Catalytic Activity of Ruthenium(III) and Thermodynamic Study of Oxidative Degradation of Chloramphenicol by Cerium(IV) in Sulfuric Acid Medium

摘要

The micro amounts of ruthenium(III) catalyzed oxidation of chloramphenicol by cerium(IV) in an aqueous sulphuric acid medium has been studied spectrophotometrically at 25 A degrees C and at I = 1.60 mol center dot dm(-3). The order with respect to [Ce(IV)] and [Ru(III)] was found to be unity. Increasing [H+] accelerates the rate with less than unit order in [H+]. The reaction rate decreases with increasing ionic strength and increases with decreasing dielectric constant of the medium. The experimental results suggest that the active species of cerium(IV) and ruthenium(III) were CeSO4 (2+) and [Ru(H2O)(6)](3+), respectively. Based on the experimental results a suitable mechanism was proposed and the rate law was derived. The activation parameters were calculated with respect to the slow step of the proposed mechanism and thermodynamic quantities were also determined. The reaction constants involved in the mechanism have been computed. There is a good agreement between the experimental and calculated rate constants under different experimental conditions.