Studies of the Electrolytic Reduction Mechanism of Anthracene, Benzophenone and Anthraquinone by the Use of Polarography and Electron Spin Resonance Spectroscopy

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Abstract
The electrochemical reduction mechanism of anthracene, benzophenone and anthraquinone was studied in N,N′-dimethylformamide (DMF) and/or its water mixture by means of polarography and electron spin resonance spectroscopy (ESR). The polarograms of these compounds consisted of two well-defined waves in anhydrous DMF: the first wave corresponds to the formation of the anion radical and the second wave to the reduction of the anion radical to the dinegative anion. When water was added, the limiting current of the first wave increased at the expense of the second wave. In order to elucidate the reduction mechanism of these molecules in DMF-water mixture, the kinetic behavior of the anion radical was studied by the ESR method. It has been found that the reduction of anthracene is understood by the protonation mechanism, but that of anthraquinone is not explained by the protonation mechanism at all; the disproportionation of the anion radical must be considered. For the reduction of benzophenone both the protonation and the disproportionation mechanism must be taken into consideration.