Effect of gemini (alkanediyl-α,ω-bis(dimethylcetylammonium bromide)) (16-s-16, s=4, 5, 6) surfactants on the interaction of ninhydrin with chromium-glycylphenylalanine

The effect of gemini (alkanediyl-alpha,omega-bis(dimethylcetylammonium bromide)) (16-s-16, s = 4, 5, 6) surfactants on the interaction of ninhydrin with chromium(III) complex of glycylphenylalanine ([aCr(III)-Gly-Phe](2+)) has been investigated using UV-visible spectrophotometer at different temperatures. The order of reaction with respect to [Cr(III)-Gly-Phe](2+) is unity while it is fractional with respect to ninhydrin. Whereas, the values of rate constant (k(psi)) increase and leveling-off regions, like conventional single chain cetyltrimethylammonium bromide (CTAB) surfactant, were observed with geminis, later produces a third region of increasing it* at higher gemini surfactant concentrations. This unusual third-region effect of the gemini micelles is assigned to changes in their micellar morphologies. The results obtained in micellar media were treated in terms of pseudo-phase model. The values of thermodynamic parameters (Ea, Delta H-# and Delta S-#) and binding constants (K-A and K-Nin) have been evaluated. (C) 2014 Elsevier B.V. All rights reserved.