Electrochemical Behavior of the Quinone-Hydroquinone

The electrochemical behavior of quinone, hydroquinone, and quinhydrone in pyridine solution at the stationary pyrolytic graphite electrode has been studied by conventional nd cyclic voltammetry. In the absence of available protons, quinone is somewhat reversibly reduced in a probable le process to a free radical anion; in the presence of protons, the free radical produced on le reduction is thought o be oxidized to an N-dihydroxyphenyl p r idinium ion. The latter is also a likely product from the oxidation of hydroquinone. The quinone-hydroquinone, system itself is irreversible, e.g., quinhydrone be-haves as a mixture of qumone and hydroquinone, the potentials of whose waves are 0.5v apart. Since the oxidation-reduction behavior of the qui-none-hydroquinone system is often used as a test sys-tem for electrochemical technics and approaches, its behavior at the pyrolytic graphite electrode was in