Atmospheric Degradation of Volatile Organic Compounds - American


Air Pollution Research Center and Department of Environmental Sciences, University of California, Riverside, California 92521. Received February 11, 2...
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Chem. Rev. 2003, 103, 4605−4638

4605

Atmospheric Degradation of Volatile Organic Compounds Roger Atkinson*,† and Janet Arey Air Pollution Research Center and Department of Environmental Sciences, University of California, Riverside, California 92521 Received February 11, 2003

Contents 1. Introduction 2. Tropospheric VOC Transformation Processes 2.1. Initial Reactions and Lifetimes 2.2. Reaction Mechanisms 3. Atmospheric Chemistry of Alkanes 3.1. Kinetic Data for the Initial OH Radical and NO3 Radical Reactions 3.2. Reaction Mechanism 3.2.1. Reactions of Organic Peroxy (RO2•) Radicals 3.2.2. Reactions of Alkoxy (RO•) Radicals 3.2.3. Subsequent Reactions of 1,4-Hydroxycarbonyls 4. Atmospheric Chemistry of Alkenes 4.1. Rate Constants for the Initial Reactions of Alkenes with OH and NO3 Radicals and O3 4.2. Mechanism of the OH Radical Reaction 4.3. NO3 Radical Reaction 4.4. Reaction with O3 5. Aromatic Hydrocarbons 5.1. Kinetics of the OH Radical Reactions 5.2. Reactions of Phenols 5.3. Reactions of Unsaturated 1,4-Dicarbonyls and Di-Unsaturated 1,6-Dicarbonyls 6. Atmospheric Reactions of Oxygenated VOCs 6.1. Aldehydes 6.2. Ketones 6.3. Aliphatic Alcohols 6.4. Ethers 6.5. Alkyl Nitrates 7. Conclusions and Future Research Needs 7.1. Needed Research 7.1.1. Experimental Studies 7.1.2. Theoretical Studies and Critical Reviews and Evaluations 8. Acknowledgments 9. Note Added in Proof 10. References

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sources,1-5 and may also be formed in situ in the atmosphere as products of the atmospheric transformations of other VOCs. On a worldwide basis, emission of VOCs from biogenic sources (mainly vegetation) dominates, with estimated emissions being 1150 Tg (C) per year from vegetation2 and ∼100 Tg (C) per year from anthropogenic sources.1 Although on a worldwide basis VOCs from biogenic sources dominate over those from anthropogenic sources by a factor of ∼10, in urban areas anthropogenic VOCs often dominate. The major classes of emitted VOCs are alkanes, alkenes, aromatic hydrocarbons, and oxygenated compounds, with vegetative emissions typically being composed of alkenes (isoprene, monoterpenes, and sesquiterpenes) and oxygenated VOCs (including 2-methyl-3-buten-2-ol, acetone, methanol, cis-3-hexen1-ol, cis-3-hexenyl acetate, and camphor)2,3,6 and anthropogenic emissions resulting from vehicle emissions (comprising mainly gasoline constituents, including, in the U.S., the ethanol and methyl tert-butyl ether oxygenates added to the fuel) and emissions from, for example, landfills, refineries, petrochemical sources, solvent usage, and industrial facilities. In urban air in cities such as Los Angeles, CA and Boston, MA, the nonmethane VOCs are typically made up of the following: alkanes, 40-45%; alkenes, 10%; aromatic hydrocarbons, 20%; and oxygenates, 10-15%; plus unidentified VOCs.7,8 As noted, the alkane and aromatic hydrocarbon fractions of these urban air nonmethane VOCs often have a composition generally similar to that of gasoline. In the atmosphere, VOCs from both anthropogenic and biogenic sources undergo a number of physical and chemical processes leading to their removal from the atmosphere or transformation in the atmosphere.9 Physical removal of VOCs to the earth’s surface may occur by dry deposition and wet deposition. These processes have been discussed in detail elsewhere10,11 and are not dealt with here. The chemical processes leading to the atmospheric degradation of VOCs are the subject of this article.

