Hiroshige Yano

Cationic micellar effects on the kinetics of the protolysis of carboxylic acids

Abstract The kinetics of the protolysis of aromatic carboxylic acids solubilized in a micelle of dodecylpyridinium chloride has been studied by the ultrasonic relaxation absorption measurements. The rate constants are dependent on the acid dissociation constant K a and the results are interpreted by means of the Bronsted catalysis law. The micellar catalytic effect is discussed in comparison to those in the acid and base equilibria of carboxylic acids and amines in the micellar solutions. The volume change of the reaction is also found to be dependent on K a .

Micellar effect on the kinetics of the base equilibrium of amino acids studied by the ultrasonic absorption method

Ultrasonic relaxation absorption has been measured in aqueous solutions of amino acids (tryptophan, leucine, glycine, phenylalanine, asparagine) in the absence and in the presence of micelles of sodium dodecylsulphate. The relaxation absorption was ascribed to the base equilibrium of amino acids, and the rate constants, the base dissociation constant, and the volume change of the reaction were obtained. The smaller micellar catalytic effect for the base equilibrium of amino acids, compared to those of amines and ammonia was ascribed to the electrostatic effect of the carboxylate group. The reaction mechanism, including the interactions of amino acid and the SDS micelles, were discussed.