Studies in kinetics and mechanism of oxidation of d-glucose and d-fructose by alkaline solution of potassium iodate in the presence of Ru(III) as homogeneous catalyst

Kinetics of oxidation of d-glucose (glc) and d-fructose (fru) by potassium iodate has been studied for the first time in alkaline medium using Ru(III) as homogeneous catalyst. The linear dependence of the reaction rate at lower [IO3−] and [OH−] tends towards zero-order at their higher concentrations. Experimental results also show that the order with respect to [Ru(III)] is unity and the order with respect to [reducing sugar] is zero in the oxidation of both glc and fru. Variation in [Cl−] and ionic strength (μ) of the medium does not affect the oxidation rate. The species, [RuCl2(H2O)2(OH)2]− and IO3−, were found to be the reactive species of Ru(III) chloride and potassium iodate in alkaline medium, respectively. The reactions have also been studied at four different temperatures and with the help of observed values of pseudo-first-order rate constant (k1), the entropy of activation and other activation parameters have been calculated. A common mechanism, where the rate determining step involves the interaction between reactive species of Ru(III) chloride and reactive species of potassium iodate resulting in the formation of an activated complex,Figure optionsDownload full-size imageDownload as PowerPoint slidehas been proposed. The formation of activated complex is very well supported by the spectrophotometric evidence, observed kinetic data and also by the negative entropy of activation observed for the oxidation of both glc and fru. Arabinonic acid and formic acid were identified as the main oxidation products of the reactions.

Graphical abstractKinetics of oxidation of d-glucose and d-fructose by alkaline solution of potassium iodate in the presence of Ru(III) as homogeneous catalyst have been studied. Observed kinetic data with spectrophotometric evidence led us to propose that there is a formation of most reactive activated complex, , in the rate determining step by the interaction of two different species, i.e. [RuCl2(H2O)2(OH)2]− and IO3−.Figure optionsDownload full-size imageDownload as PowerPoint slide