2. Tropospheric VOC Transformation Processes 2.1. Initial Reactions and Lifetimes

1. Introduction Volatile organic compounds (VOCs) are emitted into the atmosphere from anthropogenic and biogenic * To whom correspondence should be addressed. Phone: (909) 7874191. Fax: (909) 787-5004. E-mail: [email protected] † Also Department of Chemistry.

In the troposphere, VOCs are transformed by the chemical processes of photolysis (at wavelengths >290 nm because shorter wavelengths are absorbed by O2 and O3 in the stratosphere), reaction with the hydroxyl (OH) radical (typically during daylight hours), reaction with the nitrate (NO3) radical during

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Roger Atkinson was born in the U.K. and received a Ph.D. in Physical Chemistry from the University of Cambridge in 1969. He is presently a Research Chemist at the Air Pollution Research Center and Distinguished Professor in the Department of Environmental Sciences and the Department of Chemistry at the University of California at Riverside.

Janet Arey received a B. S. in Chemistry from the Massachusetts Institute of Technology in 1971 and a Ph.D. in Environmental Health Sciences from the University of Michigan in 1980. She is presently a Research Chemist at the Air Pollution Research Center and Professor in the Department of Environmental Sciences at the University of California at Riverside.

evening and nighttime hours, reaction with O3, and in coastal and marine areas reaction with Cl atoms during daylight hours.9 The sources of OH radicals, NO3 radicals, Cl atoms, and O3 in the troposphere are discussed elsewhere9,12 and hence are not dealt with here. Rate constants for the gas-phase reactions of alkanes, alkenes, aromatic hydrocarbons, aliphatic and aromatic aldehydes, ketones, alcohols, hydroperoxides, selected ethers, and alkyl nitrates are listed in Table 1 (OH radical reactions), Table 2 (O3 reactions), and Table 3 (NO3 radical reactions). All of the alkanes, alkenes, aromatic hydrocarbons, aldehydes (RCHO, where R ) alkyl or aryl), ketones (RC(O)R′, where R and R′ are alkyl), alcohols (ROH, where R ) alkyl), hydroperoxides, and alkyl nitrates for which apparently reliable data are available are included in Tables 1-3. Also included in these tables are rate data for the unsaturated carbonyls methyl vinyl ketone, methacrolein, and 3-isopropenyl-6-oxo-heptanal, and the dicarbonyls glyoxal, methylglyoxal, pinonaldehyde, and caronaldehyde. The rate constants and temperature-dependent parameters listed in Tables 1-3 are, wherever pos-

