Catalytic activity of Rhodium (III) on oxidation of some alpha-amino-acids by Ceric (IV) in aqueous perchloric acid medium - a kinetic and mechanistic approach

摘要

The kinetics of the Rh(III) catalysed oxidation of alanine and valine with Ce(IV) has been studied in perchloric acid medium at different temperatures (25 deg C-40 deg C) under the conditions [amino-acid]_T [Ce(IV)][Rh(III)]_T in 1.0 mol dm~(-3) perchloric acid media.Analysis of the results shows the observed rates of oxidation indicate zero order in [oxidant] and first order dependence on amino acids viz,alanine,valine] respectively.The reaction exhibits first order dependence on Rh(III) and fractional order dependence on the concentration of medium (i.e.HClO_4).Variation of ionic strength by adding NaClO_4 have no significant effect on the reaction rate.The observation shows that the rate determining step proceeds through an ion-dipole type interaction.A plausible rate law can be proposed as where AA = amino acids viz.alanine,valine and k' is second order rate constant.