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Historically, the chemistry of phosphate transfera classof reactions fundamental to the chemistry of Lifehas beendiscussed almost exclusively in terms of the nucleophile and the leavinggroup. Reactivity always depends significantly on both factors; butrecent results for reactions of phosphate triesters have shown thatit can also depend strongly on the nature of the nonleaving or “spectator”groups. The extreme stabilities of fully ionised mono- and dialkylphosphate esters can be seen as extensions of the same effect, withone or two triester OR groups replaced by O–. Ourchosen lead reaction is hydrolysis–phosphate transfer to water:because water is the medium in which biological chemistry takes place;because the half-life of a system in water is an accepted basic indexof stability; and because the typical mechanisms of hydrolysis, withsolvent H2O providing specific molecules to act as nucleophilesand as general acids or bases, are models for reactions involvingbetter nucleophiles and stronger general species catalysts. Not leastthose available in enzyme active sites. [ABSTRACT FROM AUTHOR]

Palladium nanoparticles (NPs) with an average size of 3.4 nm were prepared in water using imidazolium-based surfactant 3-(1-dodecyl-3-imidazolio)propanesulfonate (ImS3-12) as a stabilizer. The Pd NPs are highly dispersible in water and chloroform and were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffraction, and dynamic light scattering. The results indicate that in water the NP surface is covered with a double layer of ImS3-12molecules. The NPs were effective in the aqueous biphasic hydrogenation of cyclohexene, with easy recycling and no loss of catalytic activity after four successive runs. [ABSTRACT FROM AUTHOR]

A polyhydroxamicalkanoate (PHA) polymer containing the functional groups hydroxamic acid and carboxylic acid with the ability to accelerate dephosphorylation reactions is proposed. The methodology used to prepare this polymer favored the position of the two functional groups next to each other, which allows for the cooperativity between these groups. This cooperative effect has an important role when one wants to mimic enzymes. The catalytic effect promoted by the polymer was evaluated on the cleavage of the bis(2,4-dinitrophenyl) phosphate (BDNPP) and diethyl 2,4-dinitrophenyl phosphate (DEDNPP) esters. Indeed, PHA was very efficient and promiscuous because it increased the rate of both reactions by a factor of up to 106-fold. Isothermal titration calorimetry (ITC) experiments showed that the presence of PHA aids the formation of cetyltrimethylammonium bromide (CTABr) micelles. Thus, the effect of the cationic surfactant CTABr on the dephosphorylation of BDNPP by PHA was also investigated, and it was observed that, when CTABr is added to PHA, the reaction is ca. 15-fold faster compared to the reaction when only PHA is present. [ABSTRACT FROM AUTHOR]

Synthesis of a new zwitterionic surfactant containing the imidazolium ring 3-(1-tetradecyl-3-imidazolio)propanesulfonate (ImS3-14) is described. The solubility of ImS3-14 is very low but increases on addition of a salt which helps to stabilize the micellized surfactant. Fluorescence quenching and electrophoretic evidence for ImS3-14 shows that the micellar aggregation number is only slightly sensitive to added salts, as is the critical micelle concentration, but NaClO4markedly increases zeta potentials of ImS3-14 in a similar way as in N-tetradecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-14) micelles. The rate of specific hydrogen ion catalyzed hydrolysis of 2-(p-heptoxyphenyl)-1,3-dioxolane and equilibrium protonation of 1-hydroxy-2-naphthoate ion in zwitterionic micelles of ImS3-14 and SB3-14 are increased markedly by NaClO4which induces anionoid character and uptake of H3O+, but NaCl is much less effective in this respect. Comparison of ImS3-14 with SB3-14 is based on experimental evidence, and computational calculations indicate similarities and differences in structures of both compounds. [ABSTRACT FROM AUTHOR]

Hexadecyl phosphorylcholine (HPC) micelles incorporate anions rather than cations in the interfacial region, giving an anionoid micelle with a negative zeta potential. Hydronium ion incorporation in the micellar pseudophase parallels the increase in the negative zeta potential, and salts increase the rate of A1 hydrolysis of 2-(p-heptyloxyphenyl)-1,3-dioxolane in micellized HPC and inhibit the reaction of OH−with naphthoic anhydride. The kinetic effects are larger with NaClO4than with NaCl. The increased micellar negative charge with added salts increases the repulsion between headgroups and decreases the aggregation number. These observations are relevant to understanding the behaviors of biological phosphorylcholine amphiphiles. [ABSTRACT FROM AUTHOR]

