Oxidative Degradation of Atropine Drug by Permanganate Ion in Perchloric and Sulfuric Acid Solutions: A Comparative Kinetic Study

摘要

The kinetics of oxidations of atropine (ATR) by permanganate ion in both perchloric and sulfuric acid solutions was studied using spectrophotometric technique at a constant ionic strength of 1.2 moldm-3 and at 25°C. In both acids, the reactions showed a first order dependence with respect to [permanganate], whereas the orders with respect to [ATR] and [H+] were found to be less than unity. The effect of acid concentration suggests that the reactions were acid-catalyzed. Variation of either ionic strength or dielectric constant of the medium had no effect significantly on the oxidation rates. The reactions mechanism adequately describing the kinetic results was proposed. In both acids, the main oxidation products of atropine were identified by spectral and chemical analyses as tropine and phenylmalonic acid. Under comparable experimental conditions, the oxidation rate of atropine in sulfuric acid was approximately three times higher than that in perchloric acid. The reactions constants involved in the different steps of the reactions mechanism have been evaluated. With admiration to the rate-limiting step of these reactions, the activation parameters have been evaluated and discussed.