Showing papers by "Janet Arey published in 2002"

Reactions of hydroxyl radicals and ozone with acenaphthene and acenaphthylene

Abstract: Acenaphthene and acenaphthylene are polycyclic aromatic hydrocarbons (PAHs) emitted into the atmosphere from a variety of incomplete combustion sources such as diesel exhaust. Both PAHs are present in the gas phase under typical atmospheric conditions and therefore can undergo atmospheric gas-phase reactions with the hydroxyl (OH) radical and for acenaphthylene with ozone. Using a relative rate method, rate constants have been measured at 296 ± 2 K for the OH radical reactions with acenaphthene and acenaphthylene of (in units of 10-11 cm3 molecule-1 s-1) 8.0 ± 0.4 and 12.4 ± 0.7, respectively, and for the O3 reaction with acenaphthylene of (1.6 ± 0.1) × 10-16 cm3 molecule-1 s-1. The products of the gas-phase reactions of acenaphthene and acenaphthylene and their fully deuterated analogues have been investigated using in situ atmospheric pressure ionization tandem mass spectrometry (API-MS) and gas chromatography-mass spectrometry (GC-MS). The major products identified from the OH radical-initiated reactio...

Rate Constants for the Gas-Phase Reactions of a Series of Alkylnaphthalenes with the Nitrate Radical

Abstract: Naphthalene and its C1- and C2-alkyl derivatives are semivolatile polycyclic aromatic hydrocarbons expected to be in the gas phase in ambient atmospheres and subject to degradation by gas-phase reactions with the hydroxyl (OH) radical. Using a relative rate method, rate constants for the gas-phase reactions of OH radicals with a series of alkylnaphthalenes have been measured at 298 +/- 2 K and at atmospheric pressure of air. The compounds studied include naphthalene, 1- and 2-methylnaphthalene (1-, 2-MN), 1- and 2-ethylnaphthalene (1-, 2-EN), and the 10 dimethylnaphthalene isomers (1,2-; 1,3-; 1,4-; 1,5-; 1,6-; 1,7-; 1,8-; 2,3-; 2,6-; and 2,7-DMN). Using 1,2,3-and 1,3,5-trimethylbenzene as reference compounds, the rate constant obtained for the OH radical reaction of naphthalene was (2.39 +/- 0.09) x 10(-11) cm3 molecule(-1) s(-1). Relative to naphthalene, the rate constants measured for the alkylnaphthalenes were (in units of 10(-11) cm3 molecule(-1) s(-1), where the errors given are two standard deviations and include the above uncertainty in the naphthalene rate constant) 1-MN, 4.09 +/- 0.20; 2-MN, 4.86 +/- 0.25; 1-EN, 3.64 +/- 0.41; 2-EN, 4.02 +/- 0.55; 1,2-DMN, 5.96 +/- 0.55; 1,3-DMN, 7.49 +/- 0.39; 1,4-DMN, 5.79 +/- 0.36; 1,5-DMN, 6.01 +/- 0.35; 1,6-DMN, 6.34 +/- 0.36; 1,7-DMN, 6.79 +/- 0.45; 1,8-DMN, 6.27 +/- 0.43; 2,3-DMN, 6.15 +/- 0.47; 2,6-DMN, 6.65 +/- 0.35; 2,7-DMN, 6.87 +/- 0.43. These data show that, under atmospheric conditions, the DMN isomers react most rapidly with the OH radical with calculated lifetimes of 1.9-2.4 h, followed by the MNs and ENs with lifetimes of 2.9-3.8 h and naphthalene with a lifetime of 5.8 h. These differences in reactivity were confirmed by the nighttime/daytime concentration ratios of the alkylnaphthalenes measured in ambient Riverside, CA, samples.

Products of reaction of OH radicals with α‐pinene

Abstract: [1] Products of the gas-phase reaction of α-pinene with OH radicals in the presence of NO have been investigated using gas chromatography with flame ionization detection to quantify pinonaldehyde and in situ atmospheric pressure ionization mass spectrometry in the negative ion mode to quantify selected other products as their NO2− adducts by utilizing C6-dihydroxycarbonyls and C6-hydroxynitrates formed in situ from the reaction of OH radicals with 1-hexene as an internal standard. The products quantified, and their molar formation yields, were: pinonaldehyde, 28 ± 5%; molecular weight 184 product (dihydroxycarbonyl), 19% (with an estimated uncertainty of a factor of ∼2); molecular weight 200 product, 11% (with an estimated uncertainty of a factor of ∼2). Together with a very approximate yield from our API-MS analyses for the formation of organic nitrates (∼1%) and literature data for acetone (plus coproducts), ∼65–70% of the reaction products and pathways are accounted for.