Mixed micelles of cetyltrisnethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the cc-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl)phosphate (BDNPP) over the pH range 4-10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 104-fold faster than its apontaneoua hydrolysis, and monoanionic LHA- is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, arid (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate. [ABSTRACT FROM AUTHOR]

In this work, we investigated the P−O bond cleavage of dianionic p-nitrophenyl phosphate monoester (p-NPP), with attack of aqueous methylamine on phosphorus, by using the hybrid quantum mechanical/effective fragment potential (QM/EFP) approach. We explored the structures, energetic properties, reaction mechanism, and charge distribution along the entire reaction coordinate. Our B3LYP/6-31(d,p)/EFP results show that the cleavage of the P−O bond of p-NPP proceeds through a concerted mechanism with an activation energy of about 26 kcal/mol and an activation free energy at 39 °C of 23.6 kcal/mol, in good agreement with the experimental value of 27 kcal/mol. The reaction involves a trigonal bipyramidal (TBP) transition state with less initial bonding to the nucleophile than to the leaving group. The extent of the P−O(nitrophenolate) bond dissociation at the transition state, with methylamine as the nucleophile, is less than that with OH−. The computed charge distribution along the reaction coordinate is consistent with a progressive charge transfer from the nitrogen atom of methylamine to the phosphate unit along the reaction coordinate. A new strategy to build the initial EFP cluster, by running a classical Monte Carlo simulation and analyzing the center-of-mass radial pair distribution function, was also used. [ABSTRACT FROM AUTHOR]

The reaction of I −with methyl naphthalene-2-sulfonate (MeONs) is accelerated by the micellized sulfobetaine surfactants N-decyl, N-dodecyl, N-tetradecyl, and N-hexadecyl- N, N-dimethylammonio-1-propanesulfonate. Concentrations of micellar-bound I −were determined by using ion-selective electrodes (ISE), and capillary electrophoresis. At low concentrations, I −incorporation fits Langmuir isotherms and is related to changes in micellar surface potentials. Rate effects of dilute KI are fitted quantitatively by a pseudophase model that describes I −binding in terms of a sorption isotherm, but at higher [KI], where the simple model predicts saturation, rates increase due to electrolyte invasion. This model considers transfer equilibria of both reactants between water and micelles and second-order rate constants in each pseudophase. Estimated second-order rate constants for reaction of MeONs with I −in the micellar pseudophase are 3.2- to 3.5-fold higher than the second-order rate constant, k2w, in water, depending on surfactant structure and assumptions in the treatment. [ABSTRACT FROM AUTHOR]

With fully micellar bound substrates reactions of OH-with benzoic anhydride, Bz2O, and of Br-with methyl naphthalene-2-sulfonate, MeONs, in micellized sulfobetaines are strongly inhibited by NaClO4which displaces the nucleophilic anions from the micellar pseudophases. Micellar incorporations of ClO4-and Br-are estimated with an ion-selective electrode and by electrophoresis, and partitioning of Br-between water and micelles is related to changes in NMR spectral 79Br-line widths. Extents of inhibition by ClO4-of these nucleophilic reactions in the micellar pseudophase are related to quantitative displacement of the reactive anions from the micelles by ClO4-. The kinetic data are correlated with physical evidence on the strong interactions between sulfobetaines and ClO4-, which turn sulfobetaine micelles anionic and effectively provoke displacement of OH-and Br-. [ABSTRACT FROM AUTHOR]

The rate of specific hydrogen ion catalyzed hydrolysis of 2-(p-heptoxyphenyl)-1,3-dioxolane and equilibrium protonation of 1-hydroxy-2-naphthoate ion in zwitterionic micelles of SB3-14, C14H29NMe2(CH2)3SO3-, are increased markedly by NaClO4which induces anionic character and uptake of H3Oin the micelles. Other salts, for example, NaNO3, NaBr, and NaCl, have similar but much smaller effects on this uptake of H3O. [ABSTRACT FROM AUTHOR]

The reaction of hydroxylamine with 2,4-dinitrophenyl diethyl phosphate gives the O-phosphorylated product, which is rapidly converted to hydrazine and nitrogen gas in the presence of the excess of hydroxylamine. [ABSTRACT FROM AUTHOR]