Mechanism of Oxidation of Paracetamol by Bromamine-B in Acid Medium: A Kinetic Approach

Abstract

The kinetics of oxidation of paracetamol (PAM) by sodium
N-bromobenzenesulfonamide (bromamine-B or BAB) in HClO₄
medium has been studied at 303 K. The reaction is of first-order in
[BAB] and of fractional-order each with respect to [PAM] and
[H⁺]. The variation of ionic strength and the addition of the reaction
product, benzenesulfonamide, and halide ions had no significant
effect on the reaction rate. Decrease in dielectric constant of medium
increases the rate and the solvent isotope effect was studied using
D₂O. The rates were determined at different temperatures and the
activation parameters for the overall reaction have been computed.
Michaelis-Menten type of kinetics is observed and activation
parameters for the rate-limiting step have also been computed.
4-Amino-2,6-dibromophenol was identified as the oxidation product
of PAM. Mechanism (scheme) consistent with the observed
kinetic data has been proposed and discussed.