EPA-744-R-93-001 

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 

by 

Asa Leifer 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

OFFICE OF POLLUTION PREVENTION AND TOXICS 

WASHINGTON, DC 20460 
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. 

III.B. 

IV. 

IV.A. 

IV.B. 

IV.C. 

IV .C.l. 

IV .C.l.a. 

IV .C.l.b. 

IV.C.2. 

IV.C.2.a. 

IV.C.2.b. 

IV.C.3. 

IV.C.3.a. 

IV.C.3.b. 

Introduction • • . . . . . . . . . . . . . . . . 

Atmospheric Oxidation Computer Program (AOP) 

Evaluation of the Atmospheric oxidation 

computer Program for Estimating koa and 

the Experimentally Measured koa Data 

Listed in the Program . • . . • • . . • 

comments on the Group Rate Constants, 

Substituent Factors, and Other Parameters 

Used by the Atmospheric Oxidation Program 

. . . . 

. . . 

14 

15 

29 

29 

some Comments on Hydroxyl Radical Addition to 

Heteroaromatic and Fused Polyaromatic Ring 

systems • • • • . • • • • • . • • • . . • . . . 46 

H-Atom Abstraction from c-H and -OH Groups by 

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

Saturated Alkanes . . . . . . . . . . . . . 52 

Evaluation of the Experimental koa Data 52 

Evaluation of the Estimated koa Data . . . . 57 

Haloalkanes . . . . . . . . . . . . . . . . . . 59 

Evaluation of the Experimental koa Data . . . . 59 

Evaluation of the Estimated koa Data . . . . 62 

carbonyl Compounds . . . . . . . . . . . . . 62 

Evaluation of the Experimental koa Data 62 

Evaluation of the Estimated koa 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 

rv.c.s.a. Evaluation of the Experimental koH Data . . . . 79 

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

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

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

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

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

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

IV.C.7.b. Evaluation of the Estimated koa 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.1.a. Evaluation of the Experimental koa Data . . . . 89 

IV.D.1.b. Evaluation of the Estimated koH Data . . . . 93 

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

IV.D.2.a. Evaluation of the Experimental koa Data . . . . 94 

IV.D.2.b. Evaluation of the Estimated koa Data . . . . 97 

IV.D.J. Conjugated Dienes . . . . . . . . . . . . . . . 97 

IV.D.J.a Evaluation of the Experimental koa Data . . . . 97 

IV.D.J.b. Evaluation of the Estimated koH Data. . . . . . 99 

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

IV.D.4.a. Evaluation of the Experimental koH Data 99 

IV.D.4.b. Evaluation of the Estimated koa Data . . . 99 

iii 
IV.E. 

IV. E.l. 

IV. E.l. a. 

IV. E.l. b. 

IV.E.2. 

IV.E.2.a. 

IV.E.2.b. 

Reaction of Hydroxyl Radicals with Organic 

Compounds Containing Sulfur, Nitrogen, and 

Phosphorous Functional Groups • • . • . • 

Reaction with Thiols, Sulfides, and Disulfides 

Evaluation of the Experimental koH Data . . . 

Evaluation of the Estimated koH Data . . . . . 

Reaction with Sulfoxides and Sulfates . . . . 

Evaluation of the Experimental koH Data . . . 

Evaluation of the Estimated koH Data . . . . 

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

. 101 

. 101 

. 101 

. 104 

. 105 

. 105 

. 105 

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

IV.E.J.a. Evaluation of the Experimental koH Data 108 

IV.E.J.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. 

IV.F.l. 

IV. F~ La. 

Reaction of Hydroxyl Radicals with Aromatic 

Compounds, Heterocyclic Aromatic Compounds, 

and Fused Ring Polyaromatic Compounds . . • 

Aromatic Compounds • • • • • • . . . . . . 

Evaluation of the Experimental koH Data 

IV.F.l.b. Evaluation of the Estimated Data •.•. 

IV.F.2. 

IV.F.2.a. 

IV.F.2.b. 

IV.F.3. 

IV.F.J.a. 

Heterocyclic Aromatic compounds 

Evaluation of the Experimental koH Data 

Evaluation of the Estimated koH Data . . 

. . . 

Fused Ring Polyaromatic Compounds . . . . 

Evaluation of the Experimental koH Data 

IV.F.J.b. Evaluation of the Estimated koH Data .•. 

iv 

113 

. 113 

. 113 

119 

. 120 

. 120 

. 122 

. 123 

. 123 

. 123 
IV.G. 

v. 

Evaluation of the Estimated Half-Life for 

the Reaction of Hydroxyl Radicals with 

Organic Chemicals in the Troposphere 

References • • . . . . • . . . . . . . . 

v 

• 125 

• • • • 12 7 
Table 1. 

Table 2. 

Table 3. 

Table 4. 

Table 5. 

Table 6. 

Table 7. 

Table 8. 

Table 9. 

Table 10. 

Table 11. 

Table 12. 

LIST OF TABLES 

Group Rate Constants for Hydrogen Abstraction 

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

Substituent F(X} Factors for Hydrogen 

Abstraction • • • . . • . • . • . . . . . 31 

Factors Used for Aliphatic Ring Strain 

Effects . • . . . • • • . . . . . 33 

Group Rate Constants for OH Radical Addition 

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

Group Rate Constants for OH Radical Addition 

to Conjugated Olefinic Units • • • • • • • • • 35 

Group Rate Constants for OH Radical Addition 

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

Group Rate Constants for OH Radical Addition 

to 1,2-Dialkene (Allene} Units • • • . . • 38 

Substituent Factors [C(X}] for OH Radical 

Addition to Olefins and Acetylenes • • • 

Electrophilic Substituent Factors for OH 

Radical Addition to Aromatic Rings • 

. . . 

. . . 

Experimental Values of Ai for Some 

Monocyclic Heteroaromatic Compounds . . . . . 

Experimental Values of Bi for some 

Polynuclear Aromatic Compounds . 

Values of Bi for Polynuclear Aromatic 

Hydrocarbon Structures Derived from 

Experimentally Measured Ionization 

Potentials . • • • • • • • • . • . • • 

. . . . 

. . . . 

39 

40 

47 

48 

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 

koH at 298 K for saturated Acyclic Alkanes from the Atmospheric oxidation 

Computer Program (AOP} and from a Hand 

Calculation (HC} and the Experimental 

koa Data Reported in the Literature 

versus the Experimental koH Data 

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

vi 
Table 14.B. 

Table 15. 

Table 16. 

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 • • • • • • • . • • . . . . . . 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 • • • • • • • • • • • 

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 

. . . 

55 

60 

Versus the Experimental koH Data in 

AOP • • • • • • • • • • • • • • . . • . . • . • 6 3 

Table 17. 

Table 18. 

Table 19. 

Comparison of the Estimated Values of 

koH at 298 K for Alcohols, Glycols, Ethers, and Hydroperoxides 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 . • • • • 

Comparison of the Estimated Values of 

koH 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 . • • • • . • • • • • . . . . . 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 . . • . . • . . • • . 

vii 

. . . . . 

72 

80 

83 
Table 20. 

Table 21. 

Table 22. 

Table 23. 

Table 24. 

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 

Comparison of the Estimated Values of 

koH 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 • • • • • • • • • • • • • • • • . • • • . . 9 5 

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 • • • • • • • • • • • • • • 

Comparison of the Estimated Values of 

kQH at 298 K for Alkynes and 1,2-

D1alkenes (Allenes) from the 

Atmospheric Oxidation Computer Program 

(AOP) and from a Hand Calculation (HC) 

. . . . 98 

and the Experimental koH Data Reported 

in the Literature Versus the 

Experimental koH Data in AOP. . • . • • • • . • 100 

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 
Table 25. 

Table 26. 

Table 27. 

Table 28. 

Table 29. 

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 

koH Data Reported in the Literature 

Versus the Experimental koH Data in 

AOP • • • • . • • • • • • • • • • • . . • • . . 106 

Comparison of the Estimated Values of 

koH 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 

koH Data Reported in the Literature 

Versus the Experimental koH Data in 

AOP • • • • • • • . • • • • • • • . • . • . . . 109 

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 

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 

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 •••••••....•.......... 121 

ix 
! 

·. 

Table 30. Comparison of the Estimated Values of 

koa at 298 K for Fused Ring Polyaromatic Compounds (PAH) from the 

Atmospheric Oxidation Program (AOP) and 

from a Hand Calculation (HC) and the 

Experimental koa Data Reported in the 

Literature Versus the Experimental koa 

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

X 
Figure 1. 

Figure 2. 

Figure 3. 

Figure 4. 

Figure 5. 

LIST OF FIGURES 

Atmospheric Oxidation Program Data 

Entry Display • • • • • . • • • • . . . . . Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene {2-Phenyl- 1-Propene): 

summary Hydroxyl Radical Data and Experimental Data. 

A. Screen Display when Key PgDn is pressed. 

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

Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene {2-Phenyl- 1-Propene) : 

Summary Hydroxyl Radical and Ozone Data. 

A. Screen Display when Key PgDn is pressed. 

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

Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene {2-Phenyl- 1-Propene) : 

A. Screen Display of the Detailed Calculations 

for Hydrogen Abstraction. 

B. Screen Display of the Detailed Calculations 

for OH Radical Addition to the Olefinic 

Bond. . . . . . . . . . . . . . . . . . 

. . . . . . . 

Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene {2-Phenyl- 1-Propene) : 

A. Screen Display of the Detailed 

Calculations with o3 Reaction with the 

Olefinic Bond. • • • • • • • • • • . . . . 

16 

18 

19 

22 

23 

24 

25 

26 B. Screen Display of the Detailed 

Calculations of OH Radical Addition to the 

Aromatic Ring. • • • • • • . • • • . • • 2 7 

Figure 6. Atmospheric Oxidation Program Data Display 

for the Compound a-Methyl Styrene {2-Phenyl- 1-Propene) : 

Screen Display for OH Addition to the 

Aromatic Ring and the Experimental Data. . . 28 

xi 

.· 
·. 

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 (koa>· 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 koa for a large number of organic 

chemicals in AOP2 • 

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 k08 , lists an 

experimental value (if available from the scientific literature), 

1 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 (ko ) in the gasphase in the troposphere. This report, howe~er, 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 kNOJ for the reaction 

of an organic chemical with nitrate radicals (N03), 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 koH from AOP with the hand 

calculated and experimental values of Leifer for 454 organic 

compounds covering a wide variety of classes of compounds. These 

koa data 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 k0H, respectively) with up to a 

maximum of six significant figures. However, the group rate 

constants (e.g., k~, k~, k~, k~s, k~ , k(>N-), k(-SH), etc.) and 

the substituent factors F(i) and C(i) [e.g., F(-CH2-), F(-Cl), 

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

C(-C•N), 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(lc), 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-) = o so that only H-atom 

abstraction is observed. However, AOP estimates koH by assuming 

that k(-S-) = 2.0 and not o. Hence, when estimating koH for 

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 
cm3molecule-ls-l (i.e., k(7) = kadd,arl wher~~ HC lists a 

Since the 

maximum allowed collision rate is 200 x lo-12cm3molecule-ls-1 

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

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

using this boundary condition, the estimated values of koa for 

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,arl· For these compounds, AOP uses the 

incorrect value of a:(-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(lc) for these compounds, AOP makes an error by 

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

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 koa data. 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 

t 
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(=O)OH, 

[k(2)]} and from the c-H groups in the alkyl group [k(1a)] 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(1a). Therefore, it is recommended 

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

hydroperoxides be deleted from AOP. More experimental koH data 

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 

koH data with the experimental k08 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 k08 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 k08 data 

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 k08 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 

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 ~-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 trans-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 koa 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; ~3-carene; sec-butyl acetate; and 2-

(chloromethyl)-3-chloro-1-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 

xvi~i 
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 (N03) 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 kdEr 

k0a, and ko • The rate constant kdE represents the first-order 

3 

rate constant for direct photoreaction, while koa and ko 

3 

represent second-order rate constants for indirect photoreaction 

and oxidation with OH and o3, respectively. 

-1-
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' k0H, and k03 and the half-lives (tc 1/ 2)El 

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 [kdElmax and the minimum half-life 

[t(1/2)Elmin 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 koH 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 

Taxies, 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 koH as reported 

-2-
in the literature [Meylan (1990b)]. This document, describes an 

assessment of this computer program for estimating k08 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 

analyzed the hydroxyl radical rate data (koa> 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: 

H-atom abstraction from acyclic ] 

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

unsaturated c-H groups by OH radicals 

k(2) 

= k ra-atom abstraction from 0-H groups] 

Lby OH radicals 

r

OH radical addition to >C=C<, ] 

k(J) = k >C=C-C=C<, -C•C-, and >C=C=C<, >C=C=O groups 

k(4) k [OH radical interaction with -SH,] 

= -s-, and -s-s- groups 

k(S) = k [OH radical interaction 

>NH, and >N- groups 

with -NH2 '] 

-3-

( 1) 

(2) 

( 3) 

( 4) 

(5) 
k (6) 

k(7) 

= k roH radical interaction with] lPhosphorus groups 

= k [OH radical addition to aromatic rings] 

H radical addition to fused ringJ k(8) = k polyaromatic compounds (i.e., 

olyaromatic hydrocarbons) 

(6) 

(7) 

(8) 

Atkinson postulated that the overall OH radical rate constant k

08 

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 

koH = L k(i) 

I • 1 (9) 

and the individual rate constants [k(1), k(2), · · · · ·, k(8)J and 

koH are all in the units cm3molecule-1s-1. Structure; 

reactivity relationships will be described for each of these 

reaction pathways. 

Pathway 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(1a) + k(1c) + k(1, UNS CH) (10) 

where k(1a) represents the rate constant for H-atom abstraction 

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

-4-
k(1c) 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(1a) is given by the mathematical 

relationship 

k(1a} = ~ ms 

k(1c) = l~ ;tr, 

k(1, UNS CH} = 0 

(11) 

(12) 

(13) 

where k~, kg, k~ 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; ~ ~ L ~ L represent the ms I .tr.S 1 

111(8) 

1 rtt, I III(C) 

1 

summation over all primary acyclic, secondary acyclic, tertiary 

acyclic, secondary and tertiary cyclic groups, respectively, in 

3 Group Rate Constants and Substituent Values Used by the 

Atmospheric Oxidation Program, Version 1.30, November 1, 

1990. 

-s-
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. 

Patbway 2: H-Atom abstraction from -0-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(-0-H) k(-OH) (14) 

where n(-0-H) represents the number of hydroxyl groups (-0-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 1o-12cm3molecule-1s-1 at 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). 

-6-

: 

• 
Pathway 3: OH radical addition to isolated alkene groups (>C=C<), nonaromatic conjugated groups 

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

(-C•C-, >C=C=C<, >C=C=O) 

The overall rate constant for reaction pathway 3 is given 

by the equation 

k(3) = kadd,nar 

= ~kAsci(X)Ci(Y) + ~kg cj(X)Cj{Y) + 

+ l: kgucm(X)Cm(Y) 

• 

(15) 

where kAs, kgo, kgu 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; l:' l:, 1 J 

l:, 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 a, 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. 

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

The overall rate constant for reaction pathway 5 is given 

by the equation 

k(S} = 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 

-a-
• 

.... 