Reactions of stabilized criegee intermediates from the gas-phase reactions of O3 with selected alkenes

Abstract: The gas-phase reactions of O3 with 1-octene, trans-7-tetradecene, 1,2-dimethyl-1-cyclohexene, and α-pinene have been studied in the presence of an OH radical scavenger, primarily using in situ atmospheric pressure ionization tandem mass spectrometry (API-MS), to investigate the products formed from the reactions of the thermalized Criegee intermediates in the presence of water vapor and 2-butanol (1-octene and trans-7-tetradecene forming the same Criegee intermediate). With H3O+(H2O)n as the reagent ions, ion peaks at 149 u ([M + H]+) were observed in the API-MS analyses of the 1-octene and trans-7-tetradecene reactions, which show a neutral loss of 34 u (H2O2) and are attributed to the α-hydroxyhydroperoxide CH3(CH2)5CH(OH)OOH, which must therefore have a lifetime with respect to decomposition of tens of minutes or more. No evidence for the presence of α-hydroxyhydroperoxides was obtained in the 1,2-dimethyl-1-cyclohexene or α-pinene reactions, although the smaller yields of thermalized Criegee intermediates in these reactions makes observation of α-hydroxyhydroperoxides from these reactions less likely than from the 1-octene and trans-7-tetradecene reactions. Quantifications of 2,7-octanedione from the 1,2-dimethyl-1-cyclohexene reactions and of pinonaldehyde from the α-pinene reactions were made by gas chromatographic analyses during reactions with cyclohexane and with 2-butanol as the OH radical scavenger. The measured yields of 2,7-octanedione from 1,2-dimethyl-1-cyclohexene and of pinonaldehyde from α-pinene were 0.110 ± 0.020 and 0.164 ± 0.029, respectively, and were independent of the OH radical scavenger used. Reaction mechanisms are presented and discussed. © 2001 Wiley Periodicals, Inc. Int J Chem Kinet 34: 73–85, 2002

Products of the OH radical‐ and O3‐initiated reactions of myrcene and ocimene

Abstract: [1] We have investigated products formed from the gas-phase reactions of OH radicals and O3 (at 296 ± 2 K and 740 Torr total pressure of purified air) with the biogenic organic compounds myrcene and ocimene, using gas chromatographic analyses. In addition to the formation of acetone the OH radical reaction with myrcene in the presence of NO resulted in the formation of 4-vinyl-4-pentenal in 19 ± 4% yield, while the corresponding ocimene reaction showed no formation of the analogous product 4-methyl-3,5-hexadienal (<2% yield). The O3 reactions with myrcene and ocimene in the presence of an OH radical scavenger formed acetone (21 ± 3%) and 4-vinyl-4-pentenal (70 ± 13%) from myrene, and acetone (24 ± 4%) and 4-methyl-3,5-hexadienal (33 ± 6%) from ocimene. Reaction pathways leading to these products are discussed.

Products and mechanism of the reaction of OH radicals with 2,2,4-trimethylpentane in the presence of NO.

Abstract: Alkanes are important constituents of gasoline fuel and vehicle exhaust, with branched alkanes comprising a significant fraction of the total alkanes observed in urban areas Using a relative rate method, a rate constant for the reaction of OH radicals with 2,3,4-trimethylpentane of (684+/-012) x 10(-12) cm3 molecule(-1) s(-1) at 298+/-2 K was measured, where the indicated error is two least-squares standard deviations and does not include the uncertainty in the rate constant for the n-octane reference compound Products of the gas-phase reaction of OH radicals with 2,3,4-trimethylpentane in the presence of NO at 298+/-2 K and atmospheric pressure of air have been investigated using gas chromatography with flame ionization detection (GC-FID), combined gas chromatographymass spectrometry (GC-MS), and in situ atmospheric pressure ionization tandem mass spectrometry (API-MS) Products identified and quantified by GC-FID and GC-MS were (molar yields given in parentheses): acetaldehyde (47+/-6%), acetone (76+/-11%), 3-methyl-2-butanone (41+/-5%), 3-methyl-2-butyl nitrate (16+/-02%), and 2-propyl nitrate (62+/-08%) These compounds account for 69+/-6% of the reaction products, as carbon Additional products observed by API-MS analyses using positive and negative ion modes were C5- and C8-hydroxynitrates and a C8-hydroxycarbonyl, which, together with the predicted formation of octyl nitrates, account for some or all of the remaining products The product distribution is compared to those for the linear and branched C8-alkanes n-octane and 2,2,4-trimethylpentane