KINETIC AND MECHANISTIC STUDY OF THE ATMOSPHERIC CHEMISTRY OF MUCONALDEHYDES

2,4-Hexadienedial and its alkylated derivatives, often referred to as muconaldehydes, have been postulated as primary ring cleavage products in the oxidation of simple alkylated aromatics. Some aspects of the a tmospheric chemistry of several muconaldehydes, photolysis and reactio ns with OH and O-3, have been investigated in a 1080-L reaction chambe r at 298 +/- 2 K using in situ FT-IR spectroscopy. Rate coefficients h ave been determined for the reaction of OH radicals with the following muconaldehydes using the relative kinetic method (in units of 10(-12) cm(3) molecules(-1) s(-1)): E,E-2,4-hexadienedial, 88 +/- 3; E,Z-2,4- hexadienedial, 109 +/- 11; E,E-2-methyl-2,4-hexadienedial, 118 +/- 2. The major products of both the OH radical and the O-3 reactions are, i n all cases, E-butenedial and glyoxal and in the case of E,E-2-methyl- 2,4-hexadienedial also methylglyoxal. Muconaldehydes have been postula ted as intermediates in the oxidation of alkylated benzenes; if formed in this oxidation, their major atmospheric sink will be reaction with OH radicals.