Atkinson and Arey

sible, taken from reviews and evaluations.8,13-16,29,30 Temperature-dependent rate expressions are given as the Arrhenius expression, k ) Ae-B/T, or (especially for the reactions of OH radicals with alkanes) as the three-parameter expression k ) ATne-B/T, with n often being set at 2.13,29,30 For VOCs not included in these reviews and evaluations8,13-16,29,30 or for which new data now exist that supersede previous recommendations, data are listed in Tables 1-3 from selected, apparently reliable, studies. Data obtained from relative rate studies have been reevaluated, when necessary, to be consistent with recent recommendations for the reference compound(s) used. It needs to be pointed out that the rate data for those VOCs in Tables 1-3 not referenced to the recent reviews and evaluations of Atkinson,13 Calvert et al.,8,15 and IUPAC16 have not undergone recent critical evaluation. Thus, for the VOCs reviewed and evaluated by Atkinson29,30 (and even for certain VOCs included in Calvert et al.8,15), rate constants obtained from relative rate studies may require reevaluation. Rate constants for the reactions of a VOC with OH radicals, NO3 radicals, Cl atoms, and O3 can be combined with measured, computed, or estimated tropospheric concentrations of OH radicals, NO3 radicals, Cl atoms, and O3 to provide lifetimes of the VOC with respect to each of these potential transformation processes. Such calculated lifetimes depend on the temperature (or, equivalently, altitude) assumed, and on the concentrations of OH radicals, NO3 radicals, Cl atoms, and O3 used. Additionally, absorption cross-sections and photolysis quantum yields (both as a function of wavelength) can be combined with the actinic flux (again as a function of wavelength) to obtain the photolysis rate of the VOC (if it absorbs at wavelengths >290 nm and has a nonzero quantum yield for chemical change). Table 4 gives calculated lower tropospheric (298 K) lifetimes of selected VOCs from anthropogenic and biogenic sources with respect to reaction with OH radicals, NO3 radicals, and O3. Additionally, as noted above, certain VOCs (formaldehyde and acetone among those listed in Table 1) undergo photolysis. It should be recognized that Cl atom reactions may also be an important VOC transformation process in certain locales such as in the Arctic troposphere during springtime, and possibly in some coastal regions.60 However, on a global basis Cl atom reactions are believed to be of minor importance as a VOC loss process61-63 and, therefore, are not included in this article. For those interested, the kinetics and initial reaction mechanisms of the reactions of Cl atoms with eC4 VOCs are evaluated on an ongoing basis by the NASA64 and IUPAC16 evaluations, and rate constants for reactions of Cl atoms with alkanes and alkenes (as of 1997) are listed in Atkinson.14 Because the temperature in the troposphere varies from ∼200 K (upper troposphere) to ∼300 K (lower troposphere), it is desirable to have kinetic data over this temperature range. Furthermore, as noted below for alkenes and, especially, aromatic hydrocarbons, useful mechanistic information can be obtained for the OH radical reactions from kinetic studies conducted at elevated temperatures (>600 K in the case

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Table 1. Room-Temperature Rate Constants, Temperature-Dependent Parameters, and Temperature Ranges over Which These Rate Expressions Are Applicable for the Gas-Phase Reactions of OH Radicals with Alkanes, Alkenes, Aromatic Hydrocarbons, Aldehydes, Ketones, Alcohols, Hydroperoxides, Selected Ethers, and Alkyl Nitrates organic

1012 x k (298 K) (cm3 molecule-1 s-1)

methane methane-d1 methane-d2 methane-d3 methane-d4 ethane propane n-butane 2-methylpropane n-pentane 2-methylbutane 2,2,-dimethylpropane n-hexane 2-methylpentane 3-methylpentane 2,2-dimethylbutane 2,3-dimethylbutane n-heptane 2,4-dimethylpentane 2,2,3-trimethylbutane n-octane 2,2,4-trimethylpentane 2,3,4-trimethylpentane 2,2,3,3-tetramethylbutane n-nonane 3,3-diethylpentane n-decane 3,4-diethylhexane n-undecane n-dodecane n-tridecane n-tetradecane n-pentadecane n-hexadecane cyclopropane isopropylcyclopropane cyclobutane cyclopentane cyclohexane methylcyclohexane n-butylcyclohexane cycloheptane cyclooctane bicyclo[2.2.1]heptane bicyclo[2.2.2]octane bicyclo[3.3.0]octane cis-bicyclo[4.3.0]nonane trans-bicyclo[4.3.0]-nonane cis-bicyclo[4.4.0]decane trans-bicyclo[4.4.0]-decane tricyclo[5.2.1.02,6]decane tricyclo[3.3.1.13,7]decane trans-pinane tricyclene quadricyclane

0.00640 0.00528 0.00340 0.00195 0.000916 0.248 1.09 2.36 2.12 3.80 3.6 0.825 5.20 5.2 5.2 2.23 5.78 6.76 4.77 3.81 8.11 3.34 6.6 0.972 9.70 4.8 11.0 6.92 12.3 13.2 15.1 17.9 (312 K) 20.7 (312 K) 23.2 (312 K) 0.0815c 2.61 2.03 4.97 6.97 9.64 14.7 12.4 13.3 5.12 13.7 10.3 16.0 16.5 18.6 19.0 10.6 21.5 12.4 2.66 1.70

ethene propene 1-butene cis-2-butene trans-2-butene 2-methylpropene 1-pentene cis-2-pentene trans-2-pentene 2-methyl-1-butene 3-methyl-1-butene 2-methyl-2-butene

