Kinetic study of the formation of triphenylmethanols from cationic triphenylmethane dyes in the presence of nonionic surfactant micelles

The formation rates of triphenylmethanols from corresponding cationic triphenylmethane dyes were investigated in the presence of nonionic surfactant micelles, such as Triton X-100, PONPE-20, Brij-35 and Brij-58. The increases in the formation rates of triphenylmethanols with the hydroxide ion in a nonionic micellar solution were almost comparable to that in the presence of a cationic micelle of stearyltrimetylammonium ion. The increase in the rate was largest with Triton X-100, and the rates with the hydroxide ion increased on the order of about 10(2.0) similar to 10(3.7) fold compared with those in an aqueous solution. The reaction rates for malachite green and brilliant green increased most significantly among the five dyes examined. The rates also increased along with an increase in the hydrophobicity (lipophilicity) balance of the surfactant molecule. These results indicate that the cationic dyes are adsorbed on the hydrophobic core of the surfactant micelle, and that the formed triphenylmethanols are incorporated in the core.