Gas-phase reactions of dimethyl selenide with ozone and the hydroxyl and nitrate radicals

Experiments were carried out in a large-volume chamber to investigate the products of the atmospherically important reactions of dimethyl selenide. Dimethyl selenoxide [(CH3)(2)SeO] was observed as the major product of the gas-phase reaction of dimethyl selenide with ozone, with an estimated yield of similar to 90%. Significant fragmentation via Se-C bond breakage occurred during the reactions of dimethyl selenide with the OH radical and the NO3 radical as indicated by HCHO formation yields of similar to 40 and similar to 60%, respectively. The spectra of the Se-containing products from both the reactions with the OH radical (in the presence of NOx) and the NO3 radical are consistent with the formation of nitrate salts, which are postulated to be [CH3Se(OH)(2)](+) NO3- and [(CH3)(2)SeOH](+) NO3-, which could arise from the intermediate formation of methaneseleninic acid [CH3Se(O)OH] and dimethyl selenoxide and their ensuing reactions with HNO3.