Article,
Atmospheric chemistry of CH2Br2: Rate coefficients for its reaction with Cl atoms and OH and the chemistry of the CHBr2O radical
International Journal of Chemical Kinetics, 28 (6): 433--442 (January 1996)
Abstract
Rate coefficients for the reaction of OH radicals and Cl atoms with dibromomethane, OH + CH2Br2 --> CHBr2 + H2O (1) and Cl + CH2Br2 --> CHBr2 + HCl (3), and for the reaction of Cl atoms with methyl bromide, Cl + CH3Br --> HCl + CH2Br (4), have been obtained using relative rate techniques. At 298 K, the value of k(1) was determined to be (1.2 +/- 0.3) x 10(-13) cm(3) molec(-1) s(-1). The rate coefficients k(3) and k(4) were determined at a series of temperatures ranging from 228 K to 296 K and combined with the measurements of Gierczak et al., yielding the following Arrhenius expressions for k(3) and k(4); k(3) = (6.35 +/- 0.6) x 10(-12) exp(-807 +/- 50/T) cm(3) molec(-1) s(-1) and k(4) = (1.49 +/- 0.2) x 10(-11) exp(-1056 +/- 50/T) cm(3) molec(-1) s(-1).In addition, the Cl atom initiated oxidation mechanism of CH2Br2 in air has been studied at 298 K. The products observed were HC(O)Br and small amounts of CO. The dominant atmospheric fate of the alkoxy radical, CHBr2O, is elimination of a Br atom, which occurs at the rate estimated to be greater than 4 x 10(6) s(-1) in 700 torr of O-2 at 298 K. (C) 1996 John Wiley & Sons, Inc.
Tags
- bromine,
- chlorine,
- depletion,
- flash-photolysis
- kinetics,
- methanes,
- organic-compounds,
- oxidation,
- ozone
- polar
- substituted
- sunrise,
- temperature,
