Kinetic Study of Oxidation of Three Simple Sugars by Peroxydisulphate

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Ali, Ismat Hassan
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The present work deals with a systematic kinetic study of the redox reactions of three simple sugars, fructose, galactose and mannose with peroxydisulphate under uncatalyzed conditions over a temperature range 60–80o C and in the presence of Ag(I) as a catalyst over a temperature range 35 – 500 C. Two aspects of the study were involved: a) Kinetic study. b) Products analysis. The method of iodometry was used to follow the progress of the reactions at different time intervals. A systematic kinetic study of the uncatalyzed redox reactions showed that such reactions are first order in peroxydisulphate concentration and fractional order of 0.2 in simple sugars concentrations. The study on the Ag(I) catalyzed reaction revealed that the reaction is first order with respect to Ag(I) and peroxydisulphate but zero order with respect to the simple sugars. The thermodynamic parameters; activation energy (Ea), frequency factor (A), entropy of activation ( ) and free energy change of activation ( ) of both uncatalyzed and Ag(I) catalyzed redox reactions were calculated by using the values of rate constants obtained at different temperatures. The rate laws for the reactions were determined and mechanisms were suggested to explain the experimental results. The analysis of the reaction products revealed the presence of formaldehyde and formic acid in the volatile fractions in all reactions. The presence of these products was confirmed by spot tests
Kinetic,Study,Oxidation,Simple Sugars, Peroxydisulphate