Showing papers by "Roger Atkinson published in 2009"

Dicarbonyl products of the OH radical-initiated reaction of a series of aromatic hydrocarbons.

Abstract: Aromatic hydrocarbons are important constituents of vehicle exhaust and of nonmethane organic compounds in ambient urban air. We used a derivatization technique with methane positive chemical ionization gas chromatography/mass spectrometry to investigate the carbonyl products formed from the OH radical-initiated reactions of toluene, the xylenes, and the trimethylbenzenes. Characteristic diderivatized molecular ions of dicarbonyl products were obtained. Consistent with previous studies, the 1,2-dicarbonyls glyoxal, methylglyoxal, and biacetyl were observed, as were all but one of the possible unsaturated 1,4-dicarbonyl coproducts. Unsaturated 1,4-diketones had formation yields similar to their potential coproduct 1,2-dicarbonyls. However, apart from HC(O)CH=CHCHO, unsaturated 1,4-dialdehydes and keto-aldehydes were generally observed in lower yield than their potential 1,2-dicarbonyl coproducts.

Formation and reactions of 2-formylcinnamaldehyde in the OH radical-initiated reaction of naphthalene.

Abstract: 2-Formylcinnamaldehyde [O-HC(O)C6H4CH=CHCHO] is a major product of the OH radical-initiated reaction of naphthalene, the atmospherically most abundant polycyclic aromatic hydrocarbon. Previous studies indicate that 2-formylcinnamaldehyde undergoes photolysis as well as reaction with OH radicals. We have used direct air sampling atmospheric pressure ionization mass spectrometry (API-MS) to monitor 2-formylcinnamaldehyde as its protonated molecular ion during OH radical-initiated reactions of naphthalene. From the time-dependent behavior of the 2-formylcinnamaldehyde signal, ratios of (2-formylcinnamaldehyde removal rate/naphthalene reaction rate) were determined over a range of approximately 3 in (OH radical concentration/ light intensity). With an estimated rate constant for the reaction of OH radicals with 2-formylcinnamaldehyde of 5.3 x 10(-11) cm3 molecule(-1) s(-1), the photolysis rate of 2-formylcinnamaldhyde by blacklamps was determined to be approximately equal to that of NO2. Photolysis of 2-formylcinnamaldehyde will be the dominant loss process in the atmosphere, with an estimated lifetime of 2-formylcinnamaldehyde of approximately 120 s at a solar zenith angle of 30 degrees. Our data were used to re-evaluate the previous 2-formylcinnamaldehyde measurements of Sasaki et al. (Environ. Sci. Technol. 1997, 31, 3173-3179) and derive a 2-formylcinnamaldehyde formation yield from the OH radical reaction of naphthalene in the presence of NO of 56(-10)(+15)%.

Rate constants for the gas-phase reactions of OH radicals with a series of C6-C14 alkenes at 299 +/- 2 K.

Abstract: Rate constants for the gas-phase reactions of OH radicals with the C6−C14 2-methyl-1-alkenes and the C6−C10 trans-2-alkenes have been measured at 299 ± 2 K and atmospheric pressure of air using a relative rate technique. The rate constants obtained (in units of 10−11 cm3 molecule−1 s−1) were as follows: 2-methyl-1-pentene, 5.67 ± 0.21; 2-methyl-1-hexene, 6.50 ± 0.11; 2-methyl-1-heptene, 6.71 ± 0.21; 2-methyl-1-octene, 7.02 ± 0.16; 2-methyl-1-nonene, 7.28 ± 0.21; 2-methyl-1-decene, 7.85 ± 0.26; 2-methyl-1-undecene, 7.85 ± 0.21; 2-methyl-1-dodecene, 7.96 ± 0.26; 2-methyl-1-tridecene, 8.06 ± 0.37; trans-2-hexene, 6.08 ± 0.26; trans-2-heptene, 6.76 ± 0.32; trans-2-octene, 7.23 ± 0.21; trans-2-nonene, 7.54 ± 0.16; and trans-2-decene, 7.80 ± 0.26, where the indicated errors are two least-squares standard deviations and do not include the uncertainty associated with the rate constant for the reference compound α-pinene. Our data show that the rate constants for the reactions of OH radicals with 2-methyl-1-alkene...

