INTERACTION BETWEEN PRIMARY ALIPHATIC-AMINES AND CARBOXYLIC-ACID ESTERS IN AQUEOUS MICELLAR SOLUTIONS OF CATIONIC SURFACTANTS

The effects of cetylpyridinium bromide (CPB) on the acid-base equilibr ia of primary aliphatic amines and on the kinetics of reactions of the amines with p-nitrophenyl acetate (PNPA) and p-nitrophenyl caprylate (PNPC) were studied by potentiometric titration and UV spectroscopy. T he values of apparent pK(a) of the amines in the micellar phase, bindi ng constants of their neutral farms, and the surface potentials of mic elles were determined. Cetylpyridinium bromide accelerates the aminoly sis of PNPA by factors of 3 to g by forming mixed micellar aggregates with the amines. The shift of pK(a) values of the amines in micellar s olutions is not the only factor that enhances their reactivity. The su bstrate specificity was found: in contrast to the reaction with PNPA, CPB accelerates (by factors of 15 to 65) or retards (by factors of 4 t o 6) the aminolysis of PNPA depending on the hydrophobicity of the nuc leophilic reagent. The binding constants of substrates, the rate const ants in the micellar phase, and the critical concentrations of micelli zation were determined from the data obtained.