Abstract
The hydrolysis of p-nitrophenyldiphenyl phosphate (PNPDPP, 7) catalyzed by N-dodecylaminoethanol (6a), N-tetradecylaminoethanol (6b), N-methyl-N-tetradecylaminoethanol (6c), and N-hexadecylaminoethanol (6d) was investigated at 25°C at various pH values in aqueous media containing additives. Added ethanol or dimethoxyethane produces very little activity of 6a, b, c toward 7. The highest activities of 6a, b were found at pH 8.0 and 8.5 in solvents containing 20% glycerol or ethylene glycol. Under no conditions was N-hexadecylaminoethanol (6d) found to be active. The kinetics of the reaction of 6b with 7 were also investigated in a medium containing various amounts of glycerol, polyethylene glycol 400 (PEG 400), and water at pH 7.6-8.5. The best catalytic system comprised 3 mM 6b in 20% aqueous ethylene glycol, pH 8.5, which accelerated the hydrolysis of 7 by 1700-fold over the blank rate. Kinetic experiments conducted using [7]/[6b] = 1 and 2 demonstrate that 6b exhibits true turnover catalysis. A mechanism for the catalyzed reaction is proposed.Key words: ß-aminoethanols, hydrolysis, p-nitrophenyldiphenyl phosphate, micelles, polyhydroxy alcohols.
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