Kinetics and Mechanism of Ce(IV) Oxidation of Free and Coordinated Glyoxylic Acid

Abstract

Abstract The kinetics and mechanism of Ce(IV) oxidation of glyoxylic acid and pentaammineglyoxylatocobalt(III) perchlorate have been investigated in acidic sulfate media in the temperature range 35 to 50 °C and at ionic strength 0.95 M. The rate of decrease of [Ce(IV)] was found to be first order in [substrate] and [Ce(IV)]. The observed second order rate constant, kobsd for the disappearance of [Ce(IV)] is satisfactorily given by, k obsd=\frack1+k2K3[HSO4−]⁄[H+]1+K3[HSO4−]⁄[H+] (for glyoxylato complex) and k obsd=\frack11+K3[HSO4−]⁄H+] (for glyoxylic acid) Both Ce(SO4)2 and [Ce(SO4)3]2− appear to be the oxidant species for coordinated glyoxylate while for free glyoxylic acid Ce(SO4)2 seems to be the only oxidant species. The values of k1 and k2 and the associated activation parameters have been computed. A suitable mechanism has been suggested for the reaction.