Fragmentation of aryl halide pi anion radicals. Bending of the cleaving bond and activation vs driving force relationships.

Recent rate data for very fast cleaving of aryl chloride and bromide anion radicals may be accommodated satisfactorily within rate constant versus ArX/ArX*- standard potential existing correlations provided the standard potential is determined experimentally. Cyclic voltammetry is used for this purpose, taking careful account of the electron transfer/fragmentation reaction mixed character of the kinetics. The ensuing activation/driving force relationships allow the determination of the intrinsic barriers, the magnitude of which are discussed in the framework of a new Morse curve model that includes and emphasizes the role of bond bending.