Investigation of the Atmospheric Oxidation Pathways of Bromoform and Dibromomethane:  Initiation via UV Photolysis and Hydrogen Abstraction

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 108; no. 35; pp. 7247 - 7252
• Main Authors: McGivern, W. Sean, Kim, Hahkjoon, Francisco, Joseph S, North, Simon W
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.09.2004
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp0311613

A computational study of the oxidation of CH2Br2 and CHBr3 initiated via both UV photolysis and abstraction of an H atom by OH/Cl radicals has been performed. We have calculated the energetics associated with the addition of O2 to the substituted bromomethyl radicals and the subsequent addition of NO to the peroxy radicals to form energized peroxy nitrite molecules. The peroxy nitrite molecules are predicted to dissociate rapidly to form alkoxy radicals (CH2BrO and CHBr2O) and NO2, and the kinetics of these reactions have been determined using Rice−Ramsperger−Kassel−Marcus/master equation calculations. We additionally find that the reaction of the peroxy radicals with HO2 may directly lead to significant production of alkoxy radicals, a pathway that is unimportant in nonbrominated analogues. We predict that the alkoxy radicals will dissociate rapidly via C−Br bond cleavage. The atmospheric implications of these results will be discussed.