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 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(O)-]k[>P(O)-] 

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

(18) 

where n[>P(S)-], n[>~(O)], n[>P(Cl)<] represent the number of 

>P(S)-, >P(O)-, and >P(Cl)< groups, respectively, in the 

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

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

>P(O)-, and >P(Cl)< 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,arl 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'). 

-9-
For reaction of OH radicals with an aromatic ring 

k(?A) = kadd,ar {20) 

log1ok~add,ar = ~ [ 0.31- 1.35 Min { ~aj ~ {21) 

kadd,ar = 10-12 kadd,ar {22) 

where ~ represents the summation over all aromatic rings in the 

molecule; <l:aj) represents the summation of the electrophilic 

J 

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

a given ring position (i.e., ortho, meta, para); and Min{l:aj) 

J 

aj ) 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 (a~ and a~) 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 (ar'), AOP uses the equation 

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

1.10, November 1, 1990. 

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

log1okadd ar' = l: [ Ai - 1.35 Min ( l:aj )] , 1 J 

(24) 

where l: represents the summation over all heteroaromatic rings, 

1 

Ai is a function of the experimental value of kadd,ar' of the 

basic, or parent, heteroaromatic ring in the units 10-12 

cm3molecule-1s-1 [Table 10, Section IV, of this report and on 

page 7 of a document by 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) 

= l:[10.11- 1.08 (IP)i- 1.35 Min( l:aj)] (27) 

1 

-11-
(28) 

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

the ionization potential of the parent PAH in electron volts 

(eV) obtained from Weast {1976-1977); { l:aj) is derived for the 

J monocyclic substituted portion of the molecule to allow for the 

effects of substituent qroups on the reactivity and represents 

the summation of the electrophilic substituent constants of Brown 

and Okamoto (1958) with respect to a qiven rinq position (i.e., 

ortho, meta, para); and Min ( l:aj) represents the summation of 

J the electrophilic substituent constants with respect to the ring 

hydroqen position that qives the most neqative summation (i.e., 

Min). Electrophilic substituent constants {a~ and a~) for a 

number of substituents are qiven 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 rinqs, Meylan (1990b) 3 , developed a different 

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

loq10kadd PAH = l: [ Bi - 1.35 de+ ] I I ) 

(29) 

where l: represents the summation over all fused polynuclear I 

aromatic hydrocarbon rinqs, Bi is a function of the experimental 

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

hydrocarbon aromatic rinq in the units 1o-12cm3molecule-ls-l 

-12-
[Table 11, 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 1o-12cm3molecule-1s-1 [Table 12, 

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

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

substituent factors a~ and a~ for various substituents and is 

determined in the following way. For monosubstituted PAH 

compounds, dej corresponds to the most negative value of a+ m or a+ p 

for a given substituent on the ring. For polysubstituted PAH 

compounds, dej corresponds to the sum of the average values of a~ 

and a~ for each substituent on both rings. 

For OH radical addition to polynuclear heteroaromatic rings 

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

is 

= l: [ Bi 

1 

- 1. 35 de"! 

J (30) 

where Bi ' is now related to the experimental ionization potential 

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

the units 1o-12cm3molecule-1s-1 [obtained from Table 13, Section 

IV, of this report for a few fused polynuclear heteroaromatic 

rings and from Meylan (1990b) 4]. The term dej 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 Taxies, 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 CkoH> and ozone (k03 ) in the gas-phase. These rate 

constants are then used to calculate the half-life [tc 1; 2)El 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 5/R relationships of Atkinson and Carter 

(1984) for ozone and the evaluation of AOP for estimating k03 and 

the corresponding half-life [t(1/2)EJ· 

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 k08 and tc 1/ 2)E will be discussed in this report. 

AOP has been designed for use in an IBM or an IBM-compatible 

series of personal computers running the MS-DOS or PC-DOS 

operating systems. Approximately 350 K of free memory are 

required to run AOP. All program outputs occur in the text mode 

and are run from a floppy disk drive. 

The AOP program is started by pressing key 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-
Figure 1. Atmospheric Oxidation Program Data Entry Display 

Version: IHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH; 

SRC 1.30 : ATMOSPHERIC OXIDATION PROGRAM : 

Nov 1990 : Rate of Hydroxyl Radical & Ozone : 

: Reaction from Chemical Structure : 

HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH( 

... 

IHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH; 

:oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo: 

: Enter SMILES:O 000: 

:000000000000000 000: 

:oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo: 

: Enter NAME :0 000: 

:000000000000000000000000000000000000000000000000000000000000000000000000000000: 

HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH< 

INS: OFF 

ZDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD? 

3 Fl: CLEAR Input F6: Save Input to User File PgDn: CALCULATE 3 

3 F2: PREVIOUS Input F8: CAS File Input Alt-H: SMILES HELP 3 

3 F4: User FILE Input FlO: CALC & SAVE Results Esc: EXIT to DOS 3 

~DDDDDDDDDDDDDDDDDDDDDODDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDY 

-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 koa and tc 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-1-propene) which has a SMILES notation C=C(C)c1ccccc1. 

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

-17-
Figure 2. Atmospheric Oxidation Program Data Display for the 

Compound a-Methyl Styrene (2-Phenyl-1-Propene): 

Summary Hydroxyl Radical Data and Experimental Data. 

Figure 2A 

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 = 

Reaction with N, S and -OH = 

Addition to Triple Bonds = 

** Addition to Olefinic Bonds = 

** Addition to Aromatic Rings = 

Addition to Fused Rings = 

.1440 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

51.4000 E-12 cm3/molecule-sec 

1.9187 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

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

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

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

ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

-----3 3--

0V3 Name: 2-Phenyl-1-propene <<-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 N03 rate constant cm3/molecule-sec 3 

3 3 

3 3 

@DDDDDDDDDDDDDDDDDD4 Press any key to continue ... CDDDDDDDDDDDDDDDDDDDY 

-18-
Fiaure 2B 

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

SMILES : C=C<C)c1ccccc1 

CHEM 

MOL FOR: C9 1-110 

MOL WT : 118. 18 

INNHNMHHMHHHMMMHHMMMMM: 

: Summary Saved to: . 

: file --) AOP1.DAT . 

HHHHMMMHMMHMMHNHHNNNMM~ 

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

Hydrogen Abstraction = 

Reaction with N, S and -OH = 

Addition to Triple Bonds = 

** Addition to Olefinic Bon·ds = 

** Addition to Aromatic Rings = 

Addition to Fused Rings = 

. 1440 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

51.4000 E-12 cm3/molecule-sec 

1.9187 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

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

HALF-LIFE = .300 Days Cat cone 5E5 yOH/cm3> 

........•.••...•.•....•• **Designates Estimation(s) Using ASSUMED 'v'.:.due(s) 

ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

-----3 3--

0V.3 Name: 2-Pheny 1-1-p t'opene <cC.-methy 1 styt'ene) 3 

HAJ CAS Number: 00098-83-9 3 

3 Exper OH rate constant 

J Exper Ozone rate constant 

3 Exper N03 rat~ constant 

3 

3 

52.(> E-12 cm3/molecule-sec 

cm3/molecule-sec 

cm3/molecule-sec 

@DDDDDDDDDDDDDDDDDD4 Press any key to continue ... 

3 

CDDDDDDDDDDDDDDDDDDDY 

-19-
SMILES notation, molecular formula, and molecular "rqight 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-3 and a 24-hour daylight day. 

The table in the lower box summarizes the available 

experimental k0H, k03 , and kNOJ data for this compound. The 

experimental value of koH is listed as 52.0 E-12 cm3molecule-1s-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 (kNo3). 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 

SUMMARY: OZONE REACTION data replaces the available experimental 

-20-
data, Figure JA. The ozone data corresponds to the overall 

estimated ozone rate constant (k03 ) and the associated half-life 

[t( 1

/

2

)El in days corresponding to an average ozone concentration 

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

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

twice, then the results are depicted in Figure J.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(1a)], 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 S.A.; 

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

kadd,ar], Figure S.B; and 

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

for OH addition to the aromatic ring (Figure S.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 Display for the 

Compound a-Methyl Styrene (2-Phenyl-1-Propene): 

Summary Hydroxyl Radical and Ozone Data. 

Fiaure JA 

A. Screen Display when Key PgDn is pressed. 

SMILES : C=C<C)clcccccl 

CHEM 

MOL FOR: C9 H10 

MOL WT : 118. 18 

; 

------------------------- SUMMARY: HYDROXYL RADICALS ------------------------- Hydrogen Abstraction = 

Reaction with N, S and -OH = 

Addition to Triple Bonds = 

** Addition to Olefinic Bonds = 

** Addition to Aromatic Rings = Addition to Fused Rings = 

.1440 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

51.4000 E-12 cm3/molecule-sec 

1.9187 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

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

HALF-LIFE = .300 Days Cat cone 5E5 y0H/cm3) 

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

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

HALF-LIFE = .084 Days <at cone 7E11 mol/cm3) 

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

-22-
... 

... 

Figure 3B 

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

SMILES : C=C<Clc1ccccc1 

CHEM 

MOL FOR: C9 H10 

1"'10L WT : 118. 18 

IHHNNHNMMHMMMHMMMMNNHM: 

: Summary Saved to= 

: file --> AOP1.DAT 

HMMMNMMMNMNMMNNHNMNHMM· 

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

Hydrogen Abstraction = 

Reaction with N, S and -OH = 

Addition to Triple Bonds = 

** Addition to Olefinic Bonds = 

** Addition to Aromatic Rings = 

Addition to Fused Rings = 

.1440 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule~sec 

.0000 E-12 cm3/molecule-sec 

51.4000 E-12 cm3/molecule-sec 

1.9187 E-12 cm3/molecule-sec 

.0000 E-12 cm3/molecule-sec 

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

HALF-LIFE = .300 Days (at cone 5E5 yOH/cm3l . . . . . • . . . . . • . . . . . . . . . . . . **Designates Estimation(s) Using ASSUMED ',,'alue(s) 

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

HALF-LIFE = .084 Days <at cone 7E11 mol/cm3) 

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

-23-
Figure 4. Atmospheric Oxidation Program Data Display for the 

Compound a-Methyl Styrene (2-Phenyl-1-Propene): 

Figure 4A 

A. Screen Display of the Detailed Calculations for 

Hydrogen Abstraction. 

Hydrogen Abstraction 

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

Kprim = 0.144 FC>C=C<J = 0.144 < 1.000) = . 144 

H Abstraction TOTAL = .144 E-12 cm3/molecule-sec 

Press any key to continue 

-24-

... 
... 

... 

Figure 4B 

B. Screen Display of the Detailed Calculations for 

OH Radical Addition to the Olefinic Bond. 

OH Addition to Olefinic Bonds 

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

Kd - K<CH2=C<lC<-Phenyl **l 

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-1-Propene): 

Figure SA 

A. Screen Display of the Detailed Calculations with 

o3 Reaction with the Olefinic Bond. 

Ozone Reaction with Olefins 

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

ko- K(CH2=C-R2lOx<-CH3l0xC-Aromaticl 

• 1 75ooo c 6. ::_;oo > < 12. ooo' - 13.650000 E-17 cm3/molecule-sec 

Press any key to continue 

-26-
Figure SB 

B. Screen Display of the Detailed Calculations of 

OH Radical Addition to the Aromatic Ring. 

OH Addition to Aromatic Rings 

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

de+ = Most negativs value of ep+ or em+ (-C=C **l = 

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** 

.020 

Press any key to continuE 

-27-
Figure 6. Atmospheric Oxidation Program Data Display for the 

Compound a-Methyl Styrene (2-Phenyl-1-Propene): 

Screen Display for OH Addition to the Aromatic Ring 

and the Experimental Data. 

DH Addition to Aromatic Rings 

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

de+ = Most negativ~ valus of ep+ or em+ (-C=C **) = 

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

Ring #1 Kar = 1.9187 E-12 cm31molecule-sec 

1.9187 E-12 cm3/mol~cule-sec 

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

.020 

ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD? 

3' 

'3 Name: 2-+'heny l-1-pt~opene (~-methyl styt-·ene) 

J CAS Number: 00098-83-9 

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

3 Exper Ozone rate constant cm3/molecule-sec 

3 Exper N03 rate constant cm3/molecule-sec 

.3 

3 

7 

·..J 

3 3 

3 3 

@DDDDDDDDDDDDDDDDDD4 Press any key to continue ..• CDDDDDDDDDDDDDODDDDDYe 

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

styrene. 

IV. Evaluation of the Atmospheric Oxidation Computer Program 

for Estimating koa and the Experimentally Measured koa 

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<) = 

o.ooo 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 

-29-
Table 1. Group Rate Constants for Hydrogen Abstraction and 

Radical Reaction1 

Group Rate. Constant k X 1012 cm3/molecule-sec 

k(-CH3) 0.144 

k(-CH2-) 0.838 

k(>CH-) 1.83 

k(>C<) 0 

k(-OH) 0. 0362 

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-N02) 0 

k[P(=O)] 0 

k[P(=S)] 55 

1 Data from Table 1 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 

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

2 This group rate constant is only applicable to hydroxyl groups in alcohols and glycols. 

3 Used 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 Abstraction1 

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

Substituent 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. -CH20N02 0.30 

8. -CH2CN 0.5 

9. -CH2I ** 0.57 (given aame value aa -CH2Br) 

10. >CH- 1.29 

11. -CHCL2 0.57 

12. -CHF2 .0.10 

13. -CHBr2 ** 0.57 (given same value a a -CHCL2) 

14. -CHI2 ** 0.57 (given same value as -CHCL2) 

15. >CHC(.O)- 4.4 

16. >CHON02 0.30 

17. >C< 1.29 

18. -CCL3 0.09 

19. -CF3 0.075 

20. -CBr3 ** 0.09 (given same values as -CCL3) 

21. -CI3 ** 0.09 (given same values as -CCL3) 

22. >CC(•O)- 4.4 

23. >CON02 0.30 

24. -CF2CL 0.025 

25. -F 0.099 

26. -CL 0.38 

27. -Br 0.30 

28. -I ** 0.30 (given aame value as -Br) 

29. •0 8.8 

30. -Aromatic 1.0 

31. -OH 3.4 

32. -o- 6.1 

33. -ON02 0.18 

34. -CN 0.14 

35. -OC(•O)R 1.5 

36. -C=(O)CL 0.5 

37. -C(=O)- 0.76 

38. -CHO 0.76 

39. -C(•O)OR o.o 

40. >C•C< 1.0 

41. -C•C- 1.0 

42. -SH 9.0 

-31-
Table 2. Continued 

Substituent 

43. -s44. -ss45. -NH2 

46. -NH47. -N< 

48. -NNO 

49. -NN02 

so. -N02 

51. -OP52. -SP53. -P- ** 

54. •P ** 

ss. •N ** 

56. •S ** 

57. CH-Halogen ** 

58. S(+4)•0 ** 

59. blank 

60. Missing 

61. -cH-2Halogens ** 

62. -C-3Halogens ** 

63. -CHP-Halogen ** 

64. -o-o- ** 

65. -O-N• ** 

66. >CN02 ** 

67. >CHN02 ** 

68. CH2-N02 

69. CH2-0-

70. 2nd -o71. Sulfonic acid ** 

72. 2nd alkyl ketone 

73. -CH(Halogen)C•O ** 

74. -CH(N02)C•O ** 

75. -CH(N02)Halogen ** 

76. >e ( N02 ) c-o- ** 

77. >C(ON02)C•o- ** 

78. -CH(ON02)C-o ** 

79. >C-0- ** 

Factor 

9.0 

9.0 

10 

10 

10 

10 

10 

0.18 

20 

20 

1.0 

1.0 

1.0 

9.0 

0.57 

99.0 

1.0 

0.0 

0.57 

0.09 

0.30 

so 

2.0 

0.30 

0.30 

0.30 

4.50 

1.00 

0.20 

1.00 

3.10 

1.3 

0.21 

1.3 

1.3 

1.3 

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 #a 42, 43, 44) 

(estimated by Asa Leifer) 

(baaed on dimethyl sulfoxide data) 

(given same value as -CHCL2) 

(given same value as -CCL3) 

(assigned a value between -CHF2 and 

-CHCL2) 

(baaed 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 CH2-0-) 

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

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

-32-
•• 

Table 3. Factors Used for Aliphatic Ring Strain Effects1 

Factor 

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 

1 Data from Table 10 in Group Rate Constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan {1990b)]. 

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

have any ring strain effect factor applied to them. 

