Autocatalysed oxidation of etophylline by permanganate in aqueous sulphuric acid medium- kinetics and mechanistic study

Abstract

The reaction kinetics of oxidation of etophylline by permanganate ions has been investigated in sulphuric acid medium using spectrophotometric techniques at 25°C and at constant ionic strength, 1.60 mol dm-3, under pseudo-first order conditions. An autocatalysis reaction is observed due to the formation of one of the products, MnII. The order with respect to etophylline and MnVII concentrations are found to be unity in each, whereas fractional order with respect to autocatalyst, MnII. As the concentration of acid increases the rate of the reaction increases. The order with respect to acid concentration is less than unity. Based on the experimental results a suitable mechanism is proposed. The influence of temperature on the rate of reaction is studied. The activation parameters and thermodynamic quantities have been determined with respect to slow step of the mechanism. Key words: Autocatalysis, oxidation, etophylline, permanganate.