Basic Hydrolysis of Crystal Violet in β-Cyclodextrin/Surfactant Mixed Systems

The basic hydrolysis of crystal violet (CV) in mixed systems consisting of β-cyclodextrin (β-CD) and a micelle-forming surfactant, cetyltrimethylammonium chloride (CTACl), has been studied. β-CD was found to catalyze the basic hydrolysis of CV through the interaction of its hydroxyl group, in its deprotonated form, with the carbocation in the complexed substrate. The addition of small amounts of CTACl, with [CTACl] below the critical micelle concentration, to β-CD solutions does not have an effect upon the observed rate constant for the basic hydrolysis of CV. This behavior is different from that observed for the alkaline hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide and nitrophenyl acetates in mixed β-CD/cationic surfactant systems. The proposed mechanism allows us to explain the experimental results on the basis of the high percentage of uncomplexed β-CD in equilibrium with the micellar system, the low CV concentration, and the high value for the binding constant of CV by β-CD.