a 

a.~ 

Table 25. Comparison of Estimated Values of k 0U at 298 K for Alkyl Sulfoxides 

and Sulfates from the Atmospheric Oxidation Computer Program (AOP) 

and from a Hand Calculation (HC) and the Experimental k OH Data 

Reported in the Literature Versus the Experimental k OH Data in AOP 

10 12k (cm3 molecule- ls-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP($Error)f HC 

A. SULFOXIDES 

Dimethyl sulfoxide 62.0 62b 28.5(-54) (e) 

B. SULFATES 

Dimethyl sulfate ~~~~ <0. 5 <0. 5c 1.76 (>+250) (e) 

Diethyl sulfate (~~-~~-`j 1.8 1.8d 11.5(+540) (e) 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Barnes et al. (1986). 

c Experimental value from Japar et al. (1990). 

d Experimental value from Japar et al. (1990a). 

e Atkinson did not develop S/R relationships for alkyl sulfoxides and 

sulfates. 

f Calculated using the experimental value listed in Experimental/(a). 

-106- 
kOH ° k(1) (59) 

F[S(+4) ** ] = 99.000 (Table 2) (60) 

Using equations 59, 60, and 11, AOP estimated that kOH was 28.5 

and the percent error, relative to the experimental value listed 

in the column Experimental/(a), was -54 (listed in parentheses 

adjacent to the estimated value in column 4). However, 

intuitively, it is expected that the sulfoxide group would 

undergo further oxidation to the sulfone in the presence of 

oxygen 

O 

II Rapid 

R-S (=0) + • OH -~ ~S • • • • OH ~ 0 -~ Products ( 61) 

2 

and this reaction pathway should be considered in the S/R 

relationships. Therefore, considerably more experimental kOH 

data are needed on OH radical reaction with a member of alkyl 

sulfoxides (both acyclic and cyclic) and aromatic sulfoxides to 

determine the reaction mechanism and to develop S/R relationships 

for this class of compounds. As a result, it is recommended that 

Meylan drop the S/R relationships for this class of compounds 

from AOP. 

For the alkyl sulfates, Meylan (1990b) assumed that 

kOH = k(1) (62) 

and the substituent factors F(-0-) and F(-CH2-0-) were valid. 

Using equations 62 and il along with the appropriate substituent 

....- ~ 

-107- 
ire . 

(1989) 

(1989) 

(1989) 

(1989) 

10 12 k (cm3molecule- ls-1 ) 

Experimental Estimated 

OP ( a ) AOP HC 

9.0 59.Oc 60.8 60.8 

4.0 244e 80.8 80.8 

2.0 232e 122 122 

5.8 46.8e 124 124 

l.9 31.9e 68.6 68.6 

.~ 

° Experimental data from Atkinson 

c Experimental data from Atkinson 

d Experimental data from Atkinson 

e Experimental data from Atkinson 

and Tuazon et al. (1986). 

and Atkinson et al. (1988) 

and Goodman et al. (1988). 

and Goodman et al. (1988a) 

-112- 
a 

N~ 

trimethyl phosphate, the summary table should be Reaction with 

N,P,S, and OH and the detailed calculation should be 

R,eaction with Nitrocren, Phosphorous, Sulfur, and -OH 

k[P(=0)] = 0.000 (63) 

and for (CH30)2P(=S)NH2, the summary table should be Reaction 

with N,P,S, and OH and the detailed calculation should be 

Reaction with Nitrogen, Phosphorous, Sulfur, and -OH 

k[P(=S)] = 55.0 (64) 

k(NH2) = 20.0 (65) 

