Kinetics of the oxidation of formic acid by aquacobalt(III) ions in aqueous perchlorate media

Abstract

The rate of oxidation of formic acid by Co^III_aq has been measured in aqueous perchlorate media over a wide range of conditions using conventional and stopped-flow spectrophotometry. The order in [Co^III] is unity and the order in [HCOOH] lies between zero and unity; the rate decreases with increasing acidity in a complex manner. The mechanism is resolved into two rate determining processes, each involving an intermediate Co^III—HCOOH complex. These two complexes have an acid–base relationship involving two protons. Values for ΔH^* and ΔS^* together with the ratio of rates of oxidation of HCOOH and DCOOH are compared for a range of oxidizing ions.