TEMPLATE MECHANISM FOR THE INTERACTION OF NINHYDRIN WITH CADMIUM(II) AND COPPER(II) COMPLEXES OF L-ASPARTIC ACID - A KINETIC-STUDY

Kinetic studies of ninhydrin reaction with cadmium(II) and copper(II) complexes of L-aspartic acid have been made spectrophotometrically as a function of [ninhydrin], [acetate ion] and temperature at pH 5.0. The reaction follows a pseudo-first order kinetics with respect to the aspartic acid complexes in the presence of excess of [ninhydrin] and fractional order kinetics with respect to ninhydrin. The reaction proceeds through the formation of a new chelate ring which is the essential feature of template mechanism (CLAM reaction). Copper(II) and cadmium(II) retard the cleavage of alpha-COOH group of aspartic acid. The condensation of coordinated amino group to coordinated carbonyl group occurs within the coordination sphere of metal ion. On the basis of the observed data, template mechanisms have been proposed.