8.52 26.3 31.4 56.4 64.0 51.4 31.4 65 67 61 31.8 86.9

A (cm3 molecule-1 s-1)

B (K)

temperature range (K)

2 2 2 2 2 2

987 1322 1926 1972 1882 499 87 -114 -213 -158

195-1234 249-422 270-354 270-354 244-800 180-1225 190-1220 231-753 213-1146 224-753

1.86 × 10-17 2.54 × 10-14

2 1

207 112

3.37 × 10-11 1.66 × 10-17 1.95 × 10-17

2 2

809 -407 -406

245-328 247-1220 299-1086a

9.20 × 10-18 2.72 × 10-17 2.35 × 10-17

2 2 2

-459 -361 -140

1.99 × 10-17 2.53 × 10-17

2 2

178 -436

243-753 299-1078 297-1186 243-313b 290-1180 295-1097a

3.17 × 10-17

2

-406

296-1109a

4.21 × 10-18

2

454

2.10 × 10-17 2.73 × 10-17 3.26 × 10-17

2 2 2

-25 -214 -262

272-366 273-1194 292-497

3.99 × 10-17 5.91 × 10-17

2 2

-373 -276

298-388 298-387

Alkenes 1.96 × 10-12 4.85 × 10-12 6.55 × 10-12 1.10 × 10-11 1.01 × 10-11 9.47 × 10-12

-438 -504 -467 -487 -550 -504

291-425 293-467d 295-424e 295-425f 295-425f 295-425

5.32 × 10-12 1.92 × 10-11

-533 -450

295-423 295-426

Alkanes 1.85 × 10-20 3.19 × 10-18 2.18 × 10-12 1.46 × 10-12 5.70 × 10-18 1.49 × 10-17 1.65 × 10-17 1.81 × 10-17 1.17 × 10-17 2.52 × 10-17

n 2.82 2

287-901 292-962

200-459

ref 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15

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Table 1. (Continued) organic

1012 x k (298 K) (cm3 molecule-1 s-1)

A (cm3 molecule-1 s-1)

n

B (K)

temperature range (K)

ref

Alkenes (Continued) 1-hexene 2-methyl-1-pentene 2-methyl-2-pentene trans-4-methyl-2- pentene 3,3-dimethyl-1-butene 2,3-dimethyl-2-butene 1-heptene trans-2-heptene 2,3-dimethyl-2-pentene trans-4,4-dimethyl-2-pentene trans-4-octene propadiene 1,2-butadiene 1,3-butadiene 1,2-pentadiene cis-1,3-pentadiene 1,4-pentadiene 2-methyl-1,3-butadiene (isoprene) 3-methyl-1,2-butadiene trans-1,3-hexadiene trans-1,4-hexadiene 1,5-hexadiene cis- and trans-2,4-hexadiene 2-methyl-1,4-pentadiene 2-methyl-1,3-pentadiene 4-methyl-1,3-pentadiene 2,3-dimethyl-1,3-butadiene 2-methyl-1,5-hexadiene 2,5-dimethyl-1,5-hexadiene 2,5-dimethyl-2,4-hexadiene cis-1,3,5-hexatriene trans-1,3,5-hexatriene myrcene ocimene (cis- and trans-) cyclopentene cyclohexene 1,3-cyclohexadiene 1,4-cyclohexadiene cycloheptene 1,3-cycloheptadiene 1,3,5-cycloheptatriene 1-methyl-1-cyclohexene bicyclo[2.2.1]-2-heptene bicyclo[2.2.1]-2,5-heptadiene bicyclo[2.2.2]-2-octene camphene 2-carene 3-carene limonene R-phellandrene β-phellandrene R-pinene β-pinene sabinene R-terpinene γ-terpinene terpinolene R-cedrene R-copaene β-caryophyllene R-humulene longifolene benzene toluene ethylbenzene o-xylene m-xylene p-xylene n-propylbenzene isopropylbenzene

