Hydrolysis of 2,4-Dinitrophenyl Phosphate Catalyzed by Single-Chain, Twin-Tailedand Bolaform Surfactants

摘要

Cationic micelles catalyze hydrolysis of dianionic 2,4-dinitrophenyl phosphate,(2,4-DNPP2-) and of monoanionic 2,4-dinitrophenyl sulfate. Tri-n-octylalkylammonium ions do not form micelles in water, but they speed hydrolysis of 2,4-DNPP, probably because of interactions between it and clusters of the ammonium ion. In these reactions, first-order rate constants increase on addition of surfactant or hydrophobic ammonium ion, and become constant when the substrate is fully bound to micelles or similar assembles. Colloidal assemblies of single-chain and twin-tailed surfactants and hydrophobic ammonium ions have very different gross structures, but for both the ionic-head groups are in contact with water and associated counter-ions. (jes)