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 se lenide. Dimethyl selenoxide [(CH3)(2)SeO] was observed as the major pr oduct 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 wi th the OH radical and the NO3 radical as indicated by HCHO formation y ields of similar to 40 and similar to 60%, respectively. The spectra o f the Se-containing products from both the reactions with the OH radic al (in the presence of NOx) and the NO3 radical are consistent with th e formation of nitrate salts, which are postulated to be [CH3Se(OH)(2) ](+) NO3- and [(CH3)(2)SeOH](+) NO3-, which could arise from the inter mediate formation of methaneseleninic acid [CH3Se(O)OH] and dimethyl s elenoxide and their ensuing reactions with HNO3.