Abstract
Monoperoxyphthalate (MPP) was solubilized in three different aqueous cationic surfactant aggregates composed of (i) a micellar cetyltrimethylammonium chloride (CTACl) solution; (ii) an oil-in-water (O/W) microemulsion (ME) stabilized by CTACl, and a cosurfactant, tert-butyl alcohol, and (iii) a vesicular medium composed of dispersions of dihexadecyldimethylammonium chloride (DHDAC). At pH approximately 8.5 and 25 degrees C, each of these formulations was used to cleave p-nitrophenyl diphenyl phosphate (PNPDPP). The aggregate and the maximum pseudo-first-order rate constants ([MPP] = 4 x 10(-)(5) M, and [PNPDPP] = 1 x 10(-)(5) M) for the PNPDPP cleavages are the following: buffer alone, 0.00034 s(-)(1); micelle: 0.024 s(-)(1); ME: 0.0048 s(-)(1); and vesicle: 0.025 s(-)(1). Importantly all the catalytic formulations showed "turnover" behavior in the presence of excess substrates. By the combined use of (1)H- and (31)P-NMR spectrometry and synthesis, it was possible to provide evidence for the formation of acylated or phosphorylated monoperoxypthalates in the catalytic hydrolyses in cationic surfactant aggregates.
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