-33-
Table 4. Group Rate Constants for OH Radical Addition to 

Isolated Olefinic Units1 

structure k x 1o12 cm3;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 

1 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-

.. 
... Table 5. Group Rate Constants for OH Radical Addition to 

Conjugated Olefinic Units1 

No. Alkyl Groups 

1 

1 

Structure 

CH2=CH-CH=CHCH2=CH-<f=CH2 

k X 1012 cm3jmolecule-sec 

105 

105 

----------------------------------------------------------------- 2 CH2=CH-CH=C< 135 

2 CH2=CH-<f=CH- 135 

2 CH2=<f-CH=CH- 135 

2 -CH=CH-CH=CH- 135 

2 CH2=y-<f=CH2 135 

----------------------------------------------------------------- 3 CH2=CH-y=C< 180 

3 CH2=y-CH=C< 180 

3 -CH=CH-CH=C< 180 

3 CH2=y-y=CH- 180 

3 -CH=CH-y=CH- 180 

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

-35-
Table 5. Continued 

No. Alkyl Groups Structure k X 1o12 cm3/molecule-sec 

4 >C=CH-CH=C< 230 

4 -CH=C-CH=C< 230 I 

4 -CH=CH-C=C< 230 I 

4 CH2=C-C=C< 230 I I 

4 -CH•C-C-CH- 230 I I 

----------------------------------------------------------------- 5 >C=C-C=CH1 I 

5 >C=CH-r=C< 

----------------------------------------------------------------- 6 >C=r-r=C< 

1 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 Units 1 

Structure k X 1012 cm3fmolecule-sec 

CH•C- 6.4 

-esc- 29.0 

1 Data from Table 3 in Group Rate constants and Substituent 

Values Used by the Atmospheric Oxidation Program, Version 1.30, 

November 1990 [Meylan (1990b)]. 

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

1,2-Dialkene (Allene) Units1 

Structure k x 1o12 cm3tmolecule-sec 

CH2=C=CH- 31.0 

-CH=C=CH- 57.0 

CH2=C•C< 57. o2 

-CH=C=C< 85. o2 

>C=C=C< 110. o2 

1 Data from Table 4 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 •••• 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 

Olefine and Acetylenes1 

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

Substituent Factor 

l. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

29. 

30. 

31. 

-F 

-CL 

-Br 

-CH2CL 0.76 

-eN 

-CHO 

-C{•O)CH3 

-OCH3 

•0 

-I ** 0.26 

-CH2Br ** 

-CH2!' ** 

-CH2I ** 

-c-c ** 

not used 

-Phenyl ** 

-C(.O)X ** 

-oc ** 

-c•c ** 

-s ** 1.0 

-o ** 1.0 

-P ** 1.0 

-N02 ** 

-ON02 ** 

•S ** 1.0 

-N ** 0.6 

•P ** 1.0 

•N ** 1.0 

cyclic c-o 

Miaainq 

R 

** 

0.4 

0.20 

0.26 

0.15 

0.26 

0.91 

1.3 

1.0 

{qi~en same value as -Br) 

0.76 {qiven same value as -CH2CL) 

0.76 {qiven same value as -CH2CL) 

0.76 {qiven same value as -CH2CL) 

0.85 

1.0 {Atkinson assumption, Int. J. Cham. Kinet. 19:822.) 

0.91 {given same value as -C(•O)CH3 

1.3 (given same value as -ocH3) 

1.10 {baaed on experimental rate constant for 

diacetylene) 

{arbitrarily aaaiqned a value of unity) 

{arbitrarily aaaiqned a value of unity) 

{arbitrarily assigned a value of unity) 

0.5 (arbitrary estimate) 

0.6 (arbitrary estimate) 

(arbitrarily aasiqned a value of unity) 

{arbitrary estimate) 

{arbitrarily assiqned a value of unity) 

{arbitrarily aaaiqned a value of unity) 

0.20 {baaed on data for naphthaquinone) 

1.0 

1.00 {for an alkyl or a cycloalkyl qroup) 

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

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

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

Addition to Aromatic Rings1 

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

The ~ and ~ values which are ~ considered "assumed" values are taken 

directly !rom th.following reference: Brown, H.c. and Okamoto, Y (1958), 

"Electrophilic Substituent Constanta", J. Am. Chern. Soc. 80: 4979-4987. 

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

~ a; 

1. Amino (-NH2) -0.16 -1.3 2. Dimethyl amino (CH3-N-CH3) -0.16 ** -1.7 3. Aniline (C6H5-NH-) -0.16 ** -1.4 4. Acetyl amino (CH3C(•O)-NH-) 0.21 ** -0.6 5. Benzoyl amino (C6H5-C(=O)-NH-) 0.21 ** -0.6 6. Hydroxy (-OH) 0.121 ** -0.92 7. Methoxy (-OCH3) 0.047 -o. 778 a. Phenoxy (C6H5-0-) 0.10 ** -0.50 9. Methylthio (CH3-S-) 0.158 -0.604 10. Methyl (CH3-) -0.066 -o. 311 11. Ethyl (CH3-CH2-) -0.064 -0.295 12. Isopropyl (CH3-CH-CH3) -0.060 -0.280 13. tart-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 (-N02) 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 (-ON02) 0.674 ** 0.790 ** 30. Olefinic (-C•C) 0.02 ** 0.02 ** 31. Acetylenic (-C•C) 0.21 ** 0.23 ** 32. -O-R (assume methoxy) 0.047 ** -0.778 ** 33. Phoaporua (-P) o.o ** 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 

~ a; 

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. -0-C(•O)- 0.10 ** -0.10 

so. Undefined o.o ** o.o 

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 SS-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 rata constants for PCBs. 

ss. -C6H4-Xl 0.25 ** 0.02 

56. -C6H3-X2 0.39 ** 0.22 

57. -C6H2-X3 0.53 ** 0.42 

sa. -C6Hl-X4 0.67 ** 0.62 

59. -Phanyl-XS 0.81 ** 0.82 

60. -503 0.50 ** 0.50 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

** 

61. -S•O -0.16 ** -1.30 ** 

1 Data from Table 8 in Group Rate Constanta 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) = 

o.ooo, 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-Cl) = o.oo; and this should be added to Table 1 and to the 

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

k(>N-N02), and k[P(=O)] should be listed as o.oo. 

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 koH for acyclic and cyclic sulfides and compares the 

estimated values with the experimental values6 • For example, for 

dimethyl sulfide, the recommended experimental value of koH from 

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

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

experimental value should be qualified to indicate that koH was 

5 It should be noted that for convenience, the factor 

1o-12cm3molecule-ls-1 has 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 

koH will be written without the factor 1o-12cm3molecule-1s-1. 

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

vs. PCFAP." 

-42-
.. -

obtained from measurements in the absence of oxygen. If one 

wants to compare the estimated value with the experimental value, 

then koa should be estimated under the boundary condition in the 

absence of oxygen and koa = 2.59 [since k(-S-) = O.OO]. 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)3 and the footnote 3 at the bottom of this 

table should be 3 Applicble 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-) = o.oo. 

This is discussed in more detail in Section IV.E.1.b. 

From the experimental koa data of diethylhydroxylamine, it 

was found that k(>NOH) = o.oo [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-
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 k08 for carboxylic acids and 

Section IV.C.4.b. for the discussion of the estimation of k08 for 

alkyl peroxides. 

In Table 2, item, No. 57, should be changed to F(R2CHC1) = 

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

dichlorobutane from Millet 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 

koH data 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 a, 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 koH data, then the symbol ** should be omitted. For 

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

substituent factor is listed as {C[-C•C-**]} = 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 a. 

Therefore, for the substituent factor C[Cyclic C=O **] (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 koH data of styrene, a- and ~-methyl styrene, 

and P-dimethyl styrene [Atkinson (19a7, page a2a)]. These 

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

** in Table 2. 

In Table a, No. 14 is listed as C(C•C- **) = o.a5 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 a~ value for substituent -cH2- (No. 

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

However, a~ 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'), AOP uses equation 24; for fused 

ring polynuclear aromatic hydrocarbon compounds (PAH), AOP uses 

equation 29; and for fused ring polynuclear heterocyclic 

I 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 koH for 

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 11 list the values of Ai and Bi, 

respectively, for various heteroaromatic ring structures and 

polyaromatic hydrocarbons derived from the experimental koH data 

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

values of Bi and ai , 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 

Fur an 

Thiofuran 

Imidazole 

oxazole 

Thiazole 

Pyridine 

1,3,5-Triazine 

Experimental Value of Ai 

{1o-12cm3molecule-1s-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-
Table 11. Experimental Values of Bi for Some Polynuclear Aromatic Compounds* 

Polynuclear Aromatic Rinq Structure 

Naphthalene 

Anthracene 

Phenanthrene 

Experimental Value of Bi 

(1o-12cm3molecule-1s-1) 

21.6 

110.0 

31.0 

* Data from paqe 7 of the User's Guide for the Atmospheric oxidation Proqram, ·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 

(1o-12cm3molecule-1s-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-
Table 13. Values of Bi for Polynuclear Heteroaromatic 

Structures Derived from Experimentally Measured 

Ionization Potentials* 

I Assigned Value of Bi 

Based on the Experimentally Measured 

Ionization Potential 

Polynuclear Heteroaromatic structure (1o-12cm3molecule-1s-1) 

Quinoline 

Isoquinoline 

Quinoxaline 

Quinazoline 

Acridine 

6.5 

6.5 

2.0 

2.0 

27.5 

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

Oxidation Program, Version 1.10, November 1, 1990 [Meylan (1990b)]. 

-so-

- ... 
.. -

factors a~ and a~ 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 

k08 for benzothiazole. In principle, however, the basic 

concepts of Meylan can be used. For example, if k08 is 

measured for benzothiazole, then Bi from equation 30 can be 

determined. Therefore, with this value of Bi, k08 can be 

estimated for substituted benzothiazoles utilizing the 

appropriate substituent factors a+ m and a+ p for the substituents 

on the ring. 

More experimental k08 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, 11, 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.1.a. Evaluation of the Experimental koH Data 

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

koH 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 koH at 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 

-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 koa Data Reported in the Literature Versus the 

Experimental koa Data Reported in AOP 

1o12koH(cm3molecule-1s-1) 

I Chemical Experimental Estimated 

AOP (a) AOP HC 

Methane 9-t/-8,;:;-11 0.00841 0.00836* 0.00841b (c) 

Ethane ?'-1- '?L/-0 0.268 0.268* 0.288 0.288 

Propane 7 Lf .<:j '? ~ 1.15 1.15* 1.21 1.21 

n-Butane /0~- 97·· s:=' 2.54 2.54* 2.53 2.53 

2-Methylpropane 1S-;)..g-s- 2.34 2.34* 2.39 2.39 

n-Pentane I09-Co0-0 3.94 3.94* 3.93 3.93 

2-Methylbutane ::; 15-'if ff -f-j 3.90 3.9* 4.00 4.00 

2, 2-Dimethylpropane '/b3 -K2-J 0.849 0.849* 0.743 0.743 

n-Hexane 110-S'-/- 3 5.61 5.61* 5.32 5.32 

2-Methylpentane IO"f-1]3-$"' 5.60 5.6* 5.39 5.39 

3-Methylpentane CJ~-ILj- 0 5.70 5.7* 5.77 5.77 

2, 2-Dimethylbutane 15-83-2. 2.32 2.32* 1.82 1.83 

2, 3-Dimethylbutane 1'1- ;;lC}-~ 6.20 6.2* 5.46 5.46 

n-Heptane 1'1-:J- ~;2 -s 7.15 7.15* 6.72 6.71 

2, 2-Dimethylpentane S'JO- .3S-~ 3.37 3.37d 3.22 3.22 

2, 4-Dimethylpentane ;o 6'-o8-"f- 5.16 5.16d' 6.86 6.85 

2, 2, 3-Trimethylbutane~~- 0~-2.. 4.23 4.23* 3.29 3.30 

n-octane /1/-~5 -, 8.68 8.68* 8.11 8.11 

2, 2-Dimethylhexane 590- 73- S' 4.83 4.83d 4.61 4.61 

2, 2, 4-Trimethylpentane 5'-/o-8Lj-l 3.6, 3.68* 4.68 4.68 

2,3,4-Trimethylpentane 7.0 6.97e 8.70 8.70 

SfoS-15-3 ' ~ 

j 

I 

-53-
Table 14.A. continued 

1o12koH(cm3molecule-1s-1) 

Chemical Experimental Estimated 

5'14- g d.-1 cs H l'i? ~I AOP (a) AOP 

2,2,3,3-Tetramethylbutane 1.08 1.08* 1.11 

n-Nonane Ill -f{t.j-;J.. 10.20 10.2* 9.51 

2-Methyloctane 3;Jc;J J-~1-;;.. 10.1 10.1d 9.58 

4-Methyloctane ;):JJ~- 31-'1 9.72 9.72d 9.95 

2,3,5-Trimethylhexane /u~~-o3-0 7.88 7.88d 10.1 

n-Decane /;}'-/- If?-~ 11.6 11.6* 10.9 

n-Undecane /!d. O- d)/ -J.j Cll H jq 13.2 13.2* 12.3 

n-Dodecane JJ()- Ljo-3 14.2 14.2* 13.7 

n-Tridecane &9-9-So-s- 16.0 16* 15.1 

n-Tetradecane ~,JCj- 59- i 19.2 19.2* 16.5 

n-Pentadecane ~~9- c.:,~ -cp 22.2 22.2f 17.9 

n-Hexadecane 5tf1- 'ftJ-3 24.9 24.9f 19.3 

a Experimental 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 Experimental value from Behnke et al. (1988). d' Experimental value from Atkinson et al. (1984). 

e Experimental value from Harris and Kerr (1988). f Experimental value from Nolting et al. (1988). 

