4) Orban, M.; Kijrb, E. K b b , E.; Noyes, R. M. J. Am. Chem. Soc. 1972, 94, Trans. 1992,88, 917. S = 2 k~l / k~6 / &~3 &~ = 9.52 x 10" b = 2kB6kB9[R]/k~lkW[BrOS-] = 0.545 K 3 k~z / k~l = 1.6 6 = k~l / 2 k~6 = 3.33 x r = k~i k~a / k~k~s = 0.101 Q = 2 k~s k~/ k~, ' = 0.0101 0 = kB,/kB6 = 1.667 x lo3 B = k~3 / 2 k~6 = 500 T,,, = kW[Br03-]trea = 3.91t,/s Repistry No. BrO,-, 15541-45-4; gallic acid, 149-91-7; ferroin, 14708-99-7.Timaresolved fluorescmCe detection Of Cl(9j) following 266-nm laser flash photd~is Of Cl~cO/CH$CH~(DMS)/N~ mixtures has been employed to study the kinetics of the title reaction over the temperature and pressure ranges 240-421 K and 3-700 Torr. The reaction is found to be very fast, occumng on essentially every C1(2PJ) + DMS encounter. The reaction rate increases with decreasing temperature and shows a significant pressure dependence. At 297 K, for example, the rate coefficient increases from a low-pressure limit value of approximately 1.8 X cm3 molecule-' s-' to a value of (3.3 f 0.5) X cm3 molecule-' s-l at P = 700 Torr. A few experiments were carried out with CD3SCD3 or C2H5SC2Hs replacing DMS as the sulfide reactant; within experimental uncertainty, no dependence of the rate coefficient on the identity of the sulfide reactant was observed. In a separate study, time-resolved tunable diode laser spectroscopic detection of HCl has been coupled with 248-nm laser flash photolysis of Cl&O/DMS/COz/Nz mixtures to measure the HCl product yield from the title reaction as a function of pressure at T = 297 K. The HCl yield approaches unity as P -0 but decreases with increasing pressure to a value of -0.5 at P = 203 Torr. The yield experiments demonstrate that hydrogen abstraction is the dominant reaction mechanism in the low-pressure limit. With increasing pressure, stabilization of a (CH3)gCI adduct apparently becomes competitive with the hydrogen abstraction pathway. The fate of the stabilized adduct remains highly uncertain, although it clearly does not dissociate to Cl(9J) or HCl on the time scale of our experiments (several milliseconds). The potential role of the title reaction in marine atmospheric chemistry is discussed.