Atmospheric Chemistry of 2‐Ethyl Acrolein

AbstractThe atmospheric oxidation of the unsaturated aldehyde 2‐ethyl acrolein, CH2=C(C2H5)CHO, has been studied in laboratory experiments involving the reaction of ozone with 2‐ethyl acrolein in the dark (with cyclohexane added to scavenge the hydroxyl radical), and the sunlight irradiation of 2‐ethyl acrolein with NO in air. The major carbonyl products of the 2‐ethyl acrolein reaction with ozone are formaldehyde, acetaldehyde, and the dicarbonyl ethylglyoxal, CH3CH2COCHO. Sunlight irradiation of 2‐ethyl acrolein and NO led to the formation of three carbonyls (formaldehyde, acetaldehyde, and ethylglyoxal) and three peroxyacyl nitrates, (RC(O)OONO2), including PAN (R = CH3), PPN (R = C2H5), and the unsaturated compound EPAN (R = CH2=C(C2H5)). Mechanisms are outlined for the reactions of ozone and of the hydroxyl radical with 2‐ethyl acrolein. These mechanisms are consistent with the observed carbonyl and peroxyacyl nitrate products. Thermal decomposition, a major atmospheric removal process for peroxyacyl nitrates, has been studied for EPAN. The decomposition rate of EPAN relative to that of PAN is 0.59–0.73 at 292–294 K and 1 atm of air. Atmospheric implications of these results a