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ISRN Physical Chemistry
Volume 2013 (2013), Article ID 738932, 10 pages
http://dx.doi.org/10.1155/2013/738932
Research Article

Oxidative Cleavage of β-Lactam Ring of Cephalosporins with Chloramine-T in Alkaline Medium: A Kinetic, Mechanistic, and Reactivity Study

Department of Post-Graduate Studies in Chemistry, Bangalore University, Central College Campus, Bangalore Karnataka 560 001, India

Received 21 February 2013; Accepted 28 March 2013

Academic Editors: I. Anusiewicz, J. M. Farrar, and E. B. Starikov

Copyright © 2013 Anu Sukhdev et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Cephalosporins are β-lactam antibiotics, and the important drugs of this group are cephalexin, cefadroxil and cephradine. In the present research, the kinetics and mechanism of oxidation of cephalexin (CEX), cefadroxil (CFL), and cephradine (CPD) with chloramine-T (CAT) in alkaline medium were investigated at 301 K. All the three oxidation reactions follow identical kinetics with a first-order dependence each on [CAT]o and [substrate]o. The reaction is catalyzed by hydroxide ions, and the order is found to be fractional. The dielectric effect is negative. Proton inventory studies in H2O-D2O mixtures with CEX as a probe have been made. Activation parameters and reaction constants have been evaluated. Oxidation products were identified by mass spectral analysis. An isokinetic relation was observed with β = 378 K, indicating that enthalpy factors control the rate. The rate increases in the following order: CPD > CFL > CEX. The proposed mechanism and the derived rate law are consistent with the observed kinetics.