QUATERNARY HETEROARENIUM ALDOXIMES AS CATALYSTS FOR CLEAVAGE OF PHOSPHATE-ESTERS

1-Methyl-(Ia - Id) and 1-dodecyl-2-, 3- and 4-hydroxyiminomethylpyridi nium salts (Ie - Ih), as well as 1-methyl- (IIa) and 1-dodecyl-3-hydro xyiminomethylpyridazinium salts (IIb, IIc), were synthesized as cataly sts for hydrolytic cleavage of organophosphates. The activities of the prepared catalysts were evaluated by measuring rate constants of hydr olysis of 4-nitrophenyl diphenyl phosphate (PNPDPP) under conditions o f a pseudo-first-order reaction. The observed reactivity of pyridinium aldoximes Ia - Ih towards PNPDPP in neutral or slightly basic aqueous solutions (pH 7.2 and 7.8) depends on the acidity of the hydroxyimino group. The cleavage of PNPDPP is strongly accelerated in solutions of 1-dodecylhydroxyiminomethylpyridinium salts Ie - Ih above their criti cal micellar concentration (CMC). Considerable effect on the velocity of PNPDPP cleavage was observed when quaternary pyridinium aldoximes I e - Ih were comicellized with inert cationic tenside hexadecyltrimethy lammonium bromide (CTAB). 1-Dodecyl-3-hydroxyiminomethylpyridazinium s alts IIb and IIc were unstable in aqueous solutions under the above-me ntioned conditions.