Ru(III)-EDTA catalyzed oxidation of cyclohexane by molecular oxygen

Abstract

The oxidation of cyclohexane to cyclohexanol and cyclohexanone by molecular oxygen catalyzed by Ru(III)-EDTA in the presence and absence of the micelle cetyltrimethylammonium bromide (CTAB) is reported. The investigation was carried out in the pH range 2.00-3.50 varying the temperature from 298-318 K in a 1:1 water-dioxane mixture (μ=0.1 M KNO₃). The dependence of the rate of oxidation on factors such as catalyst, substrate, molecular oxygen and pH were determined. The reaction is first order with respect to catalyst and substrate, and one-half order with respect to molecular oxygen concentrations. The rate of oxidation was found to be independent of hydrogen ion concentration. The rate of oxidation of cyclohexane increases in the presence of CTAB. Based on the kinetic data, a mechanism is proposed for the oxidation of cyclohexane to cyclohexanol and cyclohexanone. The activation energy E_a corresponding to the observed rate constants were calculated for the reaction in the presence and absence of the micelle. The activation energy of the oxidation was found to be favourable by about 13 Kcal mol⁻¹ in the presence of CTAB.