Chlorine abstraction reactions of fluorine. Part 3.—Thermochemical data for chlorofluoroalkanes

Abstract

The gas phase reactions of fluorine with CCl₄, CCl₃F, CCl₂F₂, CClF₃, CClF₂CClF₂ and CClF₂CF₃ have been studied. By the use of equilibrium data for the dissociation of fluorine, Arrhenius parameters are determined for the rate determining step F + R—Cl → R + ClF. The heat of this reaction is estimated for each compound by the use of reasonable assumptions as to the magnitude of the activation energy for the reverse step. The resultant heats of reaction corrected to 298 K, are used to calculate a large number of the C—Cl, C—F and C—C bond strengths for the compounds and free radicals derived from them. Theoretical values of the A factors for the rate determining step are calculated by the BEBO method, and compared with the experimentally derived values. The agreement is poor, although the theoretical values do predict the trend in A factors that was experimentally observed.