Kinetics of the reactions of OH with several alkyl halides

The rate coefficients for the reactions of OH with methyl chloride (k(1)), ethyl chloride (k(2)), methylene chloride (k(3)), ethyl bromide (k(4)), n-p ropyl bromide (k(5)) and isopropyl bromide (k(6)) were measured over the te mperature range, 220-380 K, using pulsed photolysis-pulsed laser induced fl uorescence (PP-PLIF). The measured rate coefficients, k(1-6), (cm(3) molecu le(-1) s(-1)) are : k(1) = 1.3 x 10(-13) T-0.5 exp[-(1238)/T]; k(2) = 1.5 x 10(-13) T-0.5 exp[-637/T]; k(3) = 6.6 x 10(-14) T-0.5 exp[-721/T]; k(4) = 1.7 x 10(-13) T-0.5 exp[-641/T]; k(5) = 9.1 x 10(-14) T-0.5 exp[-157/T]; k( 6) = 7.0 x 10(-14) T-0.50 exp[-145/T]. These rate constants are compared wi th those from previous studies. Some trends in the reactivities are also no ted. The globally averaged atmospheric lifetime for methyl chloride, CH3Cl, with respect to loss by reaction with OH, derived from the rate constant d ata performed in this study is 1.3 years. The rate constants for the reacti on of OH with the other compounds presented in this study are large enough to make these reactions their dominant atmospheric loss pathway.