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 [(CH 3) 2SeO] was observed as the major product of the gas-phase reaction of dimethyl selenide with ozone, with an estimated yield of ∼ 90%. Significant fragmentation via Se-C bond breakage occurred during the reactions of dimethyl selenide with the OH radical and the NO 3 radical as indicated by HCHO formation yields of ∼ 40 and ∼ 60%, respectively. The spectra of the Se-containing products from both the reactions with the OH radical (in the presence of NO x ) and the NO 3 radical are consistent with the formation of nitrate salts, which are postulated to be [CH 3Se(OH) 2] + NO 3 − and [(CH 3) 2SeOH] + NO 3 −, which could arise from the intermediate formation of methaneseleninic acid [CH 3Se(O)OH] and dimethyl selenoxide and their ensuing reactions with HNO 3.