Catalytic Activity of Ruthenium(III) on the Oxidation of an Anticholinergic Drug-Atropine Sulfate Monohydrate by Copper(III) Periodate Complex in Aqueous Alkaline Medium - Decarboxylation and Free Radical Mechanism

摘要

Atropine sulfate monohydrate (ASM) is an anticholinergic drug, having a wide spectrum of activity. Hence, the kinetics of oxidation of ASM by diperiodatocupcrate (DPC) in the presence of micro (10~(-6)) amounts of Ru(III) catalyst has been investigated spectrophotometrically in aqueous alkaline medium at / = 0.50 mol dm~(-3). The reaction between DPC and ASM exhibits 1:2 stoichiometry (ASM:DPC) i. e., one mole of ASM require two moles of DPC to give products. The main oxidation products were confirmed by spectral studies. The reaction is first order with respect to [DPC] and [Ru(III)], while the order with respect to [ASM] and [OH ] was less than unity. The rates decreased with increase in periodate concentration. The reaction rates revealed that Ru(III) catalyzed reaction was about seven-fold faster than the uncatalyzed reaction. The catalytic constant (K_c) was also determined at different temperatures. A plausible mechanism is proposed. The activation parameters with respect to slow step of the mechanism were calculated and the thermodynamic quantities were also determined. Kinetic experiments suggest that [Cu(H2IO6)(H2O)2] is the reactive Cu(III) species and [Ru(H2O)5OH]~(2+) is the reactive Ru(III) species.