Asian J. Research Chem. 6 (12): December 2013 1124 ISSN 0974-4169 www.ajrconline.org RESEARCH ARTICLE Silver (I) catalyzed and uncatalyzed oxidation of levofloxacin with aqueous chlorine: A comparative kinetic and mechanistic approach Raviraj M. Kulkarni*, Manjunath S. Hanagadakar and Ramesh S. Malladi Department of Chemistry, KLS Gogte Institute of Technology, Belgaum- 590 008, Karnataka, India, *Corresponding Author E-mail: ravirajmk@git.edu, manju.hanagadakar@gmail.com ABSTRACT: The kinetics and mechanism of the Ag (I) ion catalyzed reaction of levofloxacin (LFC) by free available chlorine (FAC) during water chlorination processes was investigated for the first time between the pH values 4.2 and 8.2. The pH dependent second order rate constants were found to decrease with increase in pH. (e.g. Apparent second order rate constant for Ag (I) catalyzed reaction , k ” app = 114.40 dm -3 mol -1 sec -1 at pH 4.2 and k ” app. = 8.72 dm -3 mol -1 sec -1 at pH 8.2 and at 25±0.2 0 C). The reaction rates revealed that Ag (I) catalyzed reaction was about six-fold faster than the uncatalyzed reaction. The products of the reaction were determined by Liquid chromatography and high resolution mass spectrometry. The reaction proceeds via formation of intermediate complex between Ag (I) ion and levofloxacin, then HOCl reacts with the complex to form chlorinated product. The effect of catalyst, effect of initially added product, effect dielectric constant and effect ionic strength on the rate of reaction was also studied. The effect of temperature on the rate of the reaction was studied at four different temperatures and rate constants were found to increase with increase in temperature and the thermodynamic activation parameters E a , H # , S # and G # were evaluated for the reaction and discussed. KEY WORDS: Kinetics, Chlorination, Levofloxacin, Mechanism, Silver (I), Catalysis, Oxidation. INTRODUCTION: Levofloxacin (LFC) is class of fluoroquinolone antibacterial agent. Antibacterial agents are the most important compounds used in medicine. Although, antibiotics have been used in large quantities for some decades, the existence of these substances in the environment has got little attention 1 . LFC has higher renal clearance and greater renal concentration and has optimal choice for the treatment of complicated urinary tract infections. N N Structure of levofloxacin(LFC) H 3 C F N O CH 3 O C OH O Received on 07.10.2013 Modified on 24.10.2013 Accepted on 02.11.2013 © AJRC All right reserved Asian J. Research Chem. 6(12): December 2013; Page 1124-1132 Recently the pharmaceuticals of which antibacterial groups are important, which, have been also considered as environmental contaminants 2 .Continuous exposure of antibiotic drugs to bacterial communities, promotes the bacteria to develop antibiotic resistance power. The possible induction of antibiotic resistance in bacteria is directly related to human health. The behavior of antibiotic drugs during water treatment process clearly plays a significant role in this aspect 3 . The behavior of fluoroquinolones moiety containing drugs plays an important role during water treatment process 4,5 . Mechanisms of fluoroquinolone resistance include one or two of the three main mechanistic categories, alterations in the drug target, and alterations in the permeation of the drug to reach its target. No specific quinolone-modifying or - degrading enzymes have been found as a mechanism of bacterial resistance to fluoroquinolones, although some fungi can degrade fluoroquinolones by metabolic pathways 6 . Transition metals catalyze many oxidation–reduction reactions since they involve multiple oxidation states. Recently the use of transition metal ions such as silver, ruthenium, osmium, palladium, manganese, chromium, iridium, copper either alone or as binary mixtures, as