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Atmospheric chemistry of toluene-1,2-oxide/2-methyloxepin

Lookup NU author(s): Emeritus Professor Bernard Golding

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Abstract

A kinetic and product study of the atmospheric chemistry of toluene-1,2- oxide/2-methyloxepin, a possible intermediate in the OH-initiated oxidation of toluene, was conducted in a 1080 1 quartz glass reaction chamber. The compound was found to be unstable, with a thermal decomposition lifetime of (333 ± 83) min. Photolysis with superactinic lamps (320 nm < λ < 460 nm, λ(max) = 360 nm) was found to be slow, while that with low-pressure Hg lamps (λ(max) = 254 nm) proceeded rapidly. For clear sky conditions at noon on July 1 at a latitude of 40°N, an atmospheric photolytic lifetime of (26 ± 4) min can be extrapolated from the experimental data using the superactinic lamps. For the reaction with OH radicals, a reaction rate constant of (2.1 ± 0.1 x 10-10 cm3 molecule-1 s-1 was determined; the main products were E/Z-isomers of 6-oxohepta-2,4-dienal. Reaction with NO3 radicals was observed to proceed with a rate constant of (1.27 ± 0.10) x 10-11 cm3 molecule-1 s-1; the main products were unidentified nitrogen-containing compounds. In addition, 2E,4Z-6-oxohexa-2,4-dienal was identified; other isomers are probably formed as well. The results suggest that under atmospheric conditions both photolysis and reaction with OH radicals will be important sinks for toluene-1,2-oxide/2-methyloxepin, while reaction with NO3 radicals will become important under laboratory conditions at high concentrations of NO(x), possibly also in heavily polluted tropospheric air masses.

Publication metadata

Author(s): Klotz B, Barnes I, Golding BT, Becker K-H

Publication type: Article

Publication status: Published

Journal: Physical Chemistry Chemical Physics

Year: 2000

Volume: 2

Issue: 2

Pages: 227-235

ISSN (print): 1463-9076

ISSN (electronic): 1463-9084

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/a908365k

DOI: 10.1039/a908365k

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