-54-

HC 

1.11 

9.50 

9.58 

9.95 - 10.1 

10.9 

12.3 

13.7 

15.0 

16.5 

17.9 

19.3 
• 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 

- 1 

~ I ( 0 

" ..( 

I ( ..$) 

~ 

1o12koH(cm3molecule-1s-1) 

Chemical Experimental Estimated 

AOP (a) AOP HC 

cyclopropane 9~- /~- Lj 0.07 0.071b 0.0711 0.0711 

.i-Propylcyclopropane U1fo- ;;9:: r 2.84 2.84c 2.85 2.85 c •'If< t&> 1.2d Cyclobutane r!) &>1-- 2 3-D 1.20 1.23 1. 23 

cyclopentane [)8 7- ~;)._- 3 5.16 5.16* 5.58 5.58 

Cyclohexane I IO- Ba.- -=f" 7.49 7.49* 8.37 8.37 

Methylcyclohexane 1 o ~ -g 7- ~ 10.4 10.4e 10.2 10.2 

1,1,3-Trimethylcyclohexane 3 8.73 8.73f 9.18 9.18 

30f'O-(t?&:,-

12.5g Cycloheptane ~4/-t,I./-S' 12.5 9.76 9.77 

cyclooctane d-'J;) -V; Lf-&> 13.7 13.7h 11.2 11.2 

Bicyclo [2.2.1] heptane 219-23-2 5.49 5.49i 9.49 9.49 

Bicyclo [2.2.2] octane z&-o- 33-1 14.7 14.7i 16.2 16.2 

Bicyclo [3.3.0] octane~9£,- 'l.l-1 11.0 11.oi 10.4 10.4 

$Pii 17.2i ili-Bicyclo [4.3.0] nonane 17.2 14.1 14.1 

trans-Bicyclo [4.3.0] nonane 17.6 17.6i 14.1 14.1 

£1a-Bicyclo [4.4.0] decane 19.9 19.9i 19.0 19.0 t/9~- OI-l Uo/-itS" 20.4i trans-Bicyclo 4.4.0] decane 20.4 19.0 19.0 

L{q_3- ?f-'1 ctui-PS, 

11. 3i Tricyclo [5.2 •• o u] decane 11.3 12.3 12.3 

r; oa..;- 3!S -,..< ool-l ;;._. 

22.6j Tricycle [3.3.1.1 ~] decane 22.6 24.1 24.1 

.;73/-"'3 -co< C/ofll& 

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) • 

i Experimental value from Atkinson, Aschmann, carter (1983a). 

j 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. 

-55-
each recommendation. These recommended values have an asterisk 

after each value. 

In general, the experimental values of k08 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 k08 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 

significant figures. 

It should be noted that the names of two tricyclic decanes 

{tricycle [5.2.1.0] decane and tricycle [3.3.1.1] decane} entered 

in AOP are incorrect. The correct names should be tricycle 

( 5. 2 .1. 0 2•

6 ] and tricycle ( 3. 3 .1.1 3•

7 ] decane since the 

superscript numbers on the last digit must be specified to 

identify the bridgehead carbons on the last ring. Finally, the 

-56-

> .. 
-. name of methylcyclohexane is the correct name and not 

1-methylcyclohexane as listed in AOP. 

IV.C.1.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 koa in AOP was 

incorrect. The AOP computer program did not use the ring strain 

factors [F(J), F(4), F(S), or in Meylan's notation RSJ, RS4, RSS) 

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 koa by 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 

koa with a maximum of six significant figures and the detailed 

calculations list k(1a) or k(1c) with a maximum of five 

significant figures. However, the group rate constants k~, k~, 

and k~, [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(1a) or k(1c), or k(1a) + k(1c), and koa 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 koH 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 RSS 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-) (RSS) (RSS) 

- 0.838(1.29) {1.29) (0.64) 

- 0.892 

It seems to me that a more consistent notation for RSS would be 

(RS5)2 • (0.80)2 rather than {RSS) (RSS) = 0.64. Therefore, ksec 

-sa-
should read 

or 

ksec.= 0.838 F(-CH2-)F(>CH-) (RS5)2 

= 0.838 (1.29) (1.29) (0.80)2 

= 0.892 

ksec • 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 koH 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 

Experimentalf(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 1o-12cm3molecule-1s-1 rather 

than 1o-14cm3molecule-1s-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-
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 ~n AOP 

1o14koH(cm3molecule-1s-1) 

/ Chemical Experimental Estimated 

AOP (a) AOP HC 

Fluoromethane S93- S3- ~ 1. 68 1.68* 1.43 1.43 

Chloromethane 11~~1-3 4.36 4.36* 5.47 5.47 

Bromomethane ?4-83-~ 4.02 4.02* 4.32 4.32 

Difluoromethane 15-;o-s- 1.09 1.09* 0.82 0.821 

Fluorochloromethane 5~3-ro-1 4.41 4.41* 3.15 3.15 

Dichloromethane ~~-09~~ 14.2 14.2* 12.1 12.1 

Trifluoromethane 15" -4&-r 0.024 0.024b 0.18 0.178 

Difluorochloromethane 1-S' ~5"-62 0.468 0.468* 0.682 0.682 

Fluorodichloromethane 15""- J/?ri 3.03 3.03* 2.62 2.62 

Tr !chloromethane u "1 - ~ - 3 10.3 10.3* 10.0 10.0 

Fluoroethane 35 3 -.%- <o 23.2 23.2° 20.5 20.5 

Chloroethane 1 S -oo- 3 39 39* 40.1 40.0 

1,1-Difluoroethane 15-3-=J-u, 3.4 3.4* 3.23 3.23 

1, 2-Difluoroethane &J Lj ... 7~ -&; 11.2 11.2d 14.1 14.1 

1, 1-Dichloroethan~ys- :3 L/- 3 26 26.oe 34.6 34.6 

1, 2-Dichloroethane I 0 r-Ob -cJ 22 22.oe 36.3 36.3 

1, 2-Dibromoethane lot.,- 93-1- 25 25.oe 28.7 28.7 

1,1,1-Trifluoroethane~~o~~-~ 1.7 0.171d 1. 08 1. 08 

1, 1, 1-Trichloroethane 11-SS-(., 1.19 1.19* 1.30 1.30 

1,1-Difluoro-1-chloroethane 0.358 0.358* 0.36 0.360 ~s-CP;t-.3 1, 1, 2-Trifluoroe nane 1Jo-h6-o 1.8 1.83d 2.35 2.35 

1,1, 2-Trichloroethane ::JC)- oo-s- 32.8 32.4f 33.2 33.3 

1,1,1,2-Tetrafluoroethane 0.854 0.854* 0.62 0.622 8//- 9~-d. 

1-Chloro-2,2,2-Trifluoro- 1.62 1. 62* 2.39 2.39 

ethane -:rs-'8;8- r 

1,1,2,2-Tetrafluoroethane (j) 0.679 0.36 0.359 359- 3s-3 

-60-
) " 

• Table 15. Continued 

1o14koH(cm3molecule-1s-1) 

Chemical Experimental Estimated 

~ AOP (a) AOP HC 

Pentafluoroethane 35'1-.33-& (.~I/ Fs- 0.25 0.249d 0.13 0.135 

1-Chloro-1,2,2,2-Tetrafluoroethane 1.02 1.02* 0.52 0.516 OJ83~ ~!j;9-0 C~I-/C) Ff 3.35 3.35* 1.98 1.98 1,1-0ichloro- 1 2,2-Trifluoroethane 

3oeo- g3-,;1. c;JI-fCf:2F3 

43.5k 1,2-0ibromo-3-chloropropane~-/~-g 44 50.3 50.3 

2-Chlorobutane =/8-8b-"L/ (.. 31-+5 Bli';~ CJL (j) 230i 164 164 

2, 3-0ichlorobutane 15'8 J- 91-1- (j) 96i 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). 

i Experimental value from Millet 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-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 koH Data 

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 koH by HC 

is 0.178, while AOP rounds it off to 0.18. 

IV.C.J. Carbonyl Compounds 

IV.c.J.a. Evaluation of the Experimental koH Data 

Table 16 summarizes the pertinent experimental koH data 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: 11 aldehydes, 19 ketones, 3 a-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 koH data 

with two significant figures. If the original literature sources 

and Atkinson {1989) are checked, all the koH data are listed with 

three significant figures (e.g., formal, 3-hexanone, n-butyl 

-62-
• 

, , 

Table 16. Comparison of the Estimated Values of k08 at 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 k08 Data ~n AOP 

1o12kou(cm3molecule-1s-1) 

Chemical Class/Chem~l Experimental Estimated 

AOP (a) AOP(%Error) 0 HC 

A. ALDEHYDES 

Formal so-oo-o 9.7 9.77* 7.37 7.37 

Ethanal ·?s-o '1-0 15.8 15.8* 16.2 16.2 

Propanal ;2?r38 -& 19.6 19.6* 22.0 22.0 

Butanal iJ3- (.2-? 23.5 23.5* 25.5 25.5 

2-Methyl Propanal 16-~~-~ 26.3 26.3* 23.4 23.4 

Pent anal 110 -& ,')- _3 28.5 28.5* 27.6 27.6 

3-Methylbutanal sqo- ~b- 3 27.4 27.4* 30.0 30.0 

2, 2-Dimethylpropanal t.:b- /9 -J 26.5 26.5* 22.7 22.7 

Trichloroacetaldehyde 1ji-~?-w 1. 73 1. 73a' 1.45 1.45 

Hydroxyethanal I '/I-· -9'<::, ~?f 9.9 9.9b 23.0 23.0 

(Glycolaldehyde) 

Pentane-1, 5-Dial I I 1- 3o-e' 23.8 23.8c 46.9 46.9 

B. ACYCLIC KETONES 

Propanone & ?-u~l- I 0.226 0.226* 0.219 0.219 

2-Butanone 78- 'j,3- _'3 1.15 1.15* 1. 38 1.38 

2-Pentanone /u-:;-s-J-9 4.9 4.9* 4.80 4.81 

3-Pentanone 9 (.,- cx7:) --tJ 2.0 2.0* 2.54 2.55 

2-Hexanone !;C)J- -=f8-~ 9.1 9.1* 6.95 6.96 

3 -Hexanone 589- 38-fi' 6.9 6.9od 5.97 5.97 

4-Methyl-2-pentanone /'-1/-79- j- 14.1 14.1* 9.35 9.35 

3, 3-Dimethyl-2-butanone ls-q:r-<J 1.21 1.21e 2.01 2.01 

2-Heptanone l!o-~3-o 8.67 8.67e 8.35 8.35 

-63-
Table 16. Continued 

Chemical Class/C~ical Experimental 

AOP 

VI 505-go~o 

2,4-Dimethyl-3-pentanone 5.38 

2 -octanone J I/- I 3 -'f 1 o • o 

2-Nonanone 8~}- 55-(a 12.2 

2, 6-Dimethyl-4-heptanona'CB'-&}-8' 27.5 

2-Decanone ~ 93-- SL/-cp 13.2 

2, 4-Pentanedione /~ 3- 5 ¥-eo 1.15 

2, 5-Hexanedione 110-13-1 7.13 

C. CYCLIC KETONES 

cyclobutanone 1 /c."JI-c:JS- ~ 

cyclopentanone / GJo- 9rJ-- 3 

Cyclohexanone /08- c::J'f- 1 

D. a-DICARBONYLS 

Glyoxal 1 o 1- ,.J;J- ,::;.., 

Methylglyoxal 7~- ':1~-'? 

Biacetyl L/-31- 03-8 

E. ACYL CHLORIDES 

Acetyl chloride 75- 3(o-sF. ESTERS 

Methyl formate /OT-31-3 

0.87 

2.94 

6.39 

11.4 

17.2 

0.238 

0.068 

0.23 

-64-

(a) 

5.38d 

11.0e 

12.2e 

27.5* 

13.2e 

1.15f 

7.13f 

11.4* 

17.2* 

0.238* 

0.0689 

Estimated 

AOP(%Error) 0 HC 

5.32 

9.74 

11.1 

18.5 

12.5 

0.703 

5.82 

1.17 

8.92 

12.6 

24.5 

12.3 

0.219 

0.0720 

0.216 

5.31 

9.74 

11.1 

18.5 

12.5 

0.703 

5.82 

1.17 

8.92 

12.6 

24.5 

12.3 

0.219 

0.0720 

0.216 
Table 16. Continued 

Chemical C~~/Chemical 

Ethyl formate /09-9L/-'f 

n-Propyl formate 1/Q- =fl../-7-

n-Butyl formate 5~£). - 8£j- r 

Methyl acetate -=f~-t..o-0; 

Ethyl acetate lt../J-78-0 

n-Propyl acetate tcf1-(o0-4 

i-Propyl acetate I o?J-.:1._ 1-'-/ 

n-Butyl acetate f(}. 3-Bfo-l.j 

.§l-Butyl acetate ;os-'-fto-4 

Ethyl propionate I CJ5-3 r 3 

n-Propyl propionate 101-1-3~-S 

Methyl butyrate (.p&3- tp- rEthyl buty,frate loS- 5'-/-i--

n-Propyl butyrate /o5-tato-~ 

n-Butyl butyrate f'oiJ- ~ )- qEthoxyethyl acetate ;//-;S-9 

Methyl trifluoroacetate '-/31-tJ--=t- 0 

G. CARBOXYLIC ACIDS 

Formic acid ~-18-~ 

Acetic acid & '-/- /9 -1-

Propionic acid -::f9-o9-1 

n-Butyric acid /61--9'2-:- ((, 

i-Butyric acid ':fC}-3/- 2..._ 

Experimental 

AOP 

1.0 

2.4 

3.1 

0.34 

1.6 

3.4 

3.4 

4.2 

(n) 

2.1 

4.0 

3.0 

4.9 

7.4 

10.6 

13.0 

0.05 

0.45 

0.74 

1.22 

2.4 

2.00 

(a) 

1.02h 

2.38h 

3.12h 

0.341i 

1.6* 

3.4* 

3.4* 

4.2* 

5.5* 

2.14i 

4.02h 

3.04h 

4.94h 

7.41h 

10.6h 

13h' 

0.052h 

0.45* 

0.741 

1.221 

2.4m 

2.ool 

Estimated 

AOP(%Error) 0 

1.44 

2.89 

4.28 

0.216 

1.44 

2.89 

3.12 

4.28 

4.99 

1.63 

3.08 

1.48 

2.71 

4.16 

5.55 

14.0 

0.216 

0.436j(-3) 

0.145(-80) 

0.859(-30) 

2.12(-12) 

1.80(-10) 

HC 

1.44 

2.89 

4.28 

0.216 

1.44 

2.89 

3.12 

4.28 

4.99 

1.63 

3.07 

1.48 

2.71 

4.16 

5.55 

14.0 

0.0518 

(k) 

(k) 

(k) 

(k) 

(k) 

a Experimental values from Atkinson (1989) and the literature. 

a' . Exper1mental value from Nelson et al. (1984) as reported by Atkinson 

(1989). 

