A Mechanistic Study on Kinetics of Oxidation of Diazepam by N Bromosuccinimide in Acid Medium

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.