KINETIC-STUDY OF THE REACTION OF BRO RADICALS WITH DIMETHYLSULFIDE

The kinetics and mechanism of the reaction of BrO with dimethylsulfide (DMS) have been studied by the mass spectrometric discharge-flow meth od in the temperature range (233-320) K and at a total pressure-around 1 torr. The temperature dependence of the reaction rate constant k(1) = (1.5 +/- 0.4) x 10(-14) exp [(845 +/- 175)/T] cm(3) molecule(-1) s( -1) has been determined under pseudo-first-order conditions in excess of DMS over BrO radicals. Mass spectrometric calibration of the reacti on product dimethylsulfoxide (DMSO) allowed for a determination of the branching ratio of (0.94 +/- 0.11) for the DMSO forming channel. Thes e data indicate that the reaction is likely to proceed through a chann el involving a long-lived intermediate: BrO + CH3SCH3 --> [CH3S(OBr)CH 3] --> CH3S(O)CH3 + Br. The atmospheric application of the data is br iefly discussed. (C) 1996 John Wiley & Sons. Inc.