IV.F. Reaction of Hydroxyl Radicals with Aromatic Compounds, 

Heterocyclic Aromatic Compounds, and Fused Ring 

Polyaromatic Compounds 

IV.F.1. Aromatic Compounds 

IV.F.i.a. Evaluation of the Experimental kOH Data 

Table 28 summarizes the pertinent kOH data for the reaction 

of hydroxyl radicals with a number of chemicals in a variety of 

classes of aromatic compounds as reported in Atkinson (1989), in 

AOP, and in the literature. A careful inspection of the 

experimental kOH data in columns 2 and 3 indicate that they are 

the same except for some differences. In a few cases, AOP lists 

the experimental values with more significant figures than the 

values reported on the literature. For example, for styrene, AOP 

lists a value of 58.0 while the recommended value by Atkinson 

(1989) is 58*. For aniline, AOP lists a value of 111.0 while 

-113- 
i 

Table 28. Comparison of Estimated Values ofk OH at 298 K for Aromatic =, 

Compounds from the Atmospheric Oxidation Program (AOP) and from a 

Hand Calculation (HC) and the Experimental kQH Data Reported in the 

Literature Versus the Experimental k OH Data in AOP 

10 12k (cm3molecule - ls-1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

A. UNSUBSTITUTED AROMATIC 

COMPOUNDS 

Benzene -7/ - q3 '" 2 1.23 1.23* 2.04 2.04 

Biphenyl Cja Sa 7.2 7.2* 7.12 7.12 

B. ALKYLBENZENES 

Methylbenzene (Toluene) 5.96 5.96* 5.51 5.51 

Ethylbenzene ~y~_y 7.1 7.1* 6.13 6.13 

D-Propylbenzene 6.0 6.0* 7.46 7.46 

,I-Propylbenzene Zfe - 8 2 - 8' 6.5 6.5* 7.08 7.08 

_t-Butylbenzene vb 4.60 4.60b 5.08 5.08 

Q-Xylene 13.7 13.7* 6.88 6.88 

M-Xylene /° g g 23.6 23 . 6* 14.4 14.4 

g-Xylene 14.3 14. 3* 6.88 6.88 

g-Ethyltoluene bl I-Iq-3 12.3 12 . 3* 7.72 7.72 

a-Ethy lto luene &a o-/`~-`/ 19.2 19 . 2* 14.6 14.6 

g-Ethyltoluene ~ ,Pd-910 -9' 12.1 12.1* 7.72 7.72 

1,2,3-Trimethylbenzene 32.7 32.7* 17.8 17.8 

sp(o- 7L 3- $ 1,2,4-Trimethylbenzene 32.5 32.5* 17.8 17.8 

°JS- (03-(a 1,3,5-Trimethylbenzene 57.5 57.5* 37.5 37.5 

/0 51` 60 -~" 3 

-114- 
r 

' Table 28. continued 

10 12 k (cm3 molecule- ls -1 ) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

C. ALKENYLBENZENES 

Phenylethene (Styrene) 58.0 58* 28.2 28.2 

2-Phenyl-l-propene 

(a~ -Methylstyrene)9 g g3 ~ 52c 53.5 53.5 

1-Phenyl-l-propene 

(fl-Methylstyrene) 59c 65.8 65.7 

1-Phenyl-2-methyl1 -propene 

(ft-Dimethylstyrene ~ 33.0 33d 89.1 89.1 

D. HALOBENZENES 

Fluorobenzene y(oa-~ 06-4p 0.69 0.69* 2.56 2.56 

Chlorobenzene 0.77 0.77* 1.43 1.42 

Bromobenzene/v~ - g(9-1 0.77 0.77* 1.28 1.28 

Iodobenzene 5'0))-5- p-4/ 1.1 1.1* 1.34 1.34 

Q-Dichlorobenzene 95' 5a -1 0.42 0.42e 0.414 0.414 

]g-Dichlorobenzene 51f1 - 7-3-1 0.72 0.72e 1.01 1.01 

g-Dichlorobenzene 0.32 0.32e 0.414 0.414 

1,2,4-Trichlorobenzene 0.532 0.532f 0.291 0.291 

1ad -a12 - I 

Hexafluorobenzene 0.172 0.172* 0.151 0.151 

3y2. 3 L-Propylpentafluorobenzene ~ 3.06 3.069 2.89 2.90 

c; ~) ~ } 3r-s 

E. HALOALKYLBENZENES 

Benzotrifluoride jfs'oq`0- 0.46 0.46h 0.406 0.406 

4-Chloro enzotrifluoride 0.24 0.24h 0.285 0.285 

Benzyl c~~ ride c~ 2.9 2. 9* 2.42 2.43 

gg-s$- ~ 

-115- 
-~c _ ~ 

Table 28. continued 

10 12 k (cm3 molecule - ls -1 ) 

