Theoretical study of the NO3 radical reaction with CH2 ClBr, CH2 ICl, CH2 BrI, CHCl2 Br, and CHClBr

Abstract

The potential reaction of the nitrate radical (NO3), the main nighttime atmospheric oxidant, with five alkyl halides, halons (CH2ClBr, CH2ICl, CH2BrI, CHCl2Br, and CHClBr2) 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 + CH2 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 NO3 -polluted atmospheric conditions. ; IA: This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (PGC2018- 094644-B-C22) and Comunidad de Madrid (P2018/EMT-4329 AIRTEC-CM). Thanks are also given to the CTI (CSIC) for their continued computational support. This study received funding from the European Research Council Executive Agency under the European Union's Horizon 2020 Research and Innovation Programme (Project ERC-2016-COG 726349 CLIMAHAL) ; Peer reviewed