Influence of dicationic quaternary ammonium gemini surfactant system on metal-amino acid complex-ninhydrin reaction

In the current study, we have elucidated the influence of dicationic quaternary ammonium geminis system on metal-amino acid [Ni(II)-his](+) complex-ninhydrin reaction with the help of UV-vis spectrophometer at 343 K and pH 5.0. Under varying experimental conditions, rate constant values, k(psi), were determined using a computerbased program. Quaternary ammonium gemini systems (rate constant values of 16-6-16, 16-5-16 and 16-4-16 at 30 x 10(-5) mol dm(-3) are 5.5 x 10(-5) s(-1), 6.5 x 10(-5) s(-1) and 7.5 x 10(-5) s(-1), respectively) are detected more superior compared to aqueous system (rate constant in aqueous is 1.7 x 10(-5) s(-1)). Study was catalyzed and accelerated by gemini surfactants (even though at concentrations below than their cmc values) compared to aqueous medium. Rate constant increases progressively on increasing [gemini] (region I, where [gemini] is smaller than their cmc) and levelling-off regions attain (region II, at [gemini] up to 400 x 10(-5) mol dm(-3)). Afterward, gemini provides a region III of increasing k(psi) at higher concentration (region III, beyond 400 x 10(-5) mol dm(-3)). Experimental results acquired in dicationic quaternary ammonium gemini surfactant system are deduced quantitatively by kinetic pseudo-phase model. For determination of cmc of geminis having a different methylene spacer chain length (s = 4, 5, 6), the specific conductance at varied [16-6-16], [16-5-16] and [16-4-16] (i.e., water and water + ninhydrin + [Ni(II)-his](+)) were 0.043 x 10 -3 mol dm -3 at 303 K and 0.053 x 10(-3) mol dm(-3) at 343 K; 0.034 x 10(-3) mol dm(-3) at 303 K and 0.044 x 10(-3) mol dm(-3) at 343 K; 0.032 x 10(-3) mol dm(-3) at 303 K; 0.040 x 10(-3) mol dm(-3) at 343 K, respectively, recorded on a conductivity meter. Several activation parameters for 16-6-16, 16-5-16 and 16-4-16 (Delta H-# = 45.0, 43.5 and 42.0 kJ mol(-1); Delta S-# 87.0, 87.6 and 88.3 JK(-1); E-a = 47.8, 46.3 and 44.8 kJ mol(-1)) and binding parameters for 16-6-16, 16-5-16 and 16-4-16 (K-X = 63.0, 58.0 and 54.0 mol(-1) dm(3); K-Y = 70.0, 66.0 and 62.0 mol(-1) dm(3)) are also determined.