Studies on the oxidation of levofloxacin by N-bromosuccinimide in acidic medium and their mechanistic pathway

Abstract

Kinetics and mechanism of oxidation of levofloxacin(LF) by N-bromosuccinimide (NBS) have been studied in acid medium with pH and ionic strength at 25°C. It is a first order reaction with respect to both LF and NBS, but inverse first order in succinimide (reduction product of NBS). The stoichiometry of the reaction is 1:2 in this investigation. The effects of added products, halide ion and ionic strength have also been investigated. Polymerization was not observed with acrylonitrile. The main oxidation products as, (3S)-9-fluoro-3-methyl-10-(4-methylpiperazin-1-yl)-5,7-dioxo-2,3,6,7-tetrahydro-5H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxylic acid and succinimide were identified by Fourier transform infrared spectroscopy (FTIR), Liquid chromatography–mass spectrometry (LC–MS), Nuclear magnetic resonance (NMR) and Thin-layer chromatography (TLC) data. The rate of reaction was examined with reference to variation of ionic strength, solvent polarity, free radicals, halides ions, mercuric acetate for fix up the Br− in reaction mixture and also addition of the product succinamide (RNH).·On the basis of the experimental results, the mechanism of the reaction has been proposed and supported by kinetic orders, spectrophotometric evidence and negative entropy of activation parameters.