Kinetic study of the reaction of sulfamethoxazole and glucose under acidicconditions - I. Effect of pH and temperature

The kinetics of the reaction of sulfamethoxazole (SMX) in 5% w/v glucose to form the corresponding alpha- and beta-glucosylamines over the pH range of 0.80-6.88 at 37 degrees C has been investigated. The identity of the gluco sylamines was determined by H-1-nuclear magnetic resonance spectroscopy of an authentic sample of the alpha-glucosylamine (USP) and the reaction produ cts, and by interconversion of this compound to the corresponding beta-anom er. The reaction followed pseudo first-order reversible kinetics and involv ed specific acid and general acid-base catalysis. The pH-rate profile demon strated that over the pH range of 0.80-2.90 and 5.50-6.88 the reactions wer e dependent on H+ concentration but pH independent between pH 3.00-5.45, wh ich reflects the influence of ionization of SMX and the glucosylamines on t he reversible reaction. Interpretation of the data with respect to kinetic models and rate equations for the formation and hydrolysis of the glucosyla mines was investigated. Temperature dependence studies followed the Arrheni us equation with an Ea of 49.28 kJ mol(-1) for the forward and 63.46 kJ mol (-1) for the reverse reaction at pH 2.89 respectively. (C) 2000 Published b y Elsevier Science B.V. All rights reserved.