Micellar catalysis on 1,10-phenanthroline promoted hexavalent chromium oxidation of ethanol

Abstract

The kinetics and mechanism of Cr(VI) oxidation of ethanol in the presence and absence of 1,10-phenanthroline in aqueous acid media have been carried out. Monomeric species of Cr(VI) are kinetically active in the absence of phen, while in the phen catalyzed path, the Cr(VI)-phen complex has been suggested as the active oxidant. In the catalyzed path, the Cr(VI)-phen complex participates in the oxidation of ethanol and ultimately is converted into the Cr(III)-phen complex. In the uncatalyzed path, the Cr(VI)-substrate ester experiences an acid catalyzed redox decomposition in the rate-determining step. The uncatalyzed path shows a second-order dependence on [H⁺], while the phen catalyzed path shows a first-order dependence on [H⁺]. Both the uncatalyzed and phen-catalyzed paths show first-order dependence on [ethanol]_T and [Cr(VI)]_T. The phen-catalyzed path is first order in [phen]_T. These observations remain unaltered in the presence of externally added surfactants. CPC inhibits the reactions while SDS catalyzes the reactions. The observed miceller effects have been explained by considering partitioning of the reactants between the miceller and aqueous phase.

Keywords:

• Chromium
• 1,10-Phenanthroline
• Ethanol
• Micellar catalysis

Acknowledgments

The authors are thankful to CSIR, New Delhi, India for providing financial support.