A kinetic Study of the Oxidation of two Simple Sugars by Peroxydisulphate

Abstract

The present work deals with a kinetic study of redox reactions of two simple sugars (Glucose and Maltose) with peroxydisulphate ion under uncatalysed conditions over the temperature range (60ْ – 80 ْC). It was found that these reactions follow consecutive two main paths: Thermal decomposition of peroxydisulphate. Bimolecular reactions of these sugars with peroxydisulphate. Two aspects of the study were involved: Kinetic study. Products analysis. The progress of these reactions was followed by examining the concentration of peroxydisulphate iodometrically at different times. The study showed that the reaction rate follows a first order in peroxydisulphate and a fractional order of (0.25) in the simple sugars concentrations. Thermodynamic parameters, activation energy, frequency factor, entropy change and free energy change of the redox reactions were calculated from rate constants obtained at different temperatures. The rate laws of the reactions were determined and free radical mechanisms were proposed. The analysis of the reaction products revealed the presence of formaldhyde and formic acid in the volatile fraction as main products and these were confirmed by spot tests. The amounts of formaldhyde were determined spectro-photometrically and those of formic acid were determined titrimetrically