Micellar rate effects in the alkaline fading of crystal violet in the presence of various surfactants

Abstract

Abstract The influence of surfactants of various types (nonionic, cationic, anionic, and zwitterionic) on the rate of reaction of the crystal violet, cationic triphenylmethane dye, with the hydroxide ion in unbuffered aqueous solutions was studied using the spectrophotometric method. It was found that the values of the rate constants increase in the presence of the cationic, nonionic and zwitterionic surfactants, and decrease on the addition of the anionic surfactant at concentrations both below and above the CMC. The variation of the rate constants along with the change in the concentration of the surfactants may be explained on the basis of conception about distribution of the reagents between aqueous and micellar phases and the changing of their properties depending on local microenvironment. The character of the salt effects upon the rate constants was explained. It was revealed, that the Piszkiewicz's model of micellar catalysis is inapplicable even semi-quantitatively to the most of the examined systems.