Reaction of OH with Dimethyl Sulfide (DMS). 1. Equilibrium Constant for OH + DMS Reaction and the Kinetics of the OH·DMS + O2 Reaction

The formation of a weakly bound adduct in the reaction of OH with DMS- d 6 was observed between 217 and 240 K using the technique of pulsed laser photolysis/pulsed laser-induced fluorescence. The equilibrium constant for this process, OH + DMS- d 6 ↔ OH·DMS- d 6, was measured as a function of temperature. The bond strength of this adduct was determined to be 10.7 ± 2.5 kcal mol -1 . The weakly bound adduct was observed to react rapidly with O 2 . The rate constant for the reaction OH·DMS- d 6 + O 2 → products was determined to be (1.00 ± 0.33) × 10 -12 cm 3 molecules -1 s -1, independent of pressure and temperature. The atmospheric implications of the formation of this adduct and its reaction with O 2 to the mechanism of DMS oxidation in the atmosphere are discussed.