Chemical Class/Chemical Experimental Estimated 

✓ AOP (a) AOP HC 

F. MONOCHLOROBIPHENYLS 

2-Chlorobipheny12a51' W --q 2.8 2.82 1 2.95 2.95 

3-Chlorobiphenyl Zd51 - (01-9 5.3 5.28 1 4.42 4.42 

4-Chlorobipheny12a6{-1.2 - 9 3.9 3.86 1 2.95 2.95 

G. HYDROXYBENZENES 

Phenol 26.3 26.3* 35.7 35.6 

2-Cresol 42.0 42* 43.9 43.9 

a-Cresol Iv8-39-4 64.0 64* 93.9 93.9 

p-CresollU(-``H'S 47.0 47* 43.9 43.9 

2,3-Dimethylpheno152to -75-0 80.2 80.27 115 115 

2, 4-Dimethylphenolte,T-ts4-`? 71.5 71. 5j 54.1 54.1 

2,5-Dimethylphenole-75-S, 4A 80.0 80.07 115 115 

2,6-Dimethylphenol546-24r 1 65.9 65.9j 54.1 54.1 

3,4-Dimethylphenol°) ,5°(o ,5 - & 81.4 81.47 115 115 

3, 5 -DimethylphenolfW-G;,g-7 113.0 113i 200.3 200 

2, 3-Dichlorophenol 5'76-2)4-9 1.66 1. 66k 7.27 7.27 

2, 4-DichlorophenolI Za-g_-i- 'L 1.06 1. 06k 3.02 3.02 

H. NITROBENZENES 

Nitrobenzene 0.14 0.149 1 0.251 0.251 

Q-Nitrophenol $V 0.90 0.90 4.42 4.42 

Q-Nitrotoluene S-2- 4Z' 2- 0.70 0.70 0.805 0.805 

M-Nitrotoluene C)4)_,a$- 0.95 0.95 0.605 0.605 

-116- 
.10 

Table 28. continued 

10 12 k (cm3 molecule- is -1 ) 

Chemical Class/Chemica Experimental Estimated 

AOP (a) AOP HC 

I. AMINOBENZENES 

Aniline (o;?-53-:5 111.0 ill* 136 136 

N,N-Dimethylanilinel2l-dr ~- 148.0 148m 263 200 

p-Chloroaniline 83.0 83.0n 53.6 53.6 

2,4-Toluenediamine 192.0 192 0 240 200 

J. ADDITIONAL SUBSTITUTED 

BENZENES 

Methoxyben z ene 100 -(0 6 -3 17.3 17 . 3* 23.8 23.8 

Benzonitrile 100--y4-0 0.33 0.33 0.356 0.356 

Benza ldehyde ) Gb -S a't 12.9 12 . 9* 17.1 17.1 

Acetophenone c38-$G- Z 2.74 2.74p 1.61 1.61 

Thiophenol /0$- 98-6- 

(Mercaptobenzene) 11.2 11.2q 13.3r 13.3r 

Benzyl alcohol /a0-5- 1 -6 22.9 22.9 7.99 7.99 

Tetralin (1,2,3,4- 11y_(a41- Z 

Tetrahydronaphthalene) 34.3 34.3s 11.1 11.2 

Indan (2,3-DihydroiH-indene) 9.2 9.2t 9.71 9.09 

Fluorene (9H-Fluorene) 13.0 13.Ou 9.42 9.37 

810-73-fi 1,4-Benzodioxin 25.2 25.2 33.0 33.0 

2,3-Dihydrobenzo_fura 36.6 36.6 38.0 36.3 

1, 4 -Naphthoqiino~e r~ 3.1 3.1 2.75 2.75 

-117- 
w 

s z 

Table 28. continued 

a Experimental data from Atkinson (1989) and the literature. 

b Experimental data from Ohta and Ohyama (1985). 

c Experimental data from Bignozzi et al. (1981). 

d Experimental data from Chiorboli et al. (1983). 

e Experimental data from Wahner and Zetzsch (1983). 

f Experimental data from Rinke and Zetzsch (1984). 

g Experimental data from Ravishankara et al. (1978a). 

h Experimental data from Atkinson et al. (1985a). 

1Experimental data from Atkinson and Aschmann (1985). 

~ Experimental data from Atkinson and Aschmann (1989). 

k Experimental data from Nolting et al. (1987). 

