Abstract

MECHANISTIC INVESTIGATIONS OF UNCATALYSED AND RUTHENIUM(III) CATALYSED OXIDATION OF PHARMACEUTICALLY IMPORTANT D-SORBITOL BY PERIODATE IN AQUEOUS ALKALINE MEDIUM

Sharanappa Totappa Nandibewoor* and Prashant Ashok Magdum

ABSTRACT

The kinetics of oxidation of pharmaceutically important D-Sorbitol (DSorb) by periodate both in the absence and presence of ruthenium(III) catalyst in alkaline medium at 298 K and at a constant ionic strength of 0.21 mol dm-3 was studied. The reaction exhibits 1:1 stoichiometry ([D-Sorb]: [periodate]). The reaction shows first order kinetics in [periodate], [Ru(III)] and less than unit order both in [D-Sorb] and [OH-]. The ionic strength and dielectic constant of the medium did not affect the rate significantly. The main products were identified by spot tests, FT-IR and LC-MS spectral studies. Based on the experimental results, the possible mechanisms were proposed. The reaction constants involved in the different steps of the mechanisms were evaluated. The catalytic constant (Kc) was also calculated for Ru(III) catalysis at different temperatures. The activation parameters with respect to the catalyst and slow step of the mechanisms were computed and also thermodynamic quantities determined. Kinetic studies suggest that the active species of periodate and Ru(III) were found to be [H2IO6 3-] and [Ru(H2O)5OH]2+ respectively.

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