Hydrolysis of 2,4‐dinitrophenyl phosphate catalyzed by single‐chain, twin‐tailed and bolaform surfactants

Abstract

Abstract The spontaneous hydrolysis of 2,4‐dinitrophenyl phosphate dianion (2,4‐DNPP) is speeded by cationic micelles of cetyltrimethylammonium salts [CTAX, X = Cl, Br, (SO 4 ) 0.5 ] and of bolaform(22)X 2 [Me 3 N + (CH 2 ) n N + Me 3 2X − , n = 22, X = Br, (SO 4 ) 0.5 ]. The shorter‐chain bolaform surfactants ( n = 16, 12, X = Br) are less effective. Twin‐chain surfactants of didodecyl and dicetyldimethylammonium salts (C 12 H 25 ) 2 NMe 2 X, X = Br, Cl, (SO 4 ) 0.5 and (C 16 H 33 ) 2 NMe 2 X, X = Cl, (SO 4 ) 0.5 and pyridinium‐ion surfactants C 16 H 33 NC 5 H 5 Cl and its 4‐(dimethylamino) derivative, also speed hydrolysis. The first‐order rate constants increase to limiting values ( k ′ M ) when substrate is fully bound and these values are not very sensitive to the nature of the surfactant and are generally greater than in water by factors of 20–110. However, the extent of binding of 2,4‐DNPP is sensitive to the nature of the surfactant. Tertiary amines, e.g. , pyridine and DABCO speed the reaction in CTACl by generating an intermediate phosphoramidate.