Kinetics and mechanisms of the reaction of OH radicals with dimethyl sulfide

The rate constant of the reaction of OH with DMS has been measured relative to OH + ethene in a 420 l reaction chamber at 760 torr total pressure and 298 ± 3 K in N 2 + O 2 buffer gas using the 254 nm photolysis of H 2 O 2 as the OH source. In agreement with a recent absolute rate determination of the reaction the measured effective rate constant was found to increase with increasing partial pressure of O 2 in the system, for 760 torr air a rate constant of (8.0 ± 0.5) × 10 −12 cm 3 s −1 was obtained. Product studies have been performed on the reaction in air using FTIR absorption spectrometry for detection of reactants and products. On a molar basis, SO 2 was formed with a yield of 70% and dimethyl sulfone (CH 3 SO 2 CH 3 ) with a yield of approximately 20%. These results are considerably different to those obtained in other product studies which were carried out in the presence of NO x . These differences are compared and their relevance for the atmospheric oxidation mechanisms of DMS is discussed.