Web Release Date: August 4,
Kinetics and Products of Photolysis and Reaction with OH Radicals of a Series of Aromatic Carbonyl Compounds
and
Air Pollution Research Center, University of California, Riverside, California 92521
Received for review April 28, 2006
Revised manuscript received July 4, 2006
Accepted July 11, 2006
Abstract:
We have investigated the photolysis and OH radical reactions of phthaldialdehyde, 2-acetylbenzaldehyde, and 1,2-diacetylbenzene, atmospheric reaction products of naphthalene and alkylnaphthalenes, and of phthalide, a photolysis product of phthaldialdehyde. Using a relative rate method with 1,2,4-trimethylbenzene and 2,2,3,3-tetramethylbutane as reference compounds, measured rate constants for the gas-phase OH radical reactions (in units of 10-12 cm3 molecule-1 s-1) were as follows: phthaldialdehyde, 23 ± 3; 2-acetylbenzaldehyde, 17 ± 3; 1,2-diacetylbenzene, <1.2; and phthalide, <0.8. Blacklamp irradiation showed that phthaldialdehyde and 2-acetylbenzaldehyde photolyze, and, combined with absorption spectra measured in n-hexane solution, average photolysis quantum yields of 0.19 and 0.21, respectively, were derived (290-400 nm). No evidence for photolysis of 1,2-diacetylbenzene or phthalide by blacklamps was obtained. The major atmospheric loss process of phthaldialdehyde and 2-acetylbenzaldehyde are estimated to be by photolysis, with photolysis lifetimes of 1.4-1.5 h for a 12-hr average NO2 photolysis rate of 0.312 min-1. Phthalic anhydride was the major observed product from the OH radical-initiated reactions of all four compounds and was also formed from photolysis of phthaldialdehyde and 2-acetylbenzaldehyde. The major photolysis products observed were phthalide from phthaldialdehyde and 3-methylphthalide from 2-acetylbenzaldehyde.
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