An-Najah Staff

The kinetics oxidation of L-cysteine by 3-di-2-pyridylketone-2-thiophenylhydrazone-iron(III)[Fe(DPKTH)2]3+complex in acidic medium was studied spectrophotometrically at 36Co temperature.The differential rate method (initial rate) was served in this investigation. The molar ratios of DPKTH to iron(III) and iron(II) individually, were found to be [2:1] [DPKTH :iron(III)/(II)]. The reaction was stroked to be first-order with respect to iron(III) and L-cysteine,second-order with respected to DPKTH ligand and reversed second-order with respected tohydrogen ion concentration. Added salts did not affect the rate and no free radical was detectedwhen radical detector was placed in the reaction mixture. Ethanol solvent ratio was found to effect both the initial rate and the maximum absorbance (λmax) of [Fe(DPKTH)2]2+complex. The initial raterose when the temperature was increased which empowered the activation parameters calculations.From the evaluation of the obtained linear data, a reaction mechanism is proposed which involves a pre-equilibrium of an adduct formation between L-cysteine and [Fe(DPKTH)2]3+complex.