Iodide ion mediated oxidation of chloramphenicol by hexacyanoferrate(III) ion in aqueous alkaline medium

Abstract

The iodide ion mediated oxidation of chloramphenicol by hexacyanoferrate(III) ion in an aqueous alkaline medium at constant ionic strength of 1.10 mol dm−3 was studied spectrophotometrically at 25 °C. The kinetics was followed under pseudo-first order conditions by taking chloramphenicol concentration excess over the concentration of hexacyanoferrate(III) ion. The reaction showed first order kinetics with respect to hexacyanoferrate(III) ion, the catalyst, and iodide ion concentrations. The order with respect to chloramphenicol and alkali concentrations was found to be less than unity. Added products hexacyanoferrate(II) ion and p-nitro benzaldehyde did not have any significant effect on the rate of reaction. The effect of variation of ionic strength and dielectric constant were also studied on the rate of reaction. Based on the experimental results, a suitable free radical mechanism is proposed and the rate law is derived. The activation parameters were calculated and discussed with respect to the slow step of the proposed mechanism. 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.