-65-
Table 16. continued 

b Experimental value from Niki et al. (1987) 

c Experimental data from Rogers (1989). This value of koa represents the average value of 25.2 and 22.4x1o-12cm3molecule-1s-1 as 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). 

i Experimental value from Wallington et al. (1988). The data from campbell and Par~inson (1978) was not used since the experimental method was probably . not valid/Atkinson (1989)]. J Estimated by [Meylan (1990b)] assuming that k(HCOOH **) was 0.400. k Atkinson did not develop S/R relationships for carboxylic acids. 1 Experimental 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 5.5x1o-12cm3molecule-1s-1 is given in the document "Estimated Accuracy of AOP versus PCFAP. 

o Based on the experimental values of koij listed in column Experimentalf(a). * Recommended value by Atkinson (1989) w1th 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 koH of 10.0 while Wallington and Kurylo (1987) and Atkinson 

(1989) list a value of 11.0. For §-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 

n- and i-butyric acids as obtained from Atkinson (1989) and the 

literature. The koH data from Zetzsch and Stuhl (1981) for 

acetic, propionic, and n-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 

koH 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. 

-67-
IV.C.J.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 

i~ 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 g~oup -cF3 on the substituent factor 

F[-OC(O)R]. Leifer (1991a) derived a substitutent factor 

F(-OC(O)CFJ] = 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, 

-68-
R(=O)OH + ·OH k(1) = k(1a) I ·R C(=O)OH + HOH (32) 

RC(=O)OH + ·OH 

k(2) = k(-OH) RC(=O)O· + HOH (33) 

where R' is an alkyl free radical [i.e., ·R' or for formic acid, 

it is ·C(=O)OH]. The overall rate of reaction with hydroxyl 

radicals is then 

koH = k(1) + k(2) = k(1a) + k(-OH) (34) 

and Meylan assumed that reaction pathway 32 was the dominant 

pathway [i.e., k(1a) > k(-OH)]. Therefore, Meylan used the group 

rate constant k(-OH) = 0.036, derived from the alcohols; and the 

rate constant k(1a), 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(1a) = k[HC(=O)OH ** ] = 0.400 (35) 

so that 

koH (formic acid, estimated) = 0.436 (36) 

and this result is listed in the fourth column of Table 16. The 

values of koH (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 koH 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 koH 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(O)OH and 

DC(O)OH and OD radicals with HC(O)OD and DC(O)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(=O)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 koa 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 koa data 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 

koH data of Zetzsch (1985) and Edney et al. (1986) assuming that 

koH = 0.55 of Edney. 

IV.C.4.b. Evaluation of the Estimated koa Data 

Comparison of the estimated values of koa 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-
Table 17. Comparison of the Estimated Values of koH at 298 K for Alcohols, 

Glycols, Ethers, and Hydroperoxides 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 

1o12koR(cm3molecule-1s-1) 

Chemical Class/ChemiJal Experimental Estimated 

AOP (a) AOP(tError)m HC 

A. ALCOHOLS 

Methanol t;:::; -5~- I 0.932 0.932* 0.526 0.526 

Ethanol &if -;:;-s- 3.27 3.27* 3.07 3.08 

1-Propanol =11- 0! 3-3 5.34 5.34* 4.98 4.99 

2-PropanofX 5.21 5.21* 6.63 6.63 

1-Butanol 11- 'lt1- 3 8.3 8.31b 6.37 6.38 

2-Methyl-2-Propanol w7- & -::t> ~ 0 1.12 1.12* 0.593 0.593 

1-Pentanol :::JI-41-o 10.8 10.8° 7.77 7.77 

2-Pentanol (/;o-?;~-.2'7- =t- 11.8 11.8d 10.9 10.9 

3-Pentanol ~'9~ -(.);;J -I 12.2 12.2d 12.9 12.9 

3-Methyl-2-butanol 5<78-75 4 12.4 12.4d 11.0 11.0 

1-Hexanol /11-J-9-- ~ 12.4 12.4d 9.17 9.17 

2-Hexanol /.p;)~- CJ ?rT 12.1 12.1d 12.3 12.3 

1-Heptanol 111- =fo-(o 13.6 13.6d 10.6 10.6 

2-Chloroethanol /07· 0 t- .3 1.4 1.4 2.07 2.07 

1-Hydroxy-2-propanone /~0_-o ~-~, 3.02 3.02e 2.31 2.32 ._3.H0u ._ 

Cyclopentanol C)tp- 41-3 10.7 10.7d 12.8 12.7 

B. GLYCOLS 

1, 2-Ethanediol SL/0- v3-(o 7.7 7.7 7.42 7.42 

1,2-Propanediol s:r--ss-eo 12.0 12 12.0 11.9 

-72-
.... 

Table 17. Continued 

1o12koH(cm3molecule-1s-1) 

Chemical Cla~Chemical Experimental Estimated 

AOP (a) AOP(%Error)m HC 

c. ACYCLIC ETHERS 

Dimethyl ether I I o- /O- C.O 2.98 2.98* 1. 76 1. 76 

Diethyl ether &a- 02 9-::r- 13.3 13.3* 11.5 11.5 

Di-n-Propyl ether I 11-i../3-3 17.2 17.2* 21.1 21.1 

Methyl-t-butyl ether /03'-l-oL/-L} 2.83 2.83* 2.82 2.82 

Methyl-n-butyl ether&<J8~ .~-'-/ 16.4 16.4d 13.6 13.6 

Ethyl-n-butyl ether6·o3- 81-9 18.1 18.1f 18.5 18.5 

Ethyl-t-butyl ether ~Pj/;; 2'S- 3 6.9 6.88f 7.70 7.20 

Methyl-t-amyl ether qCJJf-'05- S' 7.91 7.91d 6.13 6.13 

Di-n-butyl ether !'f~ ... 90- I 22.4 22.4f 25.5 25.5 

Di-i-butyl ether t~ c:l8 - ss- =r 26.0 26.0g 30.4 30.4 

Di-n-pentyl ether {o'jj- &.<J-d 34.7 34.7d 28.2 28.2 

1,1-Dimethoxy ethane~3~-~~-0 8.89 8.89e 13.1 13.1 

Diethoxymethane ~0- o;S- 3 16.8 16.8e 16.6 16.6 

1, 2 -Dimethoxypropane ff:f-'8- 85- 0 14.3 14. 3e 22.9 22.9 

2, 2-Dimethoxypropane 11-- .fto-~ 3.92 3.92e 3.05 3.05 

2, 2-Diethoxypropane /Jto-- 84- J 11.7 11.1e 12.8 12.8 

2-Methoxyethyl ether~~~ 17.5 17.5e 28.1 28.1 

f I 1- '10-(R { 01-/ j</0,~ 

1,1,3-Trimethoxypropane/~Y~-9~0 19.2 19.2e 28.5 28.5 

2-Ethoxyethyl ether X 26.8 26.8e 37.9 37.8 

Methoxy acetoneL5~ 1 g- I c;- ~) 6.77 6.77e 4.87 4.87 

2-Methoxy ethanol /o9-8'~- t.f 12.5 12.5e 11.2 11.2 

2-Ethoxy ethanol 1 ;0 - S'O- ::;- 15.4 15.4h 16.1 16.1 

3-Ethoxy-1-propanol /II- 35-3 22.0 22.oe 20.9 20.9 

3-Methoxy~1-butanolc2j/1-¥3-3 23.6 23.6e 20.6 20.6 

2-Butoxy ethanol 111-10 -,;;. 18.6 18.6h 23.0 23.0 

-73-
Table 17. Continued 

1o12koH(cm3molecule-1s-1) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP(%Error)m HC 

2-Hydroxyethyl ether /1!-L/r:._-- U. 

(Dihydroxyethyl ether) 30.0 30 20.6 20.6 

o. CYCLIC ETHERS 

Ethylene oxide 75--~1-~ 0.076 0.076* 0.224 0.224 

1,2-Epoxypropane (propylene 

oxide) ::t--s-- .Sto-9 0.052 0.52* 0.543 0.543 

1-2-Epoxy butane ( 1 t 2- _ 7- I &) -';5 tSButy lene oxide) '-'' tj If '1 o 2.1 2.1 1.69 1.69 · /<Jt:.-~-e 1-Chloro-2,3-epoxypropane 0.44 o.5oi 0.662 0.662 

Trimethylene oxide 503- 30 ... {) 10.3 10.3e 3.73 3.73 

Tetrahydrofuran I o9-99-9 16.1 16.1* 18.3 18.3 

1, 3-Dioxane s-o S-~a -~ 9.15 9.15e 22.1 22.1 

1,4-Dioxane /P?r-91-/ 10.9 10.9e 26.4 26.4 

1,3,5-Trioxane 1/0-i'iJ-3 6.2 6.2j 15.3 15.3 

Oxepane (Hexamethylene oxide) 

5"() - CJo -s15.4 15.4e 25.7 2.57 

E. ALKYL HYDROPEROXIDES 

Methyl hydroperoxide 3o3 I -13-0 5.54 5.54* 7.24(+31) (1) 

t-Butyl hydroperoxide 9'-/- Zw-€ 3.0 3.ok 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-
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). i Average value from the experimental data of Zetzsch (1980) and Edney et al. 

(1986) assuming koH = 0.55x1o-12cm3molecule-1s-1 of Edney. 

j Extrapolated 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 koij listed in column Experimentalf(a). 

• Recommended value by Atkinson (1989) w1th the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-75-
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 

koa data of methyl 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 k(1) = k(1a) ·R'cooa + 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 

k08 = k(1} + k(2} = k(1a} + 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(1a) and k08 were calculated in the standard manner. For 

methyl and ~-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 

Experimentalf(a}, were +31 and -34, respectively, and these 

-76-

... 
.. 

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 koH 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 16oH, 18oH, and 16oo radicals with cH3ooH and 16oo 

radicals with CH3ooo. 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, 

k(2) = k(-OH) 

k(1) = k(1a) 

( 41) 

(42) 

with the ·cH2ooH radical rapidly decomposing to give hydroxyl 

radicals and formaldehyde 

(43) 

The overall rate, from reactions 41 and 42, is 

koH = k(1) + k(2) = k(1a) + k (-OH) (44) 

-77-
Relative rate studies gives koH [= k(1a) + 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 16oH radical with ca3o16oa (or 16oo radical with 

CH3o16oo) gives the rate constant k(-OH). Furthermore, reaction 

of oo radicals with CH300H yields the overall rate constant 

koa [= k(1a) + k(-OH)] for the oo radical reaction. 

Atkinson (1989) carried out a unit-weighted least-squares 

analysis of the experimental data of Vaghjiani and Ravishankara 

(1989) for the reaction of 18oH and oo radical with ca3ooH over 

the temperature range 203-348K. Based on these data, Atkinson 

recommended the value of 

k(-OH) = 3.73 

at 298 K (in the units 1o-12cm3molecule-1s-1); from the 

experimental data involving 18oH and 00 radicals over the 

temperature range 223-423 K, Atkinson recommended a value of 

(45) 

k08 = 5.54 (46) 

at 298 K (in the units 1o-12cm3molecule-1s-1). Hence, 

k(1a) = 1.81 (47) 

and H-atom abstraction from the OH radical in methyl 

hydroperoxide is the major reaction pathway. 

-78-

1 • 
.. 

For t-butyl hydroperoxide, Atkinson (1989) indicated that 

because the C-H bonds in the CH3 group are stronger than the 0-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.s.a. Evaluation of the Experimental koa 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 

Nitrates 

of the Estimated Values of koH at 298 K for Alkyl ·~ 

and Alkyl Nitriles 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 

I 

~ 1o12koH(cm3molecule-1s-1) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP HC 

A. ACYCLIC NITRATES 

Methyl nitrate .St:;g>-~8- ~ 0.034 0.034b 0.0259 0.0259 

Ethyl nitrate~~~ ~8-/ 0.49c 0.49c 0.194 0.194 

1-Propyl nitratejt.JT·/3-1 0.67 0.67d 0.632 0.632 

2-Propyl nitrate 0.41 0.41e 0.416 0.416 

1-Butyl nitratej n-ALTYLivi!X:.lJ.ili' 1. 78 1.7ae 1. 79 1. 79 (jJg- ¥5-C · 0.92 0.92e 2-Butyl nitrate c'"ffl"/;1./0.3 0.905 0.905 

2-Pentyl nitrate\ 1 1.85 1.a5f 2.06 2.06 

3-Pentyl nitrate/ 1.12 1.12f 1.42 1.42 

2-Methyl-3-butyl nitrate >:' 1.72 1.72q 1.39 1.39 

2,2-Dimethyl-1-propyl nitratey 0.85 0.85q 0.752 0.752 

2 -Hexyl nitrate ) n206-3 ;-lt.-xy L AJ, n,"'~ic 3.17 3.17f 3.45 3.45 3 ·/1-<y 

2.1of 3-Hexyl nitrate J c&l-f!3.N'.:J3 2.70 2.58 2.58 

2-Methyl-2-pentyl nitrate , 1.72 1.72q 1. 68 1.68 

3-Methyl-2-pentyl nitrate/ 3.02 3.02q 2.63 2.63 

3-Heptyl nitrate~ 3.69 3.69q 3.97 3.97 

s:..octyl nitrate C,,;J<)- 3'}-0 3.88 3.aaf 5.37 5.37 CgH!j/'J() ~ 

B. CYCLIC NITRATES 

cyclohexyl nitrate 2/0'B .. ~u-') 3.30 3.30q 5.38 5.38 

c. ALKYL NITRILES 

Acetonitrile -:rs- oS-8 0.021 0.0214* 0.0202 0.0202 

Propionitrile Jor- ;~-o 0.19 0.194h 0.189 0.189 

-so-
•• 

~J 

. .. 

Table 18. continued 

a Experimental values from Atkinson (1989) and the literature. 

b Atkinson (1987, 1989) reported a value of 0.034x1o-12 and 

o.38x1o-12cm3molecule-1s-1 from Gaffney et al. (1986) and Kerr and Stocker 

(1986), respectively. Atkinson (1987) used the value of 0.034 x 10-12 since 

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. 

-81-
IV.C.S.b. Evaluation of the Estimated koH Data 

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 koH data. 

IV.C.6. Nitroalkanes 

IV.C.6.a. Evaluation of the Experimental k08 Data 

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 k08 • Atkinson (1989) evaluated the 

existing experimental k08 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 

(48) 

where C and D are constants and T is the absolute temperature in 

K and found that 

over the temperature range 299-671 K. At 298 K, equation 49 

gives 

-82-

(50) 

•• 
... 

.... 

Table 19. Comparison of the Estimated Values of koa at 298 K for 

Nitroalkanes and Alkyl Nitrites from the Atmospheric oxidation 

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

Experimental koa Data Reported in the Literature Versus the 

Experiment koa Data in AOP 

II 1012koH(cm3molecule-1s-1) 

Chemical Class/Chemi~ Experimental Estimated 

AOP (a) AOP(%Error)j 

A. NITROALKANES 

Nitromethane :;-s-sOJ-j- (0.016-0.16) 0.0149b 0.0259(+74) 

Ni troethane 1- ~- 21-'3 0.15 o.15d 0.194(+29) 

1-Nitropropane /oe- o3-"'2. 0.24 0.34d 0.632(+86) 

1-Nitrobutane (:,02 7- 05-i 1.45 1.45e 1. 79 (+23) 

1-Nitropentane &J8- o5-7 3.30 3.3od 3.18(-4) 

B. ALKYL NITRITES 

Methyl nitrite Wl.f- Cjl-9 (0.12-1.08)? (0.12-1. 09) f 0.288 (---) 

Ethyl nitrite /o9- 95-S'" 1. 75? 1.779 2.32(+31) 

1-Propyl nitrite 5'-/3 -61-9 2.38? 2.36h 6.12(+160) 

1-Butyl nitriteS'f-1-/(p-/ (2.31-5.2)? 5.o2h 8.29(+65) 

2-Butyl nitrite 9~¥-- 43-!o 5.93? 5.97i 6.17(+3) 

2-Methyl-1-propyl nitriteX 5.31? 5.35i 10.8(+101) 

2-Methyl-2-propyl nitrit~ 1.40? 1.41i 1.94(+38) 

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-

HC 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 
Table 19A. continued 

d Experimental value from Nielsen et al. (1988). Atkinson (1989) tentatively accepted this data since "The nitroalkanes are expected to photolyze (Taylor et al. (1990)] and it is not clear whether photolysis 

Nielsen 

occurred under the experimental conditions of the relative rate study of et al. (1988) or whether or not photolysis (if it occurred) was taken into account". More experimental k08 data are needed under controlled laboratory conditions to eliminate photolysis. e The average value from the data of Atkinson (1989) and Nielsen et al. 