1 Average of the experimental data of Witle et al. (1986) and 

Zetzsch (1982) as reported in Atkinson (1989). 

m Experimental data from Atkinson et al. (1987).. 

n Experimental data from Wahner and Zetzsch (1983). 

o Experimental data from Becker et al. (1988). 

p Experimental data from Nolting et al. (1987) and Atkinson 

(1989) . 

q Experimental data from Barnes et al. (1986). 

r For the thiol group on an aromatic ring, it was assumed that 

k(4)=k(-SH)=0 [Meylan (1990)]. 

s Experimental data from Atkinson and Aschmann (1988a). 

t Experimental data from Baulch et al. (1986) as reported by 

Atkinson (1989). 

u Experimental data from Kldpffer et al. (1986) and Becker et 

al. (1984) as reported in Atkinson (1989). 

* Recommended value by Atkinson (1989) with the rationale for 

the recommendation and the uncertainty for the 

recommendation. 

-118- 
v~ 

Atkinson (1989) recommends a value of lil*. In a few cases, AOP 

lists fewer significant figures than the values reported in the 

literature. For example, for 4-chlorobiphenyl, AOP reports a 

value of 3.9 while Atkinson and Aschmann (1985) and Atkinson 

report a value of 3.86. 

It should be noted that for 1,4-benzodioxi: n, AOP lists the 

erroneous name 1,4-dibenzodioxin; and finally, for aniline, AOP 

first lists the experimental value for iodobenzene and when a key 

is pressed, the correct experimental value for aniline is 

displayed. 

IV.F.l.b. Evaluation of the Estimated Data 

A comparison of the estimated values of kOHby AOP and HC 

in Table 28 indicates that they are the same except for some 

differences. First, consider the compounds 3,5-dimethylphenol, 

N,N-dimethylaniline, and 2,4-toluenediamine. In all three cases, 

AOP lists a maximum value of the rate constant for OH addition 

to an aromatic ring [i.e., k(7) = kadd,ar, equation 20] as 

200 x 10 -12 cm3molecule- is-1whereas IiC lists a maximum value of 

kOH [equation 9] as 200 x 10 -12 cm3molecule- ls-1 . Since the 

maximum allowed collision rate is 200 x 10 -12 cm3 molecules-1 

[Atkinson (1987)], this boundary condition must be invoked on the 

estimation of kOH and not on the estimation of k(7) = kadd,ar• 

It should be noted that this is only applicable to aromatic 

compounds and not to other compounds (e.g., dimethyl disulfide, 

a-terpinene, a-phellandrene, etc.) 

For the compounds tetralin, indan, and fluorene, AOP makes 

an error in calculating k(7) = kadd,ar• For these three 

-119- 
compounds, AOP uses the incorrect value of v ~ (-CH2-) = 0.06** 

instead of the correct value of -0.064** [see Section IV.A., page 

40, Table 9, No. 41 and Leifer (1992a), Table 22, page 109]. 

Furthermore, for the compounds tetralin, indan, fluorene, and 

2,3-dihydrobenzofuran, which contain five membered rings, AOP 

calculates k(ic) erroneously. That is, for these compounds, AOP 

makes an error by omitting the ring strain factor F(5) for the 

five membered ring. As a result, the values of k OHfor these 

compounds are erroneous. 

Finally, for the compounds 0-methylstyrene, chlorobenzene, 

n-propylpentafluorobenzene, benzylchloride, and phenol, the small 

differences between the estimated kOHfrom AOP and HC are a 

result of the method of rounding off the last digit. 

IV.F.2. Heterocyclic Aromatic Compounds 

IV.F.2.a. Evaluation of the Experimental kOH Data 

Table 29 summarizes the pertinent kOHdata for the reaction 

of hydroxyl radicals with heterocyclic aromatic compounds as 

reported in Atkinson (1989), in AOP, and in the literature. 

