One-step three-electron oxidation of tartaric and glyoxylic acids by chromium(VI) in the absence and presence of manganese(II)

Abstract

Kinetics of the initial stages of oxidation of tartaric acid (TA) in the absence and presence of manganese(II) ions have been studied spectrophotometrically. The rate of the induction was slow and then gradually increased with increasing [TA] and/or [HClO4]. The reaction followed third-order kinetics; first-order with respect to each of [TA], [HClO4] and [CrVI]. The kinetic and manganese(II) effect studies are consistent with a one-step three-electron mechanism (CrVI → CrIII without passing through CrIV as an intermediate) in which a termolecular complex is formed between TA, MnII and HCrO4−. In order to obtain further insight, oxidation of glyoxylic acid (GA), an oxidation product of TA, was also studied under the similar conditions. Details of the process are discussed.