Mechanistic Investigation of Oxidation of Phenylpropanolamine with N‐Bromobenzenesulfonamide in Alkaline Medium: A Kinetic Approach

Ningegowda Prasad,Kikkeri N Mohana

doi:10.1155/2008/348482

Abstract

The kinetics of oxidation of phenylpropanolamine (PPA) with sodium N‐bromobenzenesulfonamide or bromamine‐B (BAB) has been investigated in alkaline medium at 308 K. The oxidation reaction obeys the rate law, – d[BAB]/dt = k [BAB] [PPA]x [OH‐], where x is less than unity. The variation of ionic strength of the medium, addition of the reduction product, benzenesulfonamide, and chloride ion had no pronounced effect on the reaction rate. Decrease of dielectric permittivity of the medium by increasing the CH3CN content increased the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated from the Arrhenius plot. The stiochiometry of the reaction was found to be 1:1, and the oxidation product of phenylpropanolamine was identified as benzaldehyde and ethylideneamine. The rate decreased in D2O medium and the normal isotope effect k′ (H2O) / k′ (D2O) is 2.18. Proton inventory studies have been made in H2O ‐ D2O mixtures. Formation and decomposition constant of BAB‐PPA complexes in the reaction scheme have been determined. The conjugate acid, C6H5SO2NHBr is assumed to be the reactive species. The proposed mechanism and the derived rate law are consistent with the observed experimental results.

Highlights

The chemistry of N-metallo-N-aryl halosulfonamides, generally known as organic haloamines is of interest due to their diverse behavior
A little information exists in the literature on BAB reactions[7,8,9,10], with respect to the oxidation kinetics of pharmaceuticals, which may throw some light on the mechanism[11] of the metabolic conversion in biological systems
The present paper reports for the first time the detailed kinetics of oxidation of phenylpropanolamine with BAB in presence of NaOH medium at 308 K

Summary

Introduction

The chemistry of N-metallo-N-aryl halosulfonamides, generally known as organic haloamines is of interest due to their diverse behavior. Reaction mixtures containing varying compositions of BAB and PPA were kept at 308 K in presence of 0.013 mol dm-3 NaOH for 24 h. Plots of log [BAB] versus time were linear (r > 0.997) indicating a first-order dependence of the rate on [BAB]0.

Results

Conclusion