Ag(I) catalyzed oxidation of hypoxanthine and xanthine by Mn (VII) in aqueous Bronsted acid solutions: A kinetic and mechanistic study

Abstract

Mn (VII) is a widely used as an oxidizing agent, but it could not oxidize hypoxanthine (HXAN), and xanthine (XAN) even in concentrated aqueous Bronsted acid (HClO4, H2SO4) media, and at elevated temperatures. However, in the presence of an Ag(I) or AgNO3 catalyst, aqueous Bronsted acid medium, and Mn (VII), the oxidation of Xanthine and Hypoxanthine transpired smoothly. It was discovered that under catalytic circumstances, at constant acidity and temperature, both [(Mn (VII)] and [Xanthine / Hypoxanthine Alkaloid] reactions obeyed basic I - order kinetics. It was further noted that at constant acidity and temperature, increase in [Ag(I)] accelerated the reactions significantly. Rate acceleration observed in oxidation of Xanthine and Hypoxanthine using Mn (VII) at constant [Ag(I)], constant temperature was attributed to increase in concentration of aqueous Bronsted acid (HClO4, H2SO4). The acidity functions established by Bunnett-Olsen Zucker-Hammett, and Bunnett were used for analyzing rate enhancements in this present work. The observed Bunnett-Olsen criteria of acidity functions suggesting the involvement of H2O molecule as H+(proton) transferring agent in the slow step of most plausible mechanism proposed.