Esterolysis in cyclodextrin–polyelectrolyte systems

Abstract

The hydrolyses of m-nitrophenyl acetate (MNPA) and p-nitrophenyl indol-3-ylacetate (PNPIA) in the presence of α- or β-cyclodextrin and polyelectrolytes or surfactans have been carried out. The acceleration and deceleration effects of the added electrolytes on the acylation and deacylation reaction have been investigated. The polyelectrotytes examined were poly-(4-vinyl-N-ethylpyridinium bromide), poly-(4-vinyl-N-n-butylpyridinium bromide), poly-(4-vinyl-N-benzylpyridinium chloride)(BzPVP), the copolymer of 4-vinyl-N-hexadecytpyridinium bromide (5%) and 4-vinyl-N-benzylpyridinium chloride (95%)(Cl₁₆BzPVP), diallyldiethylammonium chloride–sulphur dioxide copolymer. poly-L-lysine, sodium polyethylenesulphonate and sodium polystyrenesulphonate. The surfactants were hexadecyltrimethyl-ammonium bromide, sodium dodecyl sulphate, and poly(oxyethylene) dodecyl ether. The acylation step of MNPA with cyclodextrin was inhibited by cationic and hydrophobic polyelectrolytes such as C₁₆BzPVP, and surfactants; this was attributed to the adduct formation between the additives and cyclodextrin. (The dissociation constants were estimated from kinetic data.) In contrast, the acylation and deacylation steps of PNPIA with cyclodextrin were accelerated by the addition of both cationic arid hydrophobic polyelectrolytes (e.g. C₁₆BzPVP and BzPVP); this was ascribed to the accumulation effect of PNIPA and cyclodextrin around the polyelectrolyte.