An FTIR product study of the photooxidation of dimethyl disulfide

The products of the 254 nm photolysis of ppm levels of DMDS have been studied as a function of the O sub(2) partial pressure at 760 Torr (N sub(2) + O sub(2)) and 298 plus or minus 2 K. The major sulfur containing compounds detected were SO sub(2) and CH sub(3)SO sub(3)H (methane sulfonic acid, MSA) and the major carbon containing compounds were CO, HCHO, CH sub(3)OH and CH sub(3)OOH (methyl hydroperoxide). Within the experimental error limits the observed sulfur and carbon balances were approximately 100%. CH sub(3)OOH has been observed for the first time in such a photooxidation system. Its observation provides evidence for the formation of CH sub(3) radicals by the further oxidation of the CH sub(3)S radicals formed in the primary photolysis step. Some of the possible implications of the results of this study for the degradation mechanisms of other atmospherically important organic sulfur compounds, in particular DMS, are briefly considered.