Experimental and theoretical studies on the oxidation of lomefloxacin by alkaline permanganate

Abstract

The kinetic and mechanistic investigation of oxidation of emerging contaminant lomefloxacin (LMF) by alkaline permanganate was carried out spectrophotometrically. The oxidation product 7-amino-1-ethyl-6, 8-difluoro-4-oxo-quinoline-3-carboxylic acid was identified by Agilent 6130 Series Quadrupole LC/MS. The stoichiometry was found to be 1:2, that is, 1 mol of lomefloxacin reacted with 2 mol Mn(VII). Orders with respect to [LMF] and [OH− ] were found to be fractional and less that one. The oxidation reaction proceeds via an alkali permanganate species that forms a complex with lomefloxacin and the complex then decomposes to give the product. The rate of reaction was found to decrease with decrease in the dielectric constant. The effects of initially added products and ionic strength have also been investigated. The kinetics of the reaction was also studied at four different temperatures, and the thermodynamic activation parameters for the reaction were evaluated and discussed. The geometry optimization of reactants and activated complex were carried out using density functional theory (DFT). The DFT calculations were accomplished with the TURBOMOLE program package (Version-6.4). The activation energy was found to be ~21 kJ/mol at RI-BP86.def 2-TZVPP level of theory