Studies on the Kinetics and Mechanism of Drug Degradation. I. : Kinetics and Mechanism of Degradation of Chlorphenesin Carbamate in Strongly Alkaline Aqueous Solutions

The kinetics and mechanism of the degradation of chlorphenesin carbamate (α-CPC) in strongly alkaline aqueous solutions were studied at 0 to 20°C. The degradation did not obey pseudo-first order kinetics, but was shoun to involve a complex reaction accompanied by consecutive, parallel and reverse reactions. The rate law of degradation could be approximated in terms of specific base-catalyzed hydrolysis, that is k=kOH αOH, from the rate constant-pH profile. The Arrhenius plots of the degradation were approximately linear. Chlorphenesin-2-carbamate (β-CPC) and chlorphenesin (CP) were detected as alkaline degradation products of α-CPC.The mechanism proposed for the degradation of α-CPC involves migration of the carbamoyl group to the adjacent OH group and removal of the carbamoyl group in the presence of hydroxide ions.