Influence of dimeric gemini surfactant micelles on the study of nickel-glycylleucine dipeptide and ninhydrin

Abstract

Influence of dimeric gemini surfactant micelles on the study of nickel-glycylleucine dipeptide ([Ni(II)-Gly-Leu]+) and ninhydrin was carried out in the temperature ranging from 333 K to 353 K. An UV–vis spectrophotometer was employed to record the absorbance of product at definite time intervals. Rate of reaction was strongly catalyzed by the gemini surfactants. In the present reaction, the first-order dependence in metal-dipeptide complex and fractional-order dependence in ninhydrin were observed. For the measurements of critical micelle concentration (CMC), conductivity method was used. Rate constants (k ψ) increase and levelling-off regions are detected with [gemini] (just like conventional monocationic surfactant). Later, gemini produces a third region at higher [gemini] where, fast increment in k ψ is observed. The catalytic role of surfactants has been described below and above the CMC of gemini surfactants. From this study, binding constants of reactants and thermodynamic parameters have been evaluated. The kinetic results and observed catalysis could plausibly be rationalized by Menger and Portnoy’s pseudo-phase model of micellar catalysis.