ON THE ELECTROREDUCTION MECHANISM OF HALOBENZENES .1. A QUANTUM CHEMICAL APPROACH

The half-wave potentials of various halobenzene derivatives in aprotic solvents correlate with the charge on the halogen atom being reduced and with the energy of the first unoccupied sigma molecular orbital, calculated using the MNDO method. These correlations explain the ortho effect observed in the dihalogen derivatives. Open-shell calculations of the radical anions demonstrate their existence as metastable intermediates. Chlorobenzene has been chosen as a model in order to study the breaking of the C-X bond by the reaction coordinate method. According to these results, two possible reduction mechanisms are discussed.