Nielsen 

(1988). see footnote (d) above relative to the experimental value from et al. (1988). f Range in experimental koa data as obtained from Atkinson (1989) and the literature in the units 1o-12cm3molecule-1s-1: 0.12 relative to dimethyl ether and 0.21 relative ton-hexane (Tuazon et al. (1983)]; 1.00 [Baulch 

Goodman 

et al. (1985); 1.09 (Audley et al. (1982)]; and the data of campbell and 

with (1975) was omitted since there were fundamental problems associated 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 i et al. (1985) is obtained from Atkinson (1989). Experimental value from Audley et al. (1982). j 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 

remaining nitroalkanes, only for 1-nitropropane is there a 

discrepancy in the k08 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 koH 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 k08 data of Nielsen and 

stated that "The nitroalkanes are expected to photolyze (Taylor 

et al. (1980)] 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 Experimentalj(a) for 

nitroethane, 1-nitropropane, and 1-nitropentane from Nielsen are 

only tentatively preferred and, therefore, must be used with 

extreme caution. 

IV.C.6.b. Evaluation of the Estimated koH Data 

Leifer did not have available S/R relationships for the 

nitroalkanes from Atkinson; hence, no entries appear in Table 

-85-
19.A., column Estimated/He. Meylan (1990b) did have S/R 

relationships available for these compounds from Atkinson 

(unpublished results). For this class of compounds (RN02), 

Atkinson must have postulated that hydroxyl radicals can only 

react by abstractinq a hydroqen from the C-H qroups in R and the 

substituent factors were 

F(-N02) = 0.18 

F(-CH2N02) = 0.30 

(51) 

(52) 

In addition, Meylan (1990b) qave the substituents >CHN02 and 

>CN02 the same F values as for the substituent -cH2No2 listed in 

equation 52. Thus, the assumed values for these two substitutes 

(desiqnated **) are then 

F(>CHN02 ** ) = F(>CN02 ** ) = 0.30 (53) 

Usinq the above substituent factors, AOP estimated koH 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 koH data 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 ranqed from +53 to -4. Therefore, in order to 

develop better substituent factors for the nitroalkanes, more 

experimental koH data are needed for these five compounds and 

additional nitro compounds under carefully controlled laboratory 

-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 Experimentalf(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)cH20NO, AOP 

lists the name 3-methyl-1-propyl nitrite which is incorrect. The 

correct name is 2-methyl-1-propyl nitrite. 

-87-
IV.C.7.b. Evaluation of the Estimated koH Data 

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(-0-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 koHi and 

these values are listed in Table 19.8. 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-1-

propyl 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 

-as-
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.1.a. Evaluation of the Experimental koa Data 

Table 20 summarizes the pertinent experimental koa 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 koa data 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 koa to 4 significant figures while 

Experimentalf(a) reports koa to 3 significant figures. At best, 

the experimental k08 data is good to 3 significant figures. For 

example, for 2,3-dimethyl-2-butene, the experimental k08 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, 

Experimentalf(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 k08 at 298 K for Unsubstituted 

Alkenes from the Atmospheric Oxidation Computer Program (AOP) ~~ 

from a Hand Calculation (HC) and the Experimental kQH Data Reported 

in the Literature versus the Experimental koa Data 1n AOP 

Chemical Class/Chemica~ 1o12koH(cm3molecule-1s-1) 

Experimental Estimated 

AOP (a) AOP HC 

A. ACYCLIC ALKENES 

Ethene (Ethylene) 9t/- 8S- I 8.52 8.52* 8.5200q (r) 

Propene (Propylene) IIS-o 1-1 26.3 26.3* 26.4 26.4 

1-Butene /DI.P- 9 8"-~ 31.4 31.4* 27.3 27.3 

ili-2-Butene 59o-;8-l 56.4 56.4* 56.4 56.4 

trans-2-Butene &;J.4-t4-(» C!./11~ 64.0 64.0* 64.0 64.0 

2-Methylpropene ;;:)-;;-? c !.f!-1? 51.4 51.4* 51.7 51.7 

1-Pentene /o'1- r.,--:;-1 31.4 31.4* 28.6 28.6 

ill-2-Pentene (p.:J r- tJo-..3 65.4 65.7b 57.3 57.3 

trans-2-Pentene G:f/CP- o'l-~ 66.9 66.9c 64.9 64.9 

2-Methyl-2-butene 5/.3. 85' ... '-) 86.9 86.9* 87.3 87.3 

2-Methyl-1-butene 563 · '~"-- 2. 60.7 60.6d 52.6 52.6 

3-Methyl-1-butene 5&,3- 'Is-/ 31.8 31.8* 28.5 28.5 

1-Hexene 59~ -Jf;-~ 37.5 35.2e 30.0 30.0 

2-Methyl-1-pentene 1&?;- 29-1 62.6 62.6f 53.9 53.9 

2-Methyl-2-pentene {pJ~-.. 21-J./ 88.8 89.19 88.2 88.2 

trans-4-Methyl-2-pentenetr~~~-o 60.8 60.5f 66.0 66.0 

2,3-Dimethyl-2-butene5~3·7~J 110.0 110* 111 111 

3,3-Dimethyl-1-buteneJD8·37-~ 28.4 28.5h 26.9 26.9 

1-Heptene sr:jJ-.. 1~-1- 40.5 38.3i 31.4 31.4 

2,3-Dimethyl-2-penten,o5?~-31-S 108.0 103j 111 111 

trans-4,4-Dimethyl-2-pentene~ 54.5 54.5f 64.4 64.4 t;?O·o~-

1,4-Pentadiene ~1-93-~ 53.3 53.3C 53.4 53.4 

trans-1,4-Hexadiene~~)-45-o 90.3 90.6c 91.0 91.0 

1, 5-Hexadiene S9,;t- 'f~ -1- 62.1 62.0c 54.8 54.8 

-90-
Table 20. Continued 

/ 

l012koH{cm3molecule-ls-1) 

Chemical Clas~ical Experimental Estimated 

2-Methyl-1, 4-pentadiene-1&3·30-'t 

2-Methyl-1 5-hexadiene c. ?HI~ .:2'1 Lf1: 1:. !.. 3 i- -'(? 5tif·U 

2,5-Dimethyl-1,5-hexadiene (;~1- 58-1 

B. CYCLIC ALKENES 

cyclopentene lt/-:J-;2 ~-O 

Cyclohexene 110- 83-8 

1, 4-Cyclohexadiene '2CJ1'}7- 09-q 

Cycloheptene tl:l~-q~- z. 

1-Methylcyclohexene 5~/-l.ft:7-l 

Bicyclo [2. 2 .1] -2-heptene'io/5-u-~ C1Hr30 

Bicyclo[2.2.1]-2,5-heptadiene /;lJ-"'fa-0 Bicyclo[2.2.2]-2-octene LL 

~31· "' ~ a-Pinene $0- SIC-~ 

P-Pinene 1;;; =! -91-3 

g-Limonene S7&9-c:;=f-$" tf 

43-carene 13J.jbr/l - 18:~_9 

-y-Terpinene C)~- ?SS-'f 

AOP 

78.8 

96.1 

120.0 

67.3 

67.7 

99.4 

74.4 

94.4 

49.3 

120.0 

40.8 

53.7 

78.9 

171.0 

{p) 

177.0 

{a_) AOP 

78.8c 78.7 

96.lc 80.0 

120c 105 

65.5k 58.9 

67.7* 61.1 

99.51 114 

74.4m 62.4 

94.4n 92.0 

49.3m 62.7 

120m 116 

40.8m 67.8 

53.7* 89.5 

78.9* 54.2 

160n 145 

87.8° 87.6 

177° 178 

a Experimental values from Atkinson {1989) and the literature. 

HC 

78.7 

80.0 

105 

58.9 

61.1 

114 

62.5 

92.0 

62.7 

116 

67.8 

89.5 

54.1 

145 

87.6 

178 

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 and £1§-2-pentene as reference compounds. 

-91-
h Experimental value from Wu et al. (1976) and Atkinson (1989). 

i Average value of the experimental data of Darnall et al. (1976) and 

Atkinson and Aschmann (1984). 

j 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. 

1 Average 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). 0 Experimental value from Atkinson, Aschmann, Pitts (1986). 

P No experimental value is qiven in the AOP database. An experimental value 

of 87.8x1o-12cm3molecule-ls-1 is 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-

..... 

... 
(1990b)]. The value of 87.8 should be listed in the AOP 

database. 

IV.D.1.b. Evaluation of the Estimated koH Data 

Comparison of the estimated koH 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; koH cannot be 

estimated by the S/R relationships of Atkinson. Furthermore, AOP 

lists the estimated value to five significant figures which 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 • (CH2•CHR)[C(R)] • 26.3(1.00) 

(55) 

kadd,nar • 26.3 

For 2-methyl-2-pentene, 

kadd,nar 

-93-
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) = 0). 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 k08 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 

k08 values 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 koH at 298 K for Substituted 

Alkenes 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 koH Data ~n AOP 

Chemical Class/Che~ 

A. Haloalkenes 

Vinyl fluoride ?5"02-!.)-

Vinyl chloride =!S-Ol-'-/ 

Vinyl bromide593- ~O- 2... 

1, 1-Difluoroethene :::rs-3<:?"'1 

w-1, 2-Dichloroethene I&/!;D-7~-9 

trans-1, 2-Dichloroethene/(,~~~f-(.) 

Trichloroethane -=r 9-o/-cD 

(Trichloroethylene) 

Tetrachloroethane I J.. 1'- Je> -y (Tetrachloroethylene) 

3-Chloro-1-propene Jo'T- OS"' J 

(3-Chloropropylene) 

cis-1,3-Dichloro-1-propene /O~t-ol-5 trans-1,3-Dichloro-1-propene lo tJ "1-oZ- 4:J 2-(Chloromethyl)-3-chloro1-propene 18 f I-57 -·i 

C 'I /-f W U 1

c:J. 

B. a,B-UNSATURATED CARBONYLS 

Acrolein (2-Propenal)/O=t-02-€ 

trans-crotonaldehyde(trans2-Butenal) j;;:;-'13- 9 

Methacrolein(2-Methyl-2-

propenal) -=f-.!5-BS-3 

Experimental 

AOP (a) 

5.56 5.56b 

6.60 6.6ob 

6.81 6.81b 

2.1 2.1c 

2.38 2.38d 

1.80 1.8od 

2.36 2.36* 

0.167 0.167* 

17.0 17* 

8.41 8.41d 

14.3 14.3d 

(e) 33.5d 

19.9 19.9* 

(e) 36* 

33.5 33.5* 

-95-

Estimated 

AOP HC 

10.5 10.5 

5.26 5.26 

6.84 6.84 

8.22 8.22 

2.24 2.24 

2.55 2.55 

0.695 0.695 

0.176 0.176 

20.3 20.3 

8.85 8.85 

10.0 10.0 

30.3 

22.9 22.9 

32.8 32.8 

29.6 29.6 
Table 21. Continued 

1o12k (cm3molecule-1s-1) 

Chemical Class/Chemical Experimental Estimated 

I 

Methyl vinyl ketone ':J ~-9'1-1 

Ketene If~ 3- 51-J./ 

Methyl ketene>( 

Ethyl ketene:X 

Dimethyl ketene Y 

ill-3-Hexene-2, 5-dione 17"";1

,'/- 21-S' 

trans-3-Hexene-2,5-dione . -.S..)o~ (.,c~;;-c; 

C. NITRILOALKENES 

Acrylonitrile (Cyanoethene) 

1or-- 13-t 

D. ALKOXY ALKENES 

Methyl vinyl ether 

lor-~s-sAOP 

18.8 

(e) 

(e) 

(e) 

(e) 

63.1 

53.1 

4.0 

33.5 

(a) AOP 

18.8* 24.0 

173f 51.4 

70g 87.0 

118f 87.9 

107f 110 

63.1h 46.7 

53.1h 53.0 

3.95 

33.5b 35.1 

a Experimental values from Atkinson (1989) and the literature. 

b Experimental value from Perry, Atkinson, Pitts (1977a). 

HC 

24.0 

51.4 

87.0 

87.9 

110 

46.7 

53.0 

3.95 

35.1 

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). i 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-1-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 koa Data 

A comparison of the estimated values of koa 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 thr~e significant figures in the summary table 

are applicable in the same manner as described in previous 

sections. 

IV.D.3. Conjugated Dienes 

IV.O.J.a Evaluation of the Experimental koa Data 

Table 22 compares the pertinent experimental koa data 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 koa 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. 

Acyclic 

Comparison of the Estimated Values of koH at 298 K for Conjugated '• and cyclic Dialkenes from the Atmospheric Oxidation computer Program (AOP) and from a Hand Calculation (HC) and the Experimental koa Data Reported in the Literature Versus the Experimental koa Data in AOP 

1o12koH(cm3molecule-1s-1) 

Chemical Class/Chemical Experimental Estimated 

AOP (a) AOP 

A. ACYCL~IALKENES 

1, 3-Butadiene IOC,-9'1· 0 66.6 66.6* 66.6000g 

~-1,3-Pentadiene 1~1~-11-0 101.0 101b 105 

2 -Me thy 1-1, 3-butadiene 7~:- 1-9--S' 101.0 101* 105 

trans-1,4-Hexadiene)( 112.0 112b 106 

3-Methyl-1, 3-pentadiene tp4CJ-:tl/-u 136.0 136b 135 

4-Methyl-1, 3-pentadieneql(o-_50-7- 131.0 131b 135 

2,3-Dimethyl-1,3-butadiene _ 122.0 122b 135 513-81~ 

210b 2,5-Dimethyl-2,4-hexadiene 3 C-8,/-f ~ 210.0 231 !'-/ 70'/- I -

3-l~ethylene-7-methyl-1, 6-

octadiene (Myrcene) /23 -35"-3 215.0 215c 194 

3,7-Dimethyl-1,3,6-octatriene 252.0 252c 223 

/3877- 91-3 

B. GYCLIC OIAIJ(ENES 

1, 3-Cyclohexadiene 59~ -s-:;--'-1 164.0 164d 137 

1, 3-Cycloheptadiene </~~-/;! -D 139.0 139e 139 

a-Phellandrene 9~-8'3- 2. 313.0 313f 187 

a-Terpinene C)CJ-&b-S" 363.0 363f 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). 9 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-

HC 

(h) 

105 

105 

106 

135 

135 

135 

231 

194 

223 

137 

139 

187 

235 
IV.D.3.b. Evaluation of the Estimated koa 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 koa Data 

Table 23 summarizes the pertinent experimental koa 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 koa 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 koa Data 

Except for ethyne, butadiyne, and propadiene, the estimated 

values of koa at 298 K in columns 4 and 5 are identical. For 

these three compounds, no estimated values appear under the 

-99-
Table 23. Comparison of the Estimated Values of koH 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 

1o12koH(cm3molecule-1s-1) 

Chemical ClassjChem~~ Experimental Estimated 

AOP (a) AOP 

A. ALKYNES 

Ethyne (Acetylene) 'JL/-'F{'b-<- 0.815 0.815 0.8150b 

Propyne 7 '-/ ~-1- 5.90 5.9* 6.54 

1-Butyne jo=f-OO-~ 8.00 8.0* 7.42 

2-Butyne 503- 17- 3 27.4 27.4* 29.3 

1-Pentyne 0 Jl-19-0 11.2 11.2d 8.75 

1-Hexyne &q3-CJ2--.:t- 11.9 12.6d 10.1 

Butadiyne (Diacetylene) 18.9 18.9* 14.08 'l&o- J;J -?? 

