Kinetic and Mechanistic Study of the Atmospheric Chemistry of Muconaldehydes

摘要

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 atmospheric chemistry of several muconaldehydes, photolysis and reactions with OH and O_3,have been investigated in a 1080-L reaction chamber at 298 ± 2 K using in situ FT-IR spectroscopy. Rate coefficients have 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-hexadiene-dial, 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, in all cases, E-butenedial and glyoxal and in the case of E,E-2-methyl-2,4-hexadienedial also methylglyoxal. Muconaldehydes have been postulated as intermediates in the oxidation of alkylated benzenes; if formed in this oxidation, their major atmospheric sink will be reaction with OH radicals.