The kinetics of the decolorization reactions of triphenylmethane dyes (BG, MG and PRH) with the cyanide ion (nucleophile) were studied in the presence of anionic micelles of sodium dodecyl sulfate (SDS). The reactions follow pseudo-first order kinetics. The rate constant depends on surfactant concentration. SDS micelles inhibit the overall rate of the reaction between the dye carbocation with the nucleophile. Quantitative analysis of the micellar data obtained has been done by applying a positive cooperativity model of enzyme catalysis. For all the dyes under study, the value of n (index of cooperativity) has been found to be greater than one. The inhibitory effect has been explained in terms of hydrophobic and electrostatic interactions of various species present in the reaction systems.
Bunton, CA, Nome, F, Quina, FH, Romsted, LS (1991) Acc Chem Res24:357.