Effects of Bridgehead Substituents on the Stability of the 1-Norbornyl Radical

摘要

The electrochemical reductive cleavage of a series of 4-X-substituted bicyclo[2.2.1]heptan-1-yl bromides and iodides (X = H, F, Cl, Br, I, SnMe-3) was investigated by means of cyclic voltammetry. By application of the dissociative electron-transfer theory, the variations in the peak reduction potentials translate to values for the weakening of the C-Br and C-I bond dissociation energies (#DELTA#D) upon replacement of H by all the substituents (X). The #DELTA#D values suggest significant through-space stabilizing interactions (homohyperconjugation) in the 4-X-substituted bicyclo[2.2.1]heptane radical species.