B. 1,2 DIENES (ALLENES) 

Propadiene "/(o3 -LJ9 -o 9.82 9.84* 9.820b 

1 I 2-Butadiene sqo- /t:7j- 2_ 26.1 26.1e 31.1 

1, 2-Pentadiene 59 J _ t!JS-j 35.5 35.5e 32.0 

3-Methyl-1,2-butadiene 56.9 56.9e 57.3 

~~-~5-tf 

a 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). 

HC 

(c) 

6.54 

7.42 

29.3 

8.25 

10.1 

(c) 

(c) 

31.1 

32.0 

57.3 

* Recommended by Atkinson (1989) with the rationale for the recommendation, and the uncertainty for the recommendation. 

-100-
.. 

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 significant figures. 

IV.E. Reaction of Hydroxyl Radicals with Organic Compounds 

Containing Sulfur, Nitrogen, and Phosphorous Functional 

Groups 

IV.E.l. Reaction with Thiols, Sulfides, and Disulfides 

IV.E.l.a. Evaluation of the Experimental koH 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 koH 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 Experimentalf{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 koH 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-
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 k ~oH Data in AOP 

lo12koH(cm3molecule-ls-1) 

Chemical Class/Chemica~ Experimental Estimated 

AOP (a) AOP 

A. THIOLS 

Methanethiol -:;t/-93- I 32.9 32.9* 32.3 

Ethanethiol 15' -C"B- I 46.8 46.8* 38.7 

1-Propanethiol /01·03~ 48.3 48.3* 42.0 

2-Propanethiol =rs- 3 3-z 42.0 42.0* 47.8 

1-Butanethiol/o<f-r<J--5" 51.0 51* 43.4 

2-Methyl-1-propanethiol 45.0 45* 43.5 513- tf~-0 

2-Butanethiol573 -S3-I 40.0 40* 53.7 

2-Methyl-2-propanethiol 33.1 33.1* 31.6 ;.s-:~-1 2-Methyl-1-buta et 101 54.0 54.3b 44.9 18¥&-Jtr-~ B.l. ACYCLIC SULFIDESe 

Dimethyl sulfide15-J2-3 4.56 4.56* 4.59 

Methyl ethyl sulfide 8.5 8.soc 11.0 

Diethyl sulfide~oo-z4-~ 15.0 15* 17.5 

Di-n-Propyl Sulfidet//-'!1--f 20.0 2o.od 24.0 (Jol-{/~6 B.2. CYCLIC SULFIDE e 

Tetrahydrothiophene 19.7 19.7* 19.8 /to-ol-o 

c. DISULFIDES 

Dimethyl disulfide (f) 211* 203 

=;s- JB-3 

a Experimental values from Atkinson (1989) and the literature. b Experimental value from Barnes et al. (1986). 

HC 

32.3 

38.7 

42.0 

47.8 

43.4 

43.5 

53.7 

31.6 

44.9 

2.59 

9.02 

15.5 

22.0 

17.8 

203 

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, koH was measured in the absence of oxygen. 

-102-

.... 
Table 24. continued 

f No experimental value is given in the AOP database. An experimental value of 211x1o-12cm3molecule-1s-1 is given in the document "Estimation 

Accuracy of AOP versus PCFAP" [Meylan (1990b)]. 

•·Recommended value by Atkinson (1989) with the rationale for the 

recommendation, and the uncertainty for the recommendation. 

-103-
Finally, for 2-methyl-1-butanethiol, the correct experimental 

value of koa 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.1.b. Evaluation of the Estimated koa Data 

A comparison of the estimated koa data from AOP and HC 

indicates that they are the same except for the alkyl sulfides 

(acyclic and cyclic). For all these sulfides, koa is larger 

from AOP than from HC. The reason for the differences will be 

described in the following paragraphs. 

In estimating k0a, there are two reaction pathways for the 

reaction of OH radicals with alkyl (acyclic and cyclic) sulfides: 

(i) H-atom abstraction from the C-H groups in the alkyl groups; 

and (2) OH radical interaction with the sulfide group to form the 

adduct (>S····OHJ which then decomposes rapidly in the presence 

of oxygen to form the products. The total rate of reaction is 

then given by the eq~ation 

koa = k(l) + 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) 

and only C-H abstraction from the alkyl groups takes place. 

In estimating k0 H, AOP uses equation 57 while HC uses 

equation 58 and this is the reason why koa (AOP) > koH(HC). 

Since the experimental values listed in the column 

-104-

(58) 
. 

•• 

Experimentalf(a) were obtained in rate measurements without 

oxygen, koa must be evaluated using equation 58. Therefore, AOP 

must qualify the experimental k08 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-) = o in the 

absence of oxygen. 

IV.E.2. Reaction with Sulfoxide& and Sulfates 

IV.E.2.a. Evaluation of the Experimental koa Data 

Table 25 summa~izes the pertinent experimental koH data 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 

sulfoxide& 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, 

-lOS-
Table 25. Comparison of Estimated Values of koij at 298 K for Alkyl Sulfoxides and sulfates from the Atmospheric ox~dation computer Program (AOP) and from a Hand Calculation (HC) and the Experimental koa Data 

Reported in the Literature Versus the Experimental k08 Data in AOP 

Chemical Class/Chemical~ 1o12koH(cm3molecule-1s-1) 

Experimental Estimated 

AOP (a) AOP(\Error)f 

A. SULFOXIOES 

Dimethyl sulfoxideb~-hg-s- 62.0 62b 28.5(-54) 

B. SULFATES 

Dimethyl sulfate 11-1-~ -1 <0.5 <0.5c 1.76{>+250) 

Diethyl sulfate &tf-- lt;)f-S' 1.8 1.8d 11.5 (+540) 

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 Experimentalf(a). 

-106-

HC 

(e) 

(e) 

(e) 
koa = k(1) (59) 

F[S{+4) ** ] = 99.000 (Table 2) (60) 

Using equations 59, 60, and 11, AOP estimated that koa 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 

R-S(•O) + ·OH ---

0 

II r-s· · · ·OH 1 

Rapid 

02 

Products { 61) 

and this reaction pathway should be considered in the S/R 

relationships. Therefore, considerably more experimental koa 

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-o-) were valid. 

Using equations 62 and 11 along with the appropriate substituent 

-107-
Table 27. continued 

Chemical Class/Ch~ 10 12 kn~(cm3molecule-1s-1) 

Experimental Estimated 

AOP (a) AOP HC 

B. DIALKYL CHLOROPHOSPHOROTHIOATES 

o,o-oimethyl chlorophosphorothioate 

(CH3o) 2P(S)Cl ;JSJLj-03-0 

59.0 59.oc 60.8 60.8 

c. ALKYL PHOSPHOROAMIDATES 

AND ALKYL PHOSPHOROTHIOAMIDATES 

O,O-Dimethyl 

phosphoroamidothioate 244.0 244e 80.8 80.8 

(CH30)2P(S)NH2 

I 1/J.:..J;- 1/7-(' 

( "lit,<jAJ (J 2 P5 

O,O,N-Trimethyl y phosphoroamidothioate 232.0 232e 122 122 

(CH30)2P(S)NHCH3 

o,o,N,N-Tetramethyl ' ' 

phosphoroamidothioate !\ 46.8 46.8e 124 124 

(CH30)2P(S)N(CH3)2 

o,o,N,N-Tetramethyl 

phosphoroamidate 

(CH30)2P(O)N(CH3)2 31.9 31.9e 68.6 68.6 

a Experimental data from the literature. b Experimental data from Atkinson (1989) and Tuazon et al. (1986). c Experimental data from Atkinson (1989) and Atkinson et al. (1988). d Experimental data from Atkinson (1989) and Goodman et al. (1988). 

e Experimental data from Atkinson (1989) and Goodman et al. ( 1988a) . 

-112-
trimethyl phosphate, 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(=O)] = 0.000 (63) 

and for (CH3o) 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) 

(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.1.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-
• 

,} 

Table 28. Comparison of Estimated Values of koH at 298 K for Aromatic 

Compounds from the Atmospheric Oxidation Program (AOP) and from 

Hand Calculation (HC) and the Experimental kQH Data Reported in 

Literature Versus the Experimental koH Data ~n AOP 

Chemical Class/Chemica~ 

A. UNSUBSTITUTED AROMATIC 

COMPOUNDS 

Benzene =! 1-'-13 -1 

Biphenyl q;; ~s()-L/ 

B. ALKYLBENZENES 

Methylbenzene (Toluene) ;o ~- s-a-3 

Ethylbenzene /oO -¥ 1-J.f 

n-Propylbenzene jo?rft:JS- J 

i-Propylbenzene q&'~z-g 

t-Butylbenzene C) 'II- ol.-(p 

Q-Xylene t:}~~4f1-lo 

m-Xylene ;o~-3~- ~ 

R-Xylene /()~ -~~- 3 

Q-Ethyltoluene foll-/'-1- 3 

m-Ethyltoluene (p~o- !+'f 

R-Ethyltoluene d;;)J-Cjfo-g 

1,2,3-Trimethylbenzene ~(Q- =t-3-8 

1,2,4-Trimethylbenzene 9S- ~3-<D 

1,3,5-Trimethylbenzene ;o??- h7-'8 

a 

the 

1012koH(cm3molecule-1s-1) 

Experimental Estimated 

AOP (a) AOP HC 

1.23 1.23* 2.04 2.04 

7.2 7.2* 7.12 7.12 

5.96 5.96* 5.51 5.51 

7.1 7.1* 6.13 6.13 

6.0 6.0* 7.46 7.46 

6.5 6.5* 7.08 7.08 

4.60 4.6ob 5.08 5.08 

13.7 13.7* 6.88 6.88 

23.6 23.6* 14.4 14.4 

14.3 14.3* 6.88 6.88 

12.3 12.3* 7.72 7.72 

19.2 19.2* 14.6 14.6 

12.1 12.1* 7.72 7.72 

32.7 32.7* 17.8 17.8 

32.5 32.5* 17.8 17.8 

57.5 57.5* 37.5 37.5 

-114-

.. 
c. • Table 28. continued 

Chemical Class/Chemical Experimental 

tf,--+---- AOP (a) 

C. ALKENYLBENZENES 

Ja:J-'-/~ -6-

Phenylethene (Styrene) 

2-Phenyl-1-propene a ..o (a-Methylstyrenef/t-~3 ' 

1-Phenyl-1-propene ~ 3 r-so-3 (~-Methylstyrene) 

1-Phenyl-2-methyl- cH,Nifj_ 

1-propene {16 -11-~ 

(~-Dimethylstyrene~ 

D. HALO BENZENES 

Fluorobenzene '-/to~--~-~ 

Chlorobenzene /o8-c;Jo- -=1-

Bromobenzene /08-?S(Q-/ 

Iodobenzene SC}J-s-o-4-

.Q-Dichlorobenzene 95"SZJ -J 

m-Dichlorobenzene 9-fl- 13-J 

R-Dichlorobenzene /o~-'16-7 

1,2,4-Trichlorobenzene /.:J0-87.-- 1 

Hexafluorobenzene 392.-~# 3 n-Propylpentafluorobenzene '/ 

C})HtFS 

E. HALOALKYLBENZENES 

Benzotrifluoride 98"-of-t4-Chloro~enzotrifluoride 

~~-G1 C~HJ7CRF3 Benzyl c ,lorJ.de 

'38'-88-'f 

58.0 

33.0 

0.69 

0.77 

0.77 

1.1 

0.42 

0.72 

0.32 

0.532 

0.172 

3.06 

0.46 

0.24 

2.9 

-115-

58* 

59c 

0.69* 

0.77* 

0.77* 

1.1* 

0.42e 

0.72e 

0.32e 

0.532f 

0.172* 

0.46h 

0.24h 

2.9* 

Estimated 

AOP 

28.2 

53.5 

65.8 

89.1 

2.56 

1.43 

1.28 

1. 34 

0.414 

1.01 

0.414 

0.291 

0.151 

2.89 

0.406 

0.285 

2.42 

HC 

28.2 

53.5 

65.7 

89.1 

2.56 

1.42 

1.28 

1.34 

0.414 

1. 01 

0.414 

0.291 

0.151 

2.90 

0.406 

0.285 

2.43 
Table 28. continued 

1012koH(cm3molecule-1s-1) 

Chemical Class/Chemic~ Experimental Estimated 

AOP (a) AOP HC 

F. MONOCHLOROBIPHENYLS 

2-Chlorobiphenyl2c5l- W--=1 2.8 2.82i 2.95 2.95 

3-Chlorobiphenyl ZC::OI- l.ol-8' 5.3 5.28i 4.42 4.42 

4-Chlorobiphenyl ldi 1-~2- ~ 3.9 3.86i 2.95 2.95 

G. HYDROXYBENZENES 

Phenol I08-~5' -'2.... 26.3 26.3* 35.7 35.6 

.Q-Cresol ~5-"f~-1- 42.0 42* 43.9 43.9 

m-cresolJog-39-~ 64.0 64* 93.9 93.9 

R-Cresol 10~-~-~- 47.0 47* 43.9 43.9 

2, 3-Dimethylphenol52.lo-?5·0 80.2 80.2j 115 115 

2, 4-DimethylphenolloS"-~~-'? 71.5 71.5j 54.1 54.1 

2, 5-DimethylphenolC]S-~1-·~ 80.0 8o.oj 115 115 

2,6-Dimethylphenol51~-2w' 65.9 65.9j 54.1 54.1 

3, 4-Dimethylphenol<::}":)-(;,5"-~ 81.4 81.4j 115 115 

3,5-Dimethylphenoll~-~~9 113.0 113j 200.3 200 

2, 3-Dichlorophenol).(l.o-ZJ.I-'} 1.66 1.66k 7.27 7.27 

2, 4-DichlorophenoliZo-83- ..,_ 1.06 1.06k 3.02 3.02 

H. NITROBENZENES 

Nitrobenzene "8-~S- 3 0.14 0.1491 0.251 0.251 

.Q-Nitrophenol 8~- -=15"-:J 0.90 0.90 4.42 4.42 

.Q-Nitrotoluene ~2-12.-L. 0.70 0.70 0.805 0.805 

m-Nitrotoluene 99-of!-1 0.95 0.95 0.605 0.605 

-116-
•• Table 28. continued 

lol2koH(cm3molecule-ls-l) 

Chemical Class/Chemic~ Experimental Estimated 

AOP (a) AOP HC 

I. AMINO BENZENES 

Aniline ~;2--53- :3 111.0 111* 136 136 

N, N-Dimethylaniline IZI-U.er~ 148.0 148m 263 200 

Q-ChloroanilinejO~-~~-~ 83.0 83.on 53.6 53.6 

2,4-Toluenediamine qs--~o-1-

192.0 192° 240 200 

J. ADDITIONAL SUBSTITUTED 

BENZENES 

Methoxybenzene laD-(:,{;;,-.3 17.3 17.3* 23.8 23.8 

Benzonitrile joo-L/-=}-0 0.33 0.33 0.356 0.356 

Benzaldehyde } a:? -s-()-r 12.9 12.9* 17.1 17.1 

Acetophenone q~ -&<o-2.. 2.74 2.74P 1. 61 1. 61 

Thiophenol /o8- 98-S"" 

(Mercaptobenzene) 11.2 11.2q 13.3r 13.3r 

Benzyl alcohol joO-SJ-~ 22.9 22.9 7.99 7.99 

Tetra lin ( 1, 2, 3, 4- /1'1-~- 2.. 

