The atmospheric chemistry of the unsaturated aldehydes, methacrolein, acrolein, and crotonaldehyde

Unsaturated aldehydes (methacrolein, acrolein, crotonaldehyde) are present in the atmosphere as the result of the oxidation of 1,3-dienes, or due to direct emissions from anthropogenic sources. As an important first-generation product of isoprene oxidation, the tropospheric chemistry of methacrolein is well characterized. The dominant pathway for its removal is reaction with OH, which occurs with nearly equally probability via an addition and an abstraction pathway. Among the products of the abstraction reaction is an unsaturated PAN-analog, peroxymethacrylic nitric anhydride (MPAN). Data on the rate coefficient for reaction of OH with MPAN and the mechanism for the reaction of OH with acrolein and crotonaldehdye were presented. About 30% of the OH/acrolein reaction occurred via addition to the C=C double bond, while this pathway accounts for about 50% of the OH/crotonaldehyde reaction. This is an abstract of a paper presented at the 223rd ACS National Meeting (Orlando, FL 4/7-11/2002).