Kinetic study for the oxidation of amino acids Schiff-base using permanganate ion

الملخص

In the present investigation the kinetics study of amino acids Schiff-base
oxidation by permanganate ion have been studied at different pH (ranged between6-8)
and different temperatures (ranged between 278.16- 298.16Ko). The Schiff-bases were
prepared from the condensation between amino acids (glycine, alanine, valine ,
leucine, phenyl alanine , serine and aspartic acid), and salicyldehyde. The rate were
studied under pseudo order condition with an excess in the concentration of schiffbase
10 times over the oxidant. The kinetics were followed by monitoring the
disappearance of permanganate ion spectrophotometrically at two wavelength 418 and
526 nm , respectively. The results showed that the observed rate is second- order in
oxidant concentration , first- order in Schiff- base concentration and inverse-order in
hydrogen ion concentration. In all studied cases no auto catalytic effect has been
observed. The variation of the ionic strength of reaction medium have no significant
effect on the reaction rate. This observation suggested that in the rate-determiningstep
one or more of the reactants are neutral molecule. The effect of temperature on
the rate constant has been studied and activation parameters were evaluated. The
isokinetic theory was applied for the activation parameters. The results showed
presence of isokinetic temperature and a compensation effect between enthalpy and
entropy of activation which support the idea of one mechanism domination.
Finally the stoicheiometry of the reaction shows that three moles of oxidant
are consumed for each mole of schiff-base and the products contain ammonia, carbon
dioxide and organic acids .