Theoretical study of the thermal decomposition of several β-chloroalkoxy radicals

Abstract

A theoretical study of the thermal decomposition of ClCH₂CH₂O, ClCH₂CH(O)CX₃ (X = H,F) and HOCH₂CH(O)CF₃ by β C–C scission has been carried out. The geometries, frequencies and energies of the radicals and the transition states leading to their decomposition have been characterized using B3LYP theory with the 6-31G(d,p) basis set. The rate constants for the thermal decomposition have been evaluated. For the ClCH₂CH₂O and ClCH₂CH(O)CH₃ radicals the barrier to the decomposition has been found to be 17.04 and 13.38 kcal mol⁻¹, respectively. CF₃ substitution of methyl group in the ClCH₂CH(O)CH₃ and the HOCH₂CH(O)CH₃ radicals has been found to be of slight influence on their thermal decomposition, the decomposition barriers being 14.46 and 7.95 kcal mol⁻¹. Based on the estimated decomposition rate constants, the dominant fate of these β-chloroalkoxy radicals under atmospheric conditions would be the reaction with oxygen, in contrast to the corresponding β-hydroxyalkoxy radicals, for which the decomposition is the major removal process, at least in the lower troposphere.