Redox properties and bond dissociations energies of phenoxyl radicals

Abstract

Reduction half-wave potentials of several phenoxyl radicals have been measured by photomodulated voltammetry in acetonitrile. Two of the investigated radicals exhibit a reversible behavior, but for the others a rather quasi-reversible nature of the heterogeneous electron transfer has to be considered. The measured reduction half-wave potentials are within 70 mV of reported values for formal one-electron potentials of the phenolate–phenoxyl couples. That is why one can assume that the values of half-wave reduction potentials are close to the standard potentials of the electrochemical reactions. Differences of the bond dissociation energy (BDE)(OH), for the substituted phenols relative to the BDE(OH) of the phenol were calculated and compared with corresponding data in the gas-phase.