Synthesis and Characterization of Dicationic Gemini Surfactant Micelles and their Effect on the Rate of Ninhydrin-Copper-Peptide Complex Reaction

Herein, we have synthesized and characterized dicationic Gemini surfactants. The effect of their micelles on the rate constant of ninhydrin with [Cu(II)-Gly-Gly](+) complex reaction was investigated under pseudo-first-order-conditions. Experiments were carried out by means of spectrophotometry. First- and fractional order dependencies on [Cu(II)-Gly-Gly](+) and ninhydrin, respectively, were found. The results indicated that the efficiency of micellar catalysis by Gemini surfactants was significantly higher as compared to single-chained surfactant cetyltrimethylammonium bromide, CTAB. The Gemini surfactant produces a catalytic effect and leveling-off regions (just like CTAB) on the reaction rate. Later, Gemini with higher concentrations gives a third region of increasing k(psi). The effect of surfactants was rationalized by hydrophobic and electrostatic interactions. The observed kinetic effects are explained by applying the Menger-Portnoy model.