Reactions of trifluoromethyl radicals with organic halides. Part 7.—Chloro- and fluorochloro-ethanes

Abstract

The reactions of CF₃ radicals with the compounds C₂H₅Cl, CH₂ClCH₂Cl, CH₃CHCl₂, CH₃CCl₃, CHCl₂CHCl₂, CF₃CH₂Cl, CF₃CHCl₂, CF₃CCl₃, CF₂ClCFCl₂ and CH₃CF₂Cl were studied. Arrhenius parameters were measured for abstraction of H by CF₃, where the molecule contained abstractable H, and for abstraction of Cl by CF₃ from most of the multi-chlorinated molecules. Reactions of some of the chloroethanes were complicated by αβ-elimination of HCl, photosensitized by the hexafluoroacetone which was used as a source of CF₃ radicals. However, it is believed that reliable rate constants for abstraction were measured. The variations in activation energies for H and halogen abstraction are discussed in terms of polar effects and enthalpy changes. There are substantial variations in A factors for both H and halogen abstraction by CF₃ and there is a correlation between variations in A and E both for hydrogen abstraction and halogen abstraction.