AN IN-SITU UV-VIS AND IR SPECTROELECTROCHEMICAL STUDY OF THE DISPOSITION OF A HYDROQUINONE ANION SALT ON PLATINUM-ELECTRODES FROM DICHLOROMETHANE SOLUTIONS

Cyclic voltammetry with a platinum electrode of hydroquinone (BQH(2)) solutions in dichloromethane, containing tetrabutylammonium perchlorat e supporting electrolyte, shows a sharp asymmetric irreversible oxidat ion peak at about -0.3 V (SCE). This feature is seen, in addition to t he expected features in this system, when the cycle is extended to pot entials more negative than -0.6 V (SCE). Cyclic voltammetry, in situ U V-vis and infrared spectroelectrochemistry have shown that hydroquinon e anion (BQH(-)) is formed at negative potentials and this appears to arise via surface decomposition of hydroquinone to p-benzosemiquinone (BQH(-)) followed by reaction of BQH(.) with the p-benzoquinone radica l anion (BQ(.-)). The sharp asymmetric peak in the cyclic voltammogram s is due to oxidation of the hydroquinone anion in the insoluble tetra butylammonium salt on the electrode surface. The oxidation of BQH(-) a ppears to occur via disproportionation of BQH(-) and leads to BQH, and p-benzoquinone (BQ) as the products. (C) 1998 Elsevier Science S.A.