Ruthenium (VIII) mediated oxidation of some aliphatic and alicyclic ketones by periodate-ruthenium (III) system in aqueous HClO4 medium

Abstract

The kinetics of Ruthenium(III) chloride mediated oxidation of acetone, 2-butanone, 4-methyl-2-pentanone, 2-pentanone, cyclopentanone, and cyclohexanone by sodium periodate in aqueous HClO4 media was zero-order in [IO4−] and first-order in [ketone]. The reaction was independent of added [Ru(III)] and showed first-order dependence on [H+] for all the ketones studied, except acetone. In the case of acetone at [H+] < 0.05 M, the rate was independent of [H+], the order in [Ru(III)] being unity; but at [H+] > 0.05 M the reaction showed unit dependence on [H+] and the order in [Ru(III)] was zero. Ruthenium(VIII) generated in situ is postulated as the hydride abstracting species. A mechanism involving enolization as the rate determining step is proposed. Acetone at lower acidity of the medium is shown to react directly with Ru(VIII). In the absence of ruthenium(III) chloride, the kinetics were first-order in [IO4−], [ketone], and [H+]. Structure-reactivity relationship is discussed and thermodynamic parameters are reported. © 1996 John Wiley & Sons, Inc.