Theoretical study of the NO 3 radical reaction with CH 2 ClBr, CH 2 ICl, CH 2 BrI, CHCl 2 Br, and CHClBr 2 .

The potential reaction of the nitrate radical (NO 3 ), the main nighttime atmospheric oxidant, with five alkyl halides, halons (CH 2 ClBr, CH 2 ICl, CH 2 BrI, CHCl 2 Br, and CHClBr 2 ) has been studied theoretically. The most favorable reaction corresponds to a hydrogen atom transfer. The stationary points on the potential energy surfaces of these reactions have been characterized. The reactions can be classified into two groups based on the number of hydrogen atoms in the halon molecules (1 or 2). The reactions with halons with only one hydrogen atom show more exothermic profiles than those with two hydrogen atoms. In addition, the kinetics of the reaction of NO 3 + CH 2 BrI was studied in much higher detail using a multi-well Master Equation solver as a representative example of the nitrate radical reactivity against these halocarbons. These results indicate that the chemical lifetime of the alkyl halides would not be substantially affected by nitrate radical reactions, even in the case of NO 3 -polluted atmospheric conditions.