Abstract
Kinetics and mechanism of oxidation of diethanolamine (DEA) and triethanolamine (TEA) by potassium bromate in presence of ruthenium(III) chloride as homogeneous catalyst in perchloric acid medium have been investigated. First order kinetics with respect to each of [KBrO3] and [Ru(III) chloride] was observed in the oxidation of both DEA and TEA. With about eight-fold variation in [DEA] and 10-fold variation in [TEA], first order kinetics in [substrate] was observed up to nearly 3-fold variation in [DEA] and 5-fold variation in [TEA]. Kinetics with negative effect of [substrate] became more complex in both cases when a significant decrease in pseudo first order rate constant was observed at their higher concentrations. Inverse fractional order in [H+] was noted throughout its 10-fold variation. Variation in [Hg(OAc)2], [Cl–] and ionic strength (μ) of the medium did not bring about any significant change on the rate of reaction. The values of rate constants observed at four different temperatures were utilised to calculate the activation parameters. Acetic acid and ammonia have been identified as main oxidation products of the reactions. A suitable mechanism involving the formation of a complex between [Ru(III)–aminoalcohol] complex and bromate ion prior to the rate-determining step is proposed.