Influence of Cationic Cetyltrimethylammonium Bromide on Rate of Zn(II)-Histidine Complex and Ninhydrin

Abstract

Paper analyses the influence of cationic cetyltrimethylammonium bromide on rate of Zn(II)-histidine and ninhydrin. UV-visible spectroscopy was applied to note absorbance of Zn(II)-histidine complex with ninhydrin at the end of reaction in the two systems. Rate constant, k_obs, (in aqueous) and rate constant, k_ψ, (in cetyltrimethylammonium bromide, CTAB) were determined by computer software. Reactions depict first-order in Zn(II)-histidine concentration and fractional-order in ninhydrin concentration in aqueous and micellar media. The results achieved indicate that the reactions take place principally by the same reaction mechanism in both the media. Critical micelle concentration of CTAB surfactant was calculated by recording the conductivity as a function of surfactant concentrations. Influence of various amounts of surfactant on Zn(II)-histidine complex and ninhydrin reaction was performed under different reaction conditions. Reaction was catalyzed and accelerated efficiently by surfactant medium compared to aqueous medium. The observed influence of surfactant on rate has been mentioned in details and their quantitative treatment of kinetic results have been deduced by the means of Menger and Portnoy model for micellar catalysis.