Okeola O. Fatai, Odebunmi E. O. and Okoye A. Grace
The kinetics of catalytic oxidation of D-glucose and D-galactose by potassium heptaoxodichromate (VI) in alkaline buffer and in the presence of Fe (III) was investigated spectrophotometrically under pseudo-first order condition, temperature of 308K â�?�? 328K and pH of 9.6â�?�?11.0. The reaction was first order with respect to oxidant and sugar concentration. The kinetics data show that the rate of oxidation increased with increase in substrate and oxidant concentration, temperature, ionic strength and pH of the reaction medium. The Arrhenius activation energy and other thermodynamic activation parameters are evaluated. Ea for the unanalyzed reaction of glucose and galactose was 139.8kJmol-1 and 110.0kJmol-1 respectively and 68.8kJmol-1 and 58.5kJmol-1 respectively for catalysed reaction. The activation energy Ea of the reaction with glucose is higher in both catalysed and uncatalysed reaction. The second order rate constant k2 for the catalysed reaction for glucose and galactose is 0.023M-1s-1 an 0.022 M-1s-1 respectively whereas, for the uncatalysed reaction, it was found to be 0.019 M-1s-1 and 0.015 M-1s-1 for glucose and galactose respectively. The positive effect of the catalyst was observed in the oxidation of both sugars.
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