COMPARATIVE STUDY OF RUTHENIUM(III)-CATALYSED OXIDATION OF D(+) XYLOSE BOTH IN ACIDIC AND ALKALINE MEDIA

摘要

Kinetic investigation on ruthenium(III)-catalysed oxidation of xylose by a solution of potassium bromate in the presence of mercuric acetate as a scavenger for Br~- ion has been carried out in the temperature range 30-45°C both in acidic and alkaline media. First order kinetics in the lower KBrO3 concentration range tended to zero order at higher concentration was observed in acidic medium, but the reaction shows first order dependence in alkaline medium. The order of reaction with respect to substrate is zero, but the order with respect to Ru(III) is one both in alkaline and acidic medium. Increase in [Cl~-] shows negligible effect while increase in [H~+] shows negative effect in acidic medium. In alkaline medium increase in [Cl~-] shows positive effect whereas increase in [OH'] shows negative effect. Negligible effect of mercuric acetate and ionic strength of the medium was observed in both media. D2O has an insignificant effect on the reaction rate. A suitable mechanism in conformity with the kinetic observations has been proposed both in alkaline and acidic media and intermediates have been studied for confirmation.