37 63 89 61 28 110 40 68 103 55 69 9.82 26 66.6 35.5 101 53 100 57 112 91 62 134 79 136 131 122 96 120 210 110 111 215 252 67 67.7 164 99.5 74 139 97 94 49 120 41 53 80 88 164 313 168 52.3 74.3 117 363 177 225 67 90 197 293 47

7.66 × 10-12

-74

295-478

1.48 × 10-11

-448

295-483

2.7 × 10-11

-390

249-422

4.28 × 10-11

-401

294-363

1.21 × 10-11 1.55 × 10-11

-436 -467

294-364 294-364

193 -338

239-342 213-383

0 0

250-315 296-335

Aromatic Hydrocarbons 1.22 2.33 × 10-12 5.63 1.18 × 10-12 7.0 13.6 23.1 2.31 × 10-11 14.3 1.43 × 10-11 5.8 6.3

14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 16 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 17,18 14,15 14,15 17,18 17,18 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 14,15 8 8 8 8 8 8 8 8

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Table 1. (Continued) organic o-ethyltoluene m-ethyltoluene p-ethyltoluene 1,2,3-trimethylbenzene 1,2,4-trimethylbenzene 1,3,5-trimethylbenzene tert-butylbenzene 4-isopropyltoluene hexamethylbenzene indan indene tetralin styrene R-methylstyrene β-methylstyrene β,β-dimethylstyrene naphthalene biphenyl formaldehyde acetaldehyde propanal butanal 2-methylpropanal pentanal 2-methylbutanal 3-methylbutanal 2,2-dimethylpropanal hexanal 2-methylpentanal 3-methylpentanal 4-methylpentanal 3,3-dimethylbutanal 2-ethylbutanal heptanal benzaldehyde o-tolualdehyde m-tolualdehyde p-tolualdehyde glyoxal methylglyoxal methyl vinyl ketone methacrolein pinonaldehyde caronaldehyde 3-isopropenyl-6-oxo-heptanal acetone 2-butanone 2-pentanone 3-pentanone 3-methyl-2-butanone 2-hexanone 3-hexanone 3-methyl-2-pentanone 4-methyl-2-pentanone 3,3-dimethyl-2-butanone 2-heptanone 5-methyl-2-hexanone 2,4-dimethyl-3-pentanone 2-octanone 2-nonanone 2,6-dimethyl-4-heptanone 2-decanone cyclobutanone cyclopentanone cyclohexanone camphenilone nopinone sabinaketone camphor

1012 x k (298 K) (cm3 molecule-1 s-1)

A (cm3 molecule-1 s-1)

n

Aromatic Hydrocarbons (Continued) 11.9 18.6 11.8 32.7 32.5 56.7 4.5 14.5 113 19 78 34 58 51 57 32 23.0 1.56 × 10-11 7.1 9.37 15 20 24 26 28 33 27 28 30 33 29 26 21 40 30 12 18 17 13

Aldehydes 1.20 × 10-14 4.4 × 10-12 5.1 × 10-12 6.0 × 10-12 7.3 × 10-12 9.9 × 10-11

1

4.3 × 10-11

Dicarbonyls and Unsaturated Carbonyls 11 15 20 2.6 × 10-12 29 8.0 × 10-12 44 48 110 0.17 1.22 4.4 2.0 2.9 9.1 6.9 6.9 13 1.2 11 10 5.0 11 12 26 13 0.87 2.9 6.4 4.8 15 4.9 4.3

B (K)

temperature range (K)

-117

294-366

-287 -365 -405 -410 -390 -310

228-1205 202-348 240-372 258-422 243-423 243-410

-560

243-425

-610 -380

232-378 234-373

g -503

202-395 240-440

1.58 × 10-12

-193

253-372

7.9 × 10-13

-834

253-372

1.33 × 10-12

-649

263-372

Ketones g 2.53 × 10-18

2

ref 8 8 8 8 8 8 8 8 19 8 8 8 8 8 8 8 8 8 16 16 16 16 20,21 20-23 23 20,23 20,21,23 22,23 23 23 23 23 23 24 25 25 25 25 16 16 16 16 26,27 26 28 16 16 29-31 29,30 32 29,30 29,30 33 29,30,32 29 31 32 29 29 29 29 29 29 29 29 30 28,30 26 34

