Kinetics and mechanism of ruthenium(III) catalysed oxidation of amino alcohols by N-bromosuccinimide in perchloric acid medium

Abstract

The kinetics of ruthenium(III) catalysed oxidation of aminoalcohols (primary, secondary and tertiary) by N-bromosuccinimide (NBS) have been investigated in perchloric acid medium. A first order dependence of rate in [NBS] in case of primary aminoalcohols and a second order dependence of rate in [NBS] in case of secondary/tertiary aminoalcohols have been observed. The order in [substrate] is zero in the case of primary aminoalcohols. The order reduces from unity at lowest [substrate] to zero at higher concentrations in the case of secondary and tertiary aminoalcohols. Retarding effect of acid on the rate of reaction has also been observed in the case of diethanol and triethanolamine. The rate of reaction is proportional to [Ru(III) and {<em>k' </em>+ <em>k" </em>[Ru(II1)]}in case of primary and secondary/tertiary aminoalcohols respectively (<em>k' </em>and <em>k" </em>are rate constants for uncatalysed and catalysed paths respectively). A suitable mechanism is proposed in each case and discussed.