An in situ UV-vis and IR spectroelectrochemical study of the deposition of a hydroquinone anion salt on platinum electrodes from dichloromethane solutions

Abstract

Cyclic voltammetry with a platinum electrode of hydroquinone (BQH 2 ) solutions in dichloromethane, containing tetrabutylammonium perchlorate supporting electrolyte, shows a sharp asymmetric irreversible oxidation peak at about −0.3 V (SCE). This feature is seen, in addition to the expected features in this system, when the cycle is extended to potentials more negative than −0.6 V (SCE). Cyclic voltammetry, in situ UV-vis and infrared spectroelectrochemistry have shown that hydroquinone 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 radical anion (BQ − ). The sharp asymmetric peak in the cyclic voltammograms is due to oxidation of the hydroquinone anion in the insoluble tetrabutylammonium salt on the electrode surface. The oxidation of BQH − appears to occur via disproportionation of (BQH ) and leads to BQH 2 and p -benzoquinone (BQ) as the products.