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

Abstract

The basic hydrolysis of crystal violet (CV) in mixed systems consisting of beta-cyclodextrin (beta-CD) and a micelle-forming surfactant, cetyltrimethylammonium chloride (CTACl), has been studied. beta-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 beta-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 beta-CD/cationic surfactant systems. The proposed mechanism allows us to explain the experimental results on the basis of the high percentage of uncomplexed beta-CD in equilibrium with the micellar system, the low CV concentration, and the high value for the binding constant of CV by beta-CD.

The formation of host–guest complexes between surfactants and cyclodextrins

“…The formation of host-guest complexes influences the kinetics of different reactions [28]. When the reaction rate decreases due to the presence of CDs, these can be used as stabilisers; however, of more interest are the situations in which CDs accelerate reactions or may even participate directly in guest hydrolysis [185,186].…”

“…Garcia-Rio and coworkers have developed models that allow the computation of stability constants for CD-S host-guest association by measuring the rate constants of solvolysis of chemical probes, such as, crystal violet [28], 4-methoxybenzenesulfonil chloride [192], benzoyl chlorides [193], Nnitrososulfonamide [194] and m-nitrophenyl acetate [195].…”

Influence of colloid suspensions of humic acids on the alkaline hydrolysis of N‐methyl‐N‐nitroso‐p‐toluene sulfonamide

“…The insert of Fig. 5 presents the values of the binding constants of MNTS [28,37,[39][40][41] and CV [42,52] for different normal micelles as a function of the chain length of the surfactant. Taking into account these ratios, and assuming that the binding constant of CV [15] for OTACl and 45 times bigger than the ratio of SDS.…”

Permethylated-β-Cyclodextrin Capped CdTe Quantum Dot and its Sensitive Fluorescence Analysis of Malachite Green

“…When the added amounts of QDs were higher than this concentration, the value of ΔF began to decrease. From the reported experimental data with HNMR and theoretical calculation results [26,27], one crystal violet molecule, which has very similar chemical structure to MG, was introduced into one β-CD molecule through its wide opening and one complete phenyl group was accommodated within its interior, the stoichiometry of the complex is 1:1. Our study in the present work also confirmed that the stoichiometry of the complex β-CD-MG is 1:1.…”