Complexation of nickel-, cobalt- and copper(II) with L-3,4-dihydroxyphenylalanine - Kinetic studies

Kinetic study on the interaction of Ni-II, Co-II and Cu-II with L-3,4-dihyd roxyphenylalanine (L-dopa) has been carried out under first order condition as a function of pH and temperature at I = 0.1 M (KNO3). A reaction scheme consistent with the results that at pK 8.64 both amino and hydroxyl groups undergo deprotonation, has been proposed. The overall rate constants have been resolved into stepwise rate constants. The activation parameters corre sponding to stepwise rate constants, to support the proposed mechanism, hav e been evaluated. The suggested mechanism has been further confirmed by the calculation of water exchange rate constant.