Collect. Czech. Chem. Commun. 1999, 64, 1572-1582

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

William Adcock* and Dieter Lunsmann

Department of Chemistry, Flinders University of South Australia, Adelaide 5001, Australia


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, SnMe3) 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 (∆D) upon replacement of H by all the substituents (X). The ∆D values suggest significant through-space stabilizing interactions (homohyperconjugation) in the 4-X-substituted bicyclo[2.2.1]heptane radical species.

Keywords: Cyclic voltammetry; Dissociative electron transfer; 4-Substituted 1-norbornyl radicals; Spin delocalization; Radical stablilization; Electrochemistry; Reduction cleavage.