Correlation of electrochemical and quantum chemical data for reduction of halogen derivatives of benzene and biphenyl

Abstract

Electrochemical splitting of the sp2 hybrid carbon-halogen bond was chosen as a typical example of an irreversible electrode reaction. It was shown in the series of chloro derivatives of benzene and biphenyl and bromo derivatives of benzene that the correlation of the electrochemical reduction potentials with the energies of the lowest unoccupied π-orbital are in these cases not physically grounded, whereas correlations with quantum-chemical parameters characterizing the carbon-halogen bond turned out to be real. Most suitable is the correlation with Wheland's localization energies calculated with the assumption of separating the carbon-halogen group from the total delocalized π-electron system in forming the transition state.