A spectroscopic investigation of kinetics and mechanism of ruthenium(III)-catalyzed oxidation of N-(2-hydroxyethyl)phthalimide by cerium(IV) in aqueous sulphuric acid and sulphate media

The oxidation of N-(2-hydroxyethyl)phthalimide with cerium(IV) with a small amount of ruthenium(III) present as a catalyst has been studied by spectrophotometric means. The spectroscopic study has been carried out in aqueous H 2 SO 4 and media at constant ionic strength of I = 1.60 mol dm −3 . Stoichiometric analysis shows that one mole of NHEP reacts with two moles of cerium(IV). The oxidation products were identified by IR and GC-MS. Orders with respect to substrate, oxidant, ruthenium(III) and acid concentrations were determined. Increase in sulphuric acid concentration increases the rate. Effect of ionic strength and solvent polarity of the medium on the rate of the reaction was studied. The added product, cerium(III), has no significant effect on the rate of reaction. The active species of oxidant in sulphate medium and catalyst are and [Ru(H 2 O) 6 ] 3+ . Based on the experimental results a suitable mechanism is proposed. The activation parameters and the thermodynamic quantities are also determined and discussed.