Iodide ion mediated oxidation of chloramphenicol by hexacyanoferrate(III) ion in aqueous alkaline medium
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Iodide ion mediated oxidation of chloramphenicol by hexacyanoferrate(III) ion in aqueous alkaline medium Mallavva Bolattin • Radha Vernekar • Arunkumar Kiragi • Kirthi Byadagi • Sharanappa Nandibewoor • Shivamurti Chimatadar
Received: 20 May 2013 / Accepted: 26 July 2013 Ó Akade´miai Kiado´, Budapest, Hungary 2013
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. Keywords Kinetics Chloramphenicol Hexacyanoferrate(III) ion Iodide ion Oxidation Mechanism
Electronic supplementary material The online version of this article (doi:10.1007/s11144-0130618-6) contains supplementary material, which is available to authorized users. M. Bolattin R. Vernekar A. Kiragi K. Byadagi S. Nandibewoor S. Chimatadar (&) P. G. Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, India e-mail: [email protected]
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Introduction Chloramphenicol (2,2-dichloro-N-[(1R,2R)-hydrox(hydroxylmethyl)nitrophenyl) ethyl]acetamide) is a bacteriostatic antimicrobial. Chloramphenicol (CHP) is effective against a wide variety of Gram positive and Gram negative bacteria, including most anaerobic organisms. It is considered as a prototypical broad band spectrum antibiotic, alongside the tetracyclines. The clinical application of chloramphenicol was in the treatment of typhoid. The most serious adverse effect associated with chloramphenicol treatment is bone marrow toxicity. Due to its extensive usage, chloramphenicol may enter the environment via waste water effluent and biosolids from sewage treatment plants and via manure and litters from food producing animal husbandry. The presence and accumulation of chloramphenicol antibiotics in aquatic environments, albeit at low concentrations, may pose threats to the ecosystem and human health by inducing increase and spread of bacteria drug resistance due to long
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