Tetrahydronaphthalene) 34.3 34.38 11.1 11.2 

Indan (2,3-Dihydro- 9. 2t lH-indene) 49~-1 1-7- 9.2 9.71 9.09 

Fluorene (9H-Fluorene) 13.0 13.ou 9.42 9.37 

gt; -73-1' 1,4-Benzodiox1n 25.2 25.2 33.0 33.0 

2,3-Dihydrobenzofura~ 36.6 36.6 38.0 36.3 

'-1~4:>-rl. ~- 1,4-Naphthoqu no e 3.1 3.1 2.75 2.75 

}3o- /S-f 

-117-
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). 

i Experimental data from Atkinson and Aschmann (1985). 

j 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). 0 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)=O [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 Klopffer 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-

•• 
•• 

Atkinson (1989) recommends a value of 111*. 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-benzodioxin, 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.1.b. Evaluation of the Estimated Data 

A comparison of the estimated values of koH by 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 1o-12cm3molecule-1s-1 whereas HC lists a maximum value of 

koH [equation 9] as 200 x 1o-12cm3molecule-1s-1. Since the 

maximum allowed collision rate is 200 x 1o-12cm3molecules-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 ai (-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(1c) 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 koH for these 

compounds are erroneous. 

Finally, for t~e compounds P-methylstyrene, chlorobenzene, 

n-propylpentafluorobenzene, benzylchloride, and phenol, the small 

differences between the estimated k08 from 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 k08 data 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-
J • 

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 koa Data Reported in the Literature 

Versus the Experimental koH Data in AOP 

1o12koH(cm3molecule-1s-1) 

Chemical / Experimental Estimated 

AOP (a) AOP 

Furan I lo-oo-9 40.5 40.5* 4o.5b 

3-Methylfuran 930- 2 -=f- ~ 93.5 93.5d 106.7{+14)h 

Thiophene /lo -o2 -1 9.53 9.53* 9.53b 

Pyrrole /oCJ-'>1-1- 110.0 110* b 110.0 

Imidazole 28~- 32-~ 36.0 35.9e 36.ob 

oxazole z..a~-i/2.-CP 9.1 9.1e 9.1ob 

Thiazole 288-4 7- J 1.40 1.41e 1. 40b 

Pyridine J/o-"8v 1 0.37 0.37f o.37ob 

1,3,5-Triazine 0.15 0.145g 0.150b 

'290- 8:t-~ 

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 

HC 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

(c) 

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 koH in column Experimentalf(a). 

-121-
thiazole, the correct values of koH 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 

rinq; and (2) the second term is identical to the one used by 

Atkinson for substituents on the aromatic rinq [i.e., -1.35 Min 

<l:aj) in equation 21]. The values of Ai are qiven in Table J 

10 for a number of parent heterocyclic aromatic rinqs. 

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 qives a percent error of +14 which is excellent. 

However, more experimental koH 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-
. ' 

IV.F.3. Fused Rinq Polyaromatic Compounds 

IV.F.3.a. Evaluation of the Experimental koa Data 

Table 30 summarizes the pertinent experimental koa data for 

the reaction of hydroxyl radicals with fused rinq polyaromatic 

compounds [i.e., fused rinq 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 koa data 

for fused rinq 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 koa Data 

A comparison of the estimated values of koa 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 koa for the parent PAH 

(which is Bi in equation 29) while Atkinson uses the ionization 

potential of the parent PAH. For naphthalene, both methods qive 

essentially the same results; however, for anthracene and 

-123-
Table 30. Comparison of the Estimated Values of koH 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 

1o12koH(cm3molecule-1s-1) 

Chemical Experimental Estimated 

AOP (a) AOP 

Naphthalene 91-.;l o-3 21.6 21.6* 21.6b 

1-Methylnaphthalene 9o-rz-o 53.0 53.0C 56.9 

2-Methylnaphthalene91-S1-~ 52.3 52.3d 56.9 

2,3-Dimethylnaphthalene 76.8 76.8d 70.0 

.;::'- Ll~ -e 1-Nitronapht lene ~ 5.4 5.4e 2.66 at.a-St"' 2-Nitronaphthalene 5.6e 89 _ 5.6 2.66 58h -,!) 1,4-Dichloronapht alene 5.8 5.8f 4.38 182.5-aJ-(o Anthracen~~ r 110.0 112g 11o.ob 0 .. /2.-

Phenanthrene 31.0 31* 31.ob 

85"-o/- '8' 

a Experimental data from Atkinson (1989) and the literature. 

b Experimental data for this compound. 

HC 

21.4 

56.3 

56.3 

69.5 

2.63 

2.63 

4.37 

91.2 

22.9 

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 Kl6pffer 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-

• .. f t 
.. 

l • 

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 ~f 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 [tc 1/ 2)El 

for the reaction of hydroxyl radicals with organic chemicals in 

the troposphere by assuming that the average OH radical 

concentration was 5 x 105 radicals cm-3 and 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 

106 radicals 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-
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, 

I I kox = koH + ko3 (66) 

I I where koH and k 03 are 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 106 radicals cm-3 and a 

12-hour daylight day and (03) = 7 x loll molecules cm-3; and the 

overall oxidative half-life is given by the equation 

[ tc 1t 2>] ox = o. 693/kox (67) 

Thus, AOP should add 

SUMMARY: OXIDATION 

kox = (68) 

t(l/2)ox = (69) 

-126-

. 

v 
v. References 

Anderson, L.G.; Stephens, R.D. (1988). 

Int. J. Chem. Kinet. 1Q, 103-110. 

Kinetics of the Reaction of Hydroxyl Radicals with 

2-(Dimethylamino)ethanol from 234-364 K. 

Anastasi, C.; Smith, I.W.M.; Parkes, D.A. (1987). 

J. Chem. Soc. Faraday Trans. 1, li, 1693. 

Arey, J.; Atkinson, R.; Zielinska, B.; McElroy, P.A. (1989). 

Environ. Sci. Techno!. ~, 321-327. Diurnal Concentrations of 

Volatile Polycyclic Aromatic Hydrocarbons and Nitroarenes During 

a Photochemical Air Pollution Episode in Glendora, California. 

Arrhenius, s. (1887). 

z. Physik Chem. ~, 110. 

Atkinson, R. (1986)~ 

Chem. Rev. 12, 69-201. 

Kinetics and Mechanisms of the Gas Phase Reactions of the 

Hydroxyl Radical with Organic Compounds under Atmospheric 

Conditions. 

Atkinson, R. (1986a). 

Int. J. Chem. Kinet. ~, 555-568. 

Estimation of OH Radical Rate Constants for H-Atom Abstraction 

from c-H and o-H Bonds over the Temperature Range 250-1,000 K. 

Atkinson, R. (1987). 

Int. J. Chem. Kinet. li, 799-828. 

A Structure-Activity Relationship for the Estimation of Rate 

Constants for the Gas-Phase Reactions of OH Radicals with Organic 

Compounds. 

Atkinson, R. (1987a). 

Environ. Sci. Technol. 11, 305-307. 

Estimation of OH Radical Reaction Rate Constants and Atmospheric 

Lifetimes for Polychlorobiphenyls, Dibenzo-R-dioxins, and 

Dibenzofurans. 

Atkinson, R. (1988). 

Env. Toxic. and Chem. 2, 435-442. 

Estimation of Gas-Phase Hydroxyl Radical Rate Constants for 

Organic Chemicals. 

-127-
Atkinson, R. (1987b, 1988a). In OECD (Organization for Economic Cooperation and Development) Test Guideline on Photochemical Oxidative Degradation in the Atmosphere. 

1. Draft Final Report Dated January, 1987b. Revision 2, p. 49- 113. 

2. Draft Final Report Dated August, 1988a. Revision 3, p. 19-42 and Annex III (Forty-eight examples are given for the estimation of the rate constants koH>· Umweltbundesamt Berlin, Bundesrepublik Deutschland. Estimation of OH Rate Constants. 

Atkinson, R. (1989). Monograph No. 1. Kinetics and Mechanisms of the Gas-Phase Reactions of the Hydroxyl Radical with Organic Compounds. American Chemical Society, Wash., D.C. and American Inst. of Physics, New York, N.Y. 

Atkinson, R. (1989a). Unpublished Results. 

Updating of the Structure/Reactivity Relationships for the Reaction of OH Radicals with Organic Chemicals in the Gas-Phase. 

Atkinson, R.; Aschmann, S.M. (1984). Int. J. Chem. Kinet. 1!, 1175-1186. 

Rate Constant for the Reaction of OH Radicals with a Series of Alkenes and Dialkenes at 295 ± 1 K. 

Atkinson, R.; Aschmann, S.M. (1985). Environ. Sci. and Techno!. ~, 462-464. 

Rate Constants for the Gas-Phase Reaction of Hydroxyl Radicals with Biphenyl and the Monochlorobiphenyls at 295 ± 1 K. 

Atkinson, R.; Aschmann, S.M. (1986). Int. J. Chem. Kinet. 11, 569-573. 

Kinetics of the Reaction of Naphthalene, 2-Methylnaphthalene, and 2,3-Dimethylnaphthalene with OH Radicals and with o3 at 295 ± 1 K. 

Atkinson, R.; Aschmann, S.M. (1987). Atmos. Environ. 11, 2323-2326. 

Kinetics of the Gas-Phase Reactions of Alkylnaphthalenes with o3, N2o5 , and OH Radicals at 298 ± 2 K. 

Atkinson, R.; Aschmann, S.M. (1988). Int. J. Chem. Kinet. 1Q, 339-342. 

Rate constants for the Reaction of OH Radicals with Isopropylcyclopropane at 298 ± 2 K: Effects of Ring Strain on Substituted Cycloalkanes. 

-128-

" 

""" 

i.. 

T 

., ~ 
Atkinson, R.; Aschmann, S.M. (1988a). 

Int. J. Chem. Kinet. AQ, 513-539. 

Kinetics of the Reactions of Acenaphthalene and Structure-Related 

Aromatic Compounds with OH and N03 radicals, N205, and 03 at 296 

± 2 K. 

Atkinson, R.; Aschmann, S.M. (1989). 

Int. J. Chem. Kinet. ~, 355-365. 

Rate constants for the Gas-Phase Reactions of the OH Radical with 

a Series of Aromatic Hydrocarbons at 296 ± 2 K. 

Atkinson, R.; Aschmann, S.M. (1989a). 

Int. J. Chem. Kinet. ~, 1123-1129. 

Rate constants for the Reaction of the OH Radical with the Propyl 

and Butyl Nitrates and 1-Nitrobutane at 298 ± 2 K. 

Atkinson, R.; Carter, W.P.L. (1984). 

Chem. Rev. ii, 437-470 

Kinetics and Mechanisms of the Gas-Phase Reactors of ozone with 

Organic Compounds Under Atmospheric Conditions. 

Atkinson, R.; Aschmann, S.M.; Carter, W.P.L. (1983). 

Int. J. Chem. Kinet. 12, 1161-1177. 

Effects of Ring Strain on Gas-Phase Rate Constants; 2. OH Radical 

Reactions with cycloalkenes. 

Atkinson, R.; Aschmann, S.M.; carter, W.P.L. (1983a). 

Int. J. Chem. Kinet. 12, 37-50. 

Rate constants for the Gas-Phase Reactions of OH Radicals with a 

Series of Bi- and Tricycloalkanes at 299 ± 2 K. Effects of Ring 

strain. 

Atkinson, R.; Aschmann, S.M.; carter, W.P.L. (1984a) 

Int. J. Chem. Kin • .1§., 967-976. 

Kinetics of the Reactions of o3 and OH Radicals with a series of 

Dialkenes at 294 ± 2 K. 

Atkinson, R.; Aschmann, S.M.; Pitts, Jr., J.N. (1986). 

Int. J. Chem. Kinet. 11, 287-299. 

Rate Constants for the Gas-Phase Reactions of the OH Radicals 

with a Series of Monoterpenes at 294 ± 1 K. 

Atkinson, R.; Perry, R.A.; Pitts, Jr., J.N. (1977). 

J. Chem. Phys. ii, 1578-1581. 

Rate Constants for the Reaction of the OH Radical with CH3SH, 

CH3NH2 over the Temperature Range 299-426 K. 

-129-
Atkinson, R.; Perry, R.A.; Pitts, Jr., J.N. (1978). 

J. Chem. Phys., 1850-1853. 

Rate Constants for the Reactions of the OH Radical with (CH3) 2NH, 

(CH3) 3N, and c 2H5NH2 over the Temperature Range 298-426 K. 

Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Pitts Jr., J.N. 

(1982). 

Int. J. Chem. Kinet. 1!, 839-847. 

Rate Constants for the Gas-Phase Reaction of OH Radicals with a 

Series of Ketones at 299 ± 2 K. 

Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M. 

(1982a). 

Int. J. Cham. Kinet. 1!, 919-926. 

Kinetics of the Gas-Phase Reactions of OH Radicals with Alkyl Nitrates at 299 ± 2 K. 

Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M.; Pitts 

Jr., J.N. (1982b). 

Int. J. Chem. Kinet •. l!, 781-788. 

Kinetics of the Reactions of OH Radicals with n-Alkanes at 299 ± 

2 K. 

Atkinson, R.; carter, W.P.L.; Aschmann, S.M.; Winer, A.M.; Pitts 

Jr., J.N. (1984). 

Int. J. Chem. Kinet. ~' 469-481. 

Kinetics of the Reactions of OH Radicals with a Series of Alkanes 

at 297 ± 2 K. 

Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M.; Pitts 

Jr., J.N. (1984b). 

Int. J. Chem. Kinet. ~, 1085-1101. 

Formation of Alkyl Nitrates from the Reaction of Branched and 

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-141-

REPORT DOCUMENTATION 1. REPORT NO. 2. 

PAGE EPA-744-R-93·001 

3. Recipient's Accession No. 

5. Report Date 

January 1993 

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