Electrochemical oxidation of the dianion of bidurenol

Abstract

Electrochemical oxidation of the dianion of bidurenol (2,2',3,3',5,5',6,6'-octamethyl-4,4'-biphenol) has been studied at a glassy carbon electrode in benzonitrile solvent. The dianion 3 2- was produced in situ by deprotonaton of bidurenol with tetra-n-butylammonium hydroxide. Two oxidation peaks appear in cyclic voltammograms. The first has an associated reduction peak on the return scan but this peak is rather small. The second oxidation peak is irreversible. Controlled potential electrolysis at the second peak requires removal of two electrons per molecule of dianion. The principal product is bidurenol, postulated to result from hydrogen atom abstraction by the highly reactive twisted form of neutral 3. The first oxidation peak has been assigned to reversible oxidation of 3 2- to the radical anion 3 -. . The latter species takes part in a reversible dimerization reaction and cyclic voltammograms have been fitted by digital simulation according to this dimerization mechanism. The properties of the highly hindered diphenoquinone redox series 3, 3 -. , 3 2- are contrasted with the behavior of unhindered diphenoquinones.