An-Najah Staff

Kinetic oxidation of L-cysteine by [Fe(Fz)2]1- complex was carried out in acidic medium under pseudo rate conditions. The molar ratios between iron(III), iron(II) and Ferrozine (HFz) complexes in absence and presence of L-cysteine were individually determined using job's method. The formation of [Fe2+-Fz] at lmax = 562nm was spectrophotometrically followed during this kinetic study. The reaction is found to be first-order with respect to iron(III) and L-cysteine, second-order with respect to HFz-1 ligand and reversed second-order with respect to hydrogen ion concentrations. The salts effect was determined and no radical species have been detected. The kobs rose when the temperature was increased which empowered the activation parameters of the rate-determining step calculations. A reaction mechanism and rate law derivation are proposed with a pre-equilibrium of an adduct formation between L-cysteine and [Fe3+-Fz] complex.