Kinetics of Oxidation of Diazepam by N Bromosuccinimide in Acid Medium: A Mechanistic Study
N. Nanda *
Department of Chemistry, B M S College for Women, Basavanagudi, Bangalore 560004 India
S. Malini
Department of Chemistry, Dayananda Sagar College of Engineering, Bangalore 560078 India
Puneeth Kumar
Department of Chemistry, Dayanganda Sagar College of Biological sciences Bangalore 560 004, India
Netkal M. Made Gowda
Department of Chemistry, Western Illinois University, 1 University Circle, Macomb, Illinois 61455, U.S.A and Pooja Bhagavat Memorial Mahajana PG Centre, University of Mysore, Mysore 570 016 India
*Author to whom correspondence should be addressed.
Abstract
The oxidation of diazepam (DZ) by N-Bromosuccinimide (NBS) in aqueous acid medium follows a first-order kinetics in [NBS] and a fractional-order each on [HCl] and [DZ]. The reaction stoichiometry involves one mol NBS consumed by one mol DZ. The rate of the reaction increases with the decrease in dielectric constant of the medium. Added products and the variation of ionic strength have no significant effect on the rate of the reaction. The oxidation products were identified by spectral analysis. A mechanism involving the formation of an intermediate NBS-DZ complex has been proposed. The solvent effect is consistent with the charge dispersion going into the transition state. The activation parameters for the reaction have been determined. The negative entropy of activation suggests the formation of a rigid, associative transition state involving loss of degrees of freedom.
Keywords: Diazepam, N-bromosuccinimide, acid medium, oxidation kinetics, mechanism