ATMOSPHERIC CHEMISTRY OF 2-ETHYL ACROLEIN

The 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 cyclohe xane added to scavenge the hydroxyl radical), and the sunlight irradia tion of 2-ethyl acrolein with NO in air. The major carbonyl products o f the 2-ethyl acrolein reaction with ozone are formaldehyde, acetaldeh yde, and the dicarbonyl ethylglyoxal, CH3CH2COCHO. Sunlight irradiatio n of 2-ethyl acrolein and NO led to the formation of three carbonyls ( formaldehyde, acetaldehyde, and ethylglyoxal) and three peroxyacyl nit rates, (RC(O)OONO2), including PAN (R = CH3), PPN (R = C2H5), and the unsaturated compound EPAN (R = CH2C(C2H5). Mechanisms are outlined for the reactions of ozone and of the hydroxyl radical with 2-ethyl acrol ein. These mechanisms are consistent with the observed carbonyl and pe roxyacyl nitrate products. Thermal decomposition, a major atmospheric removal process for peroxyacyl nitrates, has been studied for EPAN. Th e decomposition rate of EPAN relative to that of PAN is 0.59-0.73 at 2 99-294 K and 1 atm of air. Atmospheric implications of these results a re discussed.