Micellar effects on aromatic esters hydrolysis

Abstract

The alkaline hydrolysis of two aromatic esters, 2-naphthyl acetate (2NA) and phenyl acetate (PhA) has been tackled in this work. The reaction has been followed in water and in the presence of cationic surfactants with different chain lengths: dodecyltrimethylammonium bromide (DTABr), tetradecyltrimethylammonium bromide (TTABr), and hexadecyltrimethylammonium bromide (CTABr) and the corresponding hydroxides (DTAOH, TTAOH and CTAOH) at 25. °C. The pseudo-first order rate constants increase with surfactant concentration in the presence of surfactants with reactive counter-ions, while a maximum is reached for bromide surfactants with a constant concentration of hydroxyl ion. Both, the association equilibrium constants of 2NA and PhA with micelles and the rate constant in this medium were determined. The degree of counter-ion association to micelles was considered as a variable parameter, using the adsorption equilibrium of bromide and hydroxide ions to the micelle.