Ruthenium(III) mediated oxidation of succinic acid by cerium(IV) in aqueous sulphuric acid medium - A kinetic and mechanistic approach

Abstract

The oxidation of succinic acid by ceriuim(IV) has been studied spectrophotometrically in aqueous sulphuric acid medium at 298 K at constant ionic strength of 1.6 mol dm ―3 . A minute amount of ruthenium(m) (10- 6 mol dm ―3 ) is sufficient to enhance the slow reaction between succinic acid and cerium(IV). The main reaction products are cerium(III) and oxaloacetic acid. The stoichiometry is 1: 4, that is [suc. acid]: [Ce IV ] = 1: 4. The reaction is first order in both cerium(IV) and ruthnium(III) concentrations. The order with respect to suc. acid concentration varies from first order to zero order, as the succinic acid concentration increases. Increase in sulphuric acid concentration decreases the reaction rate. The added sulphate and bisulpahte decreases the rate of reaction. The added product cerium(III) retards the reaction rate. The active species of oxidant and catalyst are Ce(SO 4 ) 2 and [Ru(H 2 O) 6 ] 3+ respectively. Possible mechanism is proposed. The activation parameters were determined with respect to slow step and reaction constants involved have been determined.