Yields of glyoxal and ring-cleavage co-products from the OH radical-initiated reactions of naphthalene and selected alkylnaphthalenes.

Abstract: Naphthalene and alkylnaphthalenes are the most abundant polycyclic aromatic hydrocarbons present in ambient air and are transformed mainly by chemical reaction with hydroxyl (OH) radicals during daylight hours. To better understand the reaction mechanisms, we have quantified glyoxal from the OH radical-initiated reactions of naphthalene, 1-methylnaphthalene, 1,4-dimethylnaphthalene, acenaphthene, and acenaphthylene as a function of the NO(2) concentration and, for the naphthalene reaction, also in the absence of NO(2). Glyoxal was formed as a first-generation product from the naphthalene, 1-methylnaphthalene, 1,4-dimethylnaphthalene, and acenaphthene reactions, and its yields were independent of the NO(2) concentration over the ranges employed, being 5% in the presence of NO(2) and 3% in the absence of NO(2) from naphthalene; approximately 3% from 1-methylnaphthalene; approximately 2% from 1,4-dimethylnaphthalene; approximately 10-15% from acenaphthene; and <2% from acenaphthylene. Second-generation formation of glyoxal was evident in the 1-methylnaphthalene, 1,4-dimethylnaphthalene, and acenaphthene reactions. For the naphthalene reaction, our results suggest that the reactions of the OH-naphthalene adducts with NO(2) and O(2) both lead to glyoxal formation in similar yield. Simultaneous measurements of phthaldialdehyde from naphthalene, 2-acetylbenzaldehyde from 1-methylnaphthalene, and 1,2-diacetylbenzene from 1,4-dimethylnaphthalene suggest that these C(n-2)-dicarbonyls are coproducts to glyoxal.

Rate Constants for the Gas-Phase Reactions of NO3 Radicals and O3 with C6−C14 1-Alkenes and 2-Methyl-1-alkenes at 296 ± 2 K

Abstract: Rate constants for the gas-phase reactions of NO3 radicals and O3 with a series of C6−C14 1-alkenes and 2-methyl-1-alkenes have been measured at 296 ± 2 K and atmospheric pressure of air using relative rate methods. For the NO3 radical reactions, the rate constants obtained (in units of 10−14 cm3 molecule−1 s−1) were: 1-hexene, 2.00 ± 0.16; 1-octene, 2.35 ± 0.15; 1-decene, 2.55 ± 0.16; 1-dodecene, 2.79 ± 0.36; 1-tetradecene, 2.87 ± 0.21; 2-methyl-1-pentene, 43.8 ± 2.3; 2-methyl-1-hexene, 52.4 ± 2.5; 2-methyl-1-octene, 57.8 ± 2.6; 2-methyl-1-nonene, 60.8 ± 2.9; 2-methyl-1-undecene, 60.8 ± 3.3; 2-methyl-1-tridecene, 60.3 ± 3.4; and cycloheptene, 49.4 ± 2.0. For the O3 reactions, the rate constants obtained (in units of 10−17 cm3 molecule−1 s−1) were: 1-hexene, 0.898 ± 0.054; 1-heptene, 1.05 ± 0.07; 1-octene, 1.01 ± 0.04; 1-decene, 1.11 ± 0.05; 1-dodecene, 1.38 ± 0.14; 1-tridecene, 1.92 ± 0.12; 1-tetradecene, 2.44 ± 0.24; 2-methyl-1-pentene, 1.26 ± 0.13; 2-methyl-1-heptene, 1.35 ± 0.05; 2-methyl-1-octene, 1....

Effect of NO2 concentration on product yields of the gas-phase NO3 radical-initiated reaction of ethyl- and dimethyl-naphthalenes.

Abstract: Alkylnaphthalenes are minor constituents of vehicle fuels and are emitted into the atmosphere in vehicle exhaust and other sources of incomplete combustion. In the lower atmosphere, alkylnaphthalen...