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Table 1. (Continued) organic

1012 x k (298 K) (cm3 molecule-1 s-1)

methanol ethanol 1-propanol 2-propanol 1-butanol 2-butanol 2-methyl-1-propanol 2-methyl-2-propanol 1-pentanol 2-pentanol 3-pentanol 3-methyl-1-butyl alcohol 3-methyl-2-butanol 2,2-dimethyl-1-propanol 1-hexanol 2-hexanol 1-heptanol 1-octanol cyclopentanol cyclohexanol

0.94 3.2 5.8 5.1 8.5 8.7 9.3 1.06 11 12 13 13 12 5.5 15 12 14 14 11 19

methyl hydroperoxide tert-butyl hydroperoxide

5.5 3.0

dimethyl ether diethyl ether methyl tert-butyl ether ethyl tert-butyl ether tert-amyl methyl ether methyl nitrate ethyl nitrate 1-propyl nitrate 2-propyl nitrate 1-butyl nitrate 2-butyl nitrate 2-methyl-1-propyl nitrate 1-pentyl nitrate 2-pentyl nitrate 3-pentyl nitrate 2-methyl-1-butyl nitrate 3-methyl-1-butyl nitrate 3-methyl-2-butyl nitrate 2,2-dimethyl-1-propyl nitrate 2-hexyl nitrate 3-hexyl nitrate 2-methyl-2-pentyl nitrate 3-methyl-2-pentyl nitrate cyclohexyl nitrate 3-heptyl nitrate 3-octyl nitrate

2.8 13.1 2.94 8.7 6.1 0.023 0.18 0.58 0.29 1.6 0.86 1.5 3.0 1.7 1.0 2.3 2.3 1.7 0.79 3.0 2.5 1.6 2.8 3.1 3.4 3.6

A (cm3 molecule-1 s-1)

B (K)

temperature range (K)

-170 -530 -70 -792 -140

235-1205 227-599 263-372 253-587 263-372

2

-321

240-440

h

h

293-764

-190

223-423

16 30

-303 -837 -483 -800 -656

230-650 230-442 230-440 234-372 231-372

16 30,43 30,43 43 43

Alkyl Nitrates 4.0 × 10-13 6.7 × 10-13

845 395

221-298 233-298

6.2 × 10-13

230

233-300

16 16 16 16 16 16 30 30 29,30 29,30 30 30 29,30 29,30 29,30 29,30 29,30 29,30 29,30 29,30 29,30

Alcohols 6.0 × 10-18 6.1 × 10-18 4.6 × 10-12 4.03 × 10-18 5.3 × 10-12 4.07 × 10-18

h

n 2 2 2

Hydroperoxides 2.9 × 10-12 Ethers 1.14 × 10-17 8.91 × 10-18 6.54 × 10-18 6.70 × 10-18 7.56 × 10-18

2 2 2 2 2

ref 16,35 16,35 16 16 16 16 36 37,38 30 29,36,39 29 36,40 29 30 41 29 29,30 30 29 42

a Data only available at room temperature and at ∼1100 K (i.e., no rate data have been measured between room temperature and ∼1100 K). b Although rate constants are available over this temperature range, no temperature-dependent rate expression is recommended.13 c Because of significantly different temperature dependencies in the studies conducted, the recommended rate expression leads to a 298 K rate constant which is 10% higher than room-temperature measurements.13 d Rate constant also available at 103 ( 9 K.44 e Rate constants are also available at 23, 44, 75, and 170 K45 and at 103 ( 9 K.44 f Rate constants are also available at 23, 44, 75, and 170 K.45 g k ) 8.8 × 10-12 e-1320/T + 1.7 × 10-14 e420/T cm3 molecule-1 s-1. h See ref 30 and references therein.