Inspection of the experimental kOH data in columns 2 and 3 

indicate that there are a few differences. For pyrrole, the 

recommended value by Atkinson (1989) is 110* whereas AOP reports 

a value of 110.0 which contains one more significant figure than 

is warranted from the experimental data; and for 1,3,5-triazine, 

the value from Atkinson et al. (1987) and Atkinson (1989) is 

0.145 whereas AOP rounds off the data to 0.15. For imidazole and 

-120- 
or 

F+ ~ 

Table 29. Comparison of the Estimated Values of kOH at 298 K for 

Heterocyclic Aromatic Compounds from the Atmospheric 

Oxidation Program (AOP) and from a Hand Calculation (HC) 

and the Experimental kOH Data Reported in the Literature 

Versus the Experimental kOH Data in AOP 

10 12 k (cm3 molecule- ls-1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Furan / 10--00-9 40.5 40. 5* 40. 5b (c) 

3-Methy1furan 9-:ko - 2 - :9 93.5 93.5d 106. 7(+14 ) h (c) 

Thiophene ~ ~ V -r~ 2 ~ 9.53 9.53* 9. 53b (c) 

Pyrrole 

Imidazole 2$$'" 3 2` 

110.0 

36.0 

110* 

35.9e 

1.10.0b 

36.0b 

(c) 

(c) 

Oxazole Zg~- Z/Z-60 9.1 9. le 9. lOb (c) 

Thiazole ! 1.40 1. 41e 1. 40b (c) 

Pyridine 0.37 0.37f 0.370b (c) 

1,3,5-Triazine 0.15 0.1459 0.150b (c) 

a Experimental data from Atkinson (1989) and the literature. 

b Experimental data for this compound. 

c Cannot be calculated by HC since Atkinson did not develop 

S/R relationships for these types of compounds. 

d Experimental data from Atkinson et al. (1989b). 

e Experimental data from Witte and Zetzsch (1986) and Atkinson (1989). 

f Average value from the data of Atkinson et al. (1987) and 

Witle and Zetzsch (1986) as reported by Atkinson (1989). 

g Experimental value from Atkinson et al. (1987) as reported by Atkinson 

(1989). 

h Percent Error from the value of k OH in column Experimental/(a). 

-121- 
, 

f 

thiazole, the correct values of k OH obtained from Witte and 

Zetzsch (1986) and Atkinson (1989) are 35.9 and 1.41, 

respectively, and not 36.0 and 1.40 as listed in AOP. 

IV.F.2.b. Evaluation of the Estimated kOH Data 

Atkinson did not develop S/R relationships for heterocyclic 

aromatic compounds whereas Meylan (1990b) did develop S/R 

relationships for this class of compounds. Meylan used an 

approach similar to the one used by Atkinson for aromatic 

compounds (equations 20, 21, and 22). Thus, Meylan postulated 

that equations 23 and 24 are applicable to heterocyclic aromatic 

compounds where: (1) Ai is a constant which is equal to the 

experimental value of kOH for the parent heterocyclic aromatic 

ring; and (2) the second term is identical to the one used by 

Atkinson for substituents on the aromatic ring [i.e., -1.35 Min 

in equation 21]. The values of Ai are given in Table 

10 for a number of parent heterocyclic aromatic rings. 

The only available experimental kOH data for this class of 

compounds is for 3-methylfuran, a substituted furan. Atkinson 

(1989b) reported a value of 93.5 for this compound. The 

estimated value of kOH obtained from equations 23 and 24 is 

106.7 which gives a percent error of +14 which is excellent. 

However, more experimental kpg data are needed for a number of 

substituted heterocyclic aromatic compounds listed in Table 29 

to confirm the validity of equations 23 and 24. 

-122- 
_ 

t~ 

IV.F.3. Fused Ring Polyaromatic compounds 

IV.F.3.a. Evaluation of the Experimental kOH Data 

Table 30 summarizes the pertinent experimental kOH data for 

the reaction of hydroxyl radicals with fused ring polyaromatic 

compounds (i.e., fused ring polyaromatic hydrocarbons (PAH)). 

Inspection of the data in columns 2 and 3 indicate that they are 

the same except for a few differences. For anthracene, the 

correct value is 112 as reported by Biermann et al. (1985) and 

Atkinson (1989) and not 110.0 as reported by AOP: For 

phenanthrene, the recommended value by Atkinson (1989) is 31* 

and not 31.0 as reported by AOP. 

Unfortunately, there are no available experimental kOg data 

for fused ring polyheteroaromatic compounds published in the 

literature. Hence, there are no entries in Table 30 for this 

class of compounds. 

