Reaktivität von Koordinationsverbindungen XX : Redoxverhaiten von Oxo-3,5-disulfobrenzcatechinato-vanadium(V)

Abstract

The oxydation of pyrocatechole-3,5-disulfonic acid by vanadium(V) in acidic solution has been studied spectrophotometrically. Analysis of kinetic data suggests two parallel reaction paths: (a) An initially formed intensely coloured VO₂⁺ substrate complex reacts monomolecularily to give a semiquinone intermediate which is rapidly oxidized to the quinone by a second VO₂⁺. (b) The VO₂⁺-substrate complex is attacked directly by a second VO₂⁺ yielding the quinone and 2 VO₂⁺. Catalysis by Fe³⁺ is explained by reaction of the corresponding iron(III)-chelate of the substrate with VO₂⁺.