Estimation of bond dissociation Gibbs energies for carbon–halogen bonds in anion radicals of some aryl halides and substituted benzyl halides

Abstract

A thermochemical cycle incorporating the standard potential E^o_RX/RX˙^–. of aryl halides and m- and p-substituted benzyl halides RX, the standard potential E^o_{X˙^–/X^–} of the halide ion X^– and the bond dissociation Gibbs energy ΔG^o_BDE(RX) of RX is used to determine the bond dissociation Gibbs energy ΔG^o_BDE(RX˙^–) of the carbon–halogen bond in some anion radicals RX˙^–. The values of E^o_RX/RX˙^– are not directly measurable for most benzylic substrates but can be approximated by the standard potentials for the corresponding compounds in which the CH₂X group is replaced by an H atom. The calculations are compared with experimental results and similar calculations published recently.