of alkenes and >450 K in the case of aromatic hydrocarbons).29,30

2.2. Reaction Mechanisms Whereas the reaction mechanism occurring in the troposphere after initial reaction of a VOC with OH

radicals, NO3 radicals, Cl atoms, and O3, or after photodissociation, depends on the specific VOC, in most cases the reaction mechanism involves formation (at least in part) of an alkyl or substituted alkyl radical (for example, hydroxyalkyl, nitrooxyalkyl [containing an -ONO2 group], or oxoalkyl [containing

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Table 2. Room-Temperature Rate Constants, Temperature-Dependent Parameters, and Temperature Ranges over Which These Data Have Been Measured for the Gas-Phase Reactions of O3 with Alkanes, Alkenes, Aromatic Hydrocarbons, Aldehydes, Ketones, Alcohols, and Selected Unsaturated Carbonyls organic all alkanes

1017 x k (298 K) (cm3 molecule-1 s-1) 37 (296 K) 14 (297 K) 0.30 (294 K) 0.93 11 (293 K) >13 (295 K) 0.40 (293 K) 0.0185 0.63 4.3 1.45 1.27 31 (294 K) 37 (294 K) 1.3 8.0 2.6 8.0 1.4 2.6 (294 K) 47 (296 K) 54 (296 K) 57 67 8.1 120 4.6 25 15 5.4 (294 K) 16 8.9 1.1 (293 K) 20.7 (296 K) 0.75 (292 K)

9.14 × 10-15 5.51 × 10-15 3.36 × 10-15 3.22 × 10-15 6.64 × 10-15 2.70 × 10-15 2.13 × 10-15 3.7 × 10-15 7.1 × 10-15 4.9 × 10-15

2580 1878 1774 968 1059 1632 1580 1002 1132 1741

178-362 235-362 225-363 225-364 225-364 225-363 240-324 278-353 278-353 278-353

6.51 × 10-15 1.62 × 10-15 3.2 × 10-15 7.6 × 10-15

829 1480 1017 1163

227-363 240-324 278-353 278-353

3.03 × 10-15

294

227-363

4.2 × 10-15

1756

278-353

1.54 × 10-15 1.34 × 10-14 2.1 × 10-15

2690 2283 1158

226-325 231-324 240-324

1.03 × 10-14

1995

242-353

6.9 × 10-15

1668

240-324

1.8 × 10-15

350

240-324

2.87 × 10-15

1063

240-324

1.3 × 10-15

494

240-324

5.25 × 10-15 2.16 × 10-15

1040 952

240-324 240-324

14-16 14-16 14,15 14,15 14,15 14,15 15 47 47 47 15 14,15 15 47 47 15 15 15 15 15 14,15 14,15 15 15 14,15 14,15 47 15 14,15 15 15 15 15 15 14,15 15 14,15 15 14,15 15 15 14,15 15 15 16 14,15 14,15 15 15 14,15 14 14,15 14,15 14,15 14,15 14,15 14,15 15 15 14,15 15 15 14,15 15 15 48 14 48

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Table 2. (Continued) organic

1017 x k (298 K) (cm3 molecule-1 s-1)

A (cm3 molecule-1 s-1)

B (K)

temperature range (K)

ref

Alkenes (Continued) bicyclo[2.2.1]-2-heptene bicyclo[2.2.1]-2,5-heptadiene bicyclo[2.2.2]-2-octene cis-cyclooctene cis-cyclodecene camphene 2-carene 3-carene limonene R-phellandrene β-phellandrene R-pinene β-pinene sabinene R-terpinene γ-terpinene terpinolene R-cedrene R-copaene β-caryophyllene R-humulene longifolene

160 360 7.1 38 2.9 0.090 (296 K) 23 3.7 21 300 4.7 8.4 1.5 8.3 2100 14 190 2.8 16 (296 K) 1160 (296 K) 1170 (296 K)