Kinetics of the interaction of ninhydrin with the [Ni(II)-histidine]+ complex in water and surfactant micelles

Kinetics of the condensation reaction of ninhydrin and the [Ni(II)-histidine]+ complex has been studied spectrophotometrically at pH 5.0, both in aqueous and aqueous-cationic micelles of cetyltrimethylammonium bromide (CTAB). The same product was obtained in both the media. The results obtained in the micellar medium are treated quantitatively in terms of the kinetic pseudo-phase and Piszkiewicz models. The rate constants, binding constants with the micelles, and the index of cooperativity have been evaluated. On the basis of observed data a possible mechanism has been proposed. The same product was obtained in nonionic micelles of TX-100, but the studies were hampered due to the appearance of turbidity, whereas anionic micelles of sodium dodecyl sulphate did not catalyze the reaction.