Comparative study on Pd(II) and Ru(III) catalyzed oxidation of alpha-amino-beta-hydroxypropionic acid (dl-serine) by acid bromate: A kinetic study

Comparative study on Pd(II) and Ru(III) catalyzed oxidation of dl-serine and dl-threonine by acidic solution of potassium bromate in the presence of mercuric acetate, as a scavenger have been made in the temperature range of 30 degrees-45 degrees C. In case of both catalyst rate shows zero order kinetics in bromate [BrO3- >] and order of reaction is one with respect to substrate and Pd(II) and Ru(III) respectively. Increase in [Cl-] showed positive effect, while [H+] showed zero effect. Negligible effect of mercuric acetate and ionic strength of the medium was observed. A transient complex, formed between [PdCl2] and amino acid. [PdCl2] being reactive species of Palladium(II) chloride in 1:1 ratio, disproportionates in a slow and rate determining step while in case of Ru(III) a transient complex, formed between [RuCl6](3-) and amino acid. ([RuCl6](3-) being reactive species of ruthenium (III) chloride) in 1:1 ratio, disproportionates in a slow and rate determining step various activation parameters have been calculated. A suitable mechanism in agreement with observed kinetics has been proposed.