IV.F.3.b. Evaluation of the Estimated kOH Data 

A comparison of the estimated values of kOH in columns 4 and 

5 of Table 30 indicate that they are the same except for a few 

differences. The differences are related directly to the 

dissimilarity between the S/R relationships of Atkinson 

[equations 26, 27 and 28] and Meylan [equation 29]. First of 

all, AOP uses the experimental value of kOH for the parent PAH 

(which is Bi in equation 29) while Atkinson uses the ionization 

potential of the parent PAH. For naphthalene, both methods give 

essentially the same results; however, for anthracene and 

-123- 
"V 

, 

~ 

Table 30. Comparison of the Estimated Values of k OHat 298 K for 

Fused Ring Polyaromatic Compounds (PAH) from the 

Atmospheric Oxidation Program (AOP) and from a Hand 

Calculation (HC) and the Experimental kOH Data Reported 

in the.Literature Versus the Experimental k OHData in AOP 

10 12k (cm3 molecule - ls -1 ) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

Naphthalene 91-.2 O- 3 21.6 21. 6* 21. 6b 21.4 

1-Methylnaphthalene 90-/2-v 53.0 53 . Oc 56.9 56.3 

2-Methylnaphthalene9i-S7-U 52.3 52.3d 56.9 56.3 

2,3-Dimethylnaphthalene 76.8 76.8d 70.0 69.5 

~~ /- yv-8 1-Nitronapht2Salene 

&0-SF' * 2-Nitronaphthalene 

58I~ &y-S 

1,4-Dichloronapht alene 

5.4 

5.6 

5.8 

5.4e 

5.6e 

5.8f 

2.66 

2.66 

4.38 

2.63 

2.63 

4.37 

Anthracen e ',Q ~~ z, ~ 

Phenanthrene 

110.0 

31.0 

1129 

31* 

110. Ob 

31.0b 

91.2 

22.9 

as`'G7/" EN 

a Experimental data from Atkinson (1989) and the literature. 

b Experimental data for this compound. 

c Experimental data from Atkinson and Aschmann (1987). 

d Experimental data from Atkinson and Aschmann (1986). 

e Experimental data from Atkinson et al. (1989d). 

f Experimental data from Klt3pffer et al. (1986) and Becker et al. (1984) 

as reported in Atkinson (1989). 

g Experimental data from Biermann et al. (1985). 

* Recommended values by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-124- 
p 

." 

phenanthrene, AOP gives the most reliable results. For the 

substituted naphthalenes, AOP and Atkinson (HC) give essentially 

the same results. However, more experimental kOH data are needed 

for considerably more substituted polyaromatic hydrocarbons to 

see how reliable both methods are. 

Since there are no experimental kOH data for fused ring 

heterocyclic polyaromatic compounds (i.e., quinoline, 

isoquinoline, quinoxaline, quinazoline, and acridine), Meylan's 

S/R method cannot be evaluated. Thus, experimental kOH data is 

needed on a number of compounds in this class of compounds to 

confirm and refine the AOP method (i.e., equation 30). 

IV.G. Evaluation of the Estimated Half-Life for the Reaction 

of Hydroxyl Radicals with Organic Chemicals in the 

Troposphere 

Meylan (1990b), in AOP, estimated the half-life [t(1/2)E] 

for the reaction of hydroxyl radicals with organic chemicals in 

the troposphere by assuming that the average OH radical 

concentration was 5 x 10 5radicals cm-3and a 24-hour daylight 

day. The assumption of a 24-hour daylight day is incorrect. On 

the average, a 12-hour daylight day is more reasonable. [Leifer 

(1992a)]. In addition, based on the literature data (Leifer 

(1992a)], the average OH radical concentration is closer to 1.5 x 

10 6radicals cm 3 . Therefore, it was recommended that the AOP 

computer program be changed to the atmospheric conditions 

described above. This has been done by Meylan in a later version 

of AOP. 

