Osmium(VIII) catalyzed oxidation of an antibiotic drug chloramphenicol by hexacyanoferrate(III) in aqueous alkaline medium: A mechanistic approach

The kinetics of osmium(VIII) catalyzed oxidation of antibiotic drug chloramphenicol by hexacyanoferrate(III) in aqueous alkaline medium was studied spectrophotometrically at 25°C. The reaction between chloramphenicol and hexacyanoferrate(III) in alkaline medium exhibits 1:2 stoichiometry (CHP:HCF(III)). The reaction is first order in [HCF(III)] and [Os(VIII)] and apparently less than unit order in [CHP] and [OH⁻] under the experimental conditions. The main oxidation products were identified by TLC and characterized by GCMS, IR, and ¹H NMR spectra. The active species for the catalyst and oxidant have been identified. Probable mechanism are proposed and discussed. The activation parameters with respect to the slow step of the mechanism were computed and thermodynamic quantities are calculated.