-125- 
i 

~ 

9 

For olefins and acetylenes, which can react with hydroxyl 

radicals and ozone, it is desirable to have knowledge of the 

overall oxidative half-life in the troposphere. Therefore, 

kOX = k OH + k03 (66) 

where k 'OH and k ~3are the first-order rate constants for 

reaction of an organic chemical in the troposphere with respect 

to hydroxyl radicals and ozone, respectively, as calculated under 

the atmospheric conditions (OH) = 1.5 x 10 6radicals cm-3and a 

12-hour daylight day and (03) = 7 x 1011molecules cm-3 ; and the 

overall oxidative half-life is given by the equation 

I t(1/2),OX = 0.693/kOX (67) 

Thus, AOP should add 

SUNIIKARY : OXIDATION 

kOX = (68) 

t ( 1 / 2 )OX = (69) 

-126- 
.~ 

s 

J. a 

V . Ref erences 

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Environ. Sci. Technol. 2a, 321-327. Diurnal Concentrations of 

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Z. Physik Chem. _X, 110. 

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Atkinson, R. (1988). 

Env. Toxic. and Chem. 7, 435-442. 

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-127- 
i 

'.~ 

Atkinson, R. (1987b, 1988a). 

In OECD (Organization for Economic Cooperation and Development) 

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1. Draft Final Report Dated January, 1987b. Revision 2, p. 49- 

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2. Draft Final Report Dated August, 1988a. Revision 3, p. 19-42 

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K . 

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Atmos. Environ. al , 2323-2326. 

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• F 

! S 

-128- 
.~ 

: 

~ 

Atkinson, R.; Aschmann, S.M. (1988a). 

Int. J. Chem. Kinet. 2Q, 513-539. 

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a Series of Aromatic Hydrocarbons at 296 ± 2 K. 

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Rate Constants for the Reaction of the OH Radical with the Propyl 

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Chem. Rev. $4, 437-470 

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CH3 NH2over the Temperature Range 299-426 K. 

-129- 
Atkinson, R.; Perry, R.A.; Pitts, Jr., J.N. (1978). 

J. Chem. Phys., 1850-1853. 

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Arch. Environ. Contam. Toxicol. 19, 417-425. 

Atmospheric Gas Phase Loss Processes for Chlorobenzene, 

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r 

~ 

~ 

! y 

-130- 
~r 

~ 

~• 

Atkinson, R.; Aschmann, S.A.; Goodman, M.A.; Winer, A.M. (1988). 

Int. J. Chem. Kinet. 2,0_, 273-281. 

Kinetics of the Gas-Phase Reactions with the OH Radical with 

(C2HSO)3P(0) and (CH30)2P(S)C1 at 296 ± 2 K. 

Atkinson, R.; Baulch, D.L.; Cox, R.A.; Hampson Jr., R.F.; Kerr, 

J.A.; Troe, J. (1989a). 

Int. J. Chem. Kinet. ZI, 115-150. 

Evaluated Kinetic and Photochemical Data for Atmospheric 

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Atkinson, R.; Aschmann, S.M.; Tuazon, E.C.; Arey, J.; Zillinska, 

B. (1989b). 

Int. J. Chem. Kinet. 21, 593-604. 

Formation of 3-Methylfuran from the Gas-Phase Reaction of OH 

Radicals with Isoprene and the Rate Constant for its Reaction 

with OH Radicals. 

Atkinson, R.; Baulch, D.L.; Cox, R.A.; Hampson Jr., R.F., Kerr, 

J.A.; Troe, J. (1989c). 

J. Phys. Chem. Ref. Data 18, No. 2, 881-1097. 

Evaluated Kinetic and Photochemical Data for Atmospheric 

Chemistry, Supplement III. 

Atkinson, R.; Aschmann, S.M.; Arey, J.; Zielinska, B.; 

Schuetzles, D. (1989d). 

Atmos. Environ. 21, 2679-2690. 

Gas-Phase Atmospheric Chemistry of 1- and 2-Nitronaphthalene and 

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Barnes, I.; Bastian, V.; Becker, K.H.; Fink, E.H.; Nelson, W. 

(1986). 

J. Atmos. Chem. 4, 445-446. 

Oxidation of Sulfur Compounds in the Atmosphere: I. Rate 

Constants of OH Radical Reactions with Sulfur Dioxide, Hydrogen 

Sulfide, Aliphatic Thiols and Thiophenol. 

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~ 

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pEPOR7 DOCUMEN7ATION 1. REPORT NO. 2. 3. Recipient's Accession No. 

PAGE EPA-744R-93-001 

S. Report Date 

4, TIfM end Subtitle DETERMINATION OF RATES OF REACTION IN THE GAS-PHASE IN THE Jenuary 1993 

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