- Solvent deuterium kinetic isotope effects for the methanolyses of neutral C=O, P=O and P=S esters catalyzed by a triazacyclododecane : Zn 2+-methoxide complex
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The methanolyses of several organophosphate/phosphonate/phosphorothioate esters (O, O-diethyl O-(4-nitrophenyl) phosphate, paraoxon, 3; O, O-diethyl S-(3,5-dichlorophenyl) phosphorothioate, 4; O-ethyl O-(2-nitro-4-chlorophenyl) methylphosphonate, 5; O, O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, fenitrothion, 6; O-ethyl S-(3,5-dichlorophenyl) methylphosphonothioate 7) and a carboxylate ester (p-nitrophenyl acetate, 2) catalyzed by methoxide and the Zn2+(-OCH3) complex of 1,5,9- triazacyclododecane (1 : Zn2+(-OCH3)) were studied in methanol and d1-methanol at 25°C. In the case of the methoxide reactions inverse skie's were observed for the series with values ranging from 2 to 1.1, except for 7 where the kD/kH = 0.90 ± 0.02. The inverse kD/kH values are consistent with a direct nucleophilic methoxide attack involving desolvation of the nucleophile with varying extents of resolvation of the TS. With the 1 : Zn 2+(-OCH3) complex all the skie values are kD/kH = 1.0 ± 0.1 except for 7 where the value is 0.79 ± 0.06. Arguments are presented that the fractionation factors associated with complex 1 : Zn2+(-OCH3) are indistinguishable from unity. The skie's for all the complex-catalyzed methanolyses are interpreted as being consistent with an intramolecular nucleophilic attack of the Zn2+-coordinated methoxide within a pre-equilibrium metal : substrate complex. The Royal Society of Chemistry 2005.
- Maxwell, Chris,Neverov, Alexei A.,Brown, R. Stan
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p. 4329 - 4336
(2007/10/03)
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- Mechanistic studies of la3+- And Zn2+-catalyzed methanolysis of aryl phosphate and phosphorothioate triesters. Development of artificial phosphotriesterase systems
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The methanolyses of a series of O,O-diethyl O-aryl phosphates (2,5) and O,O-diethyl S-aryl phosphorothioates (6) promoted by methoxide and two metal ion systems, (La3+)2(-OCH3)2 and 4:Zn2+:-OCH3 (4 = 1,5,9- triazacyclododecane) has been studied in methanol at 25°C. Bronsted plots of the log k2 values vs. sspKa for the phenol leaving groups give βlg values of -0.70. -1.43 and -1.12 for the methanolysis of the phosphates and -0.63, -0.87 and -0.74 for the methanolysis of the phosphorothioates promoted by the methoxide, La 3+ and Zn2+ systems respectively. The kinetic data for the metal-catalyzed reactions are analyzed in terms of a common mechanism where there is extensive cleavage of the P-XAr bond in the rate-limiting transition state. The relevance of these findings to the mechanism of action of the phosphotriesterase enzyme is discussed. The Royal Society of Chemistry 2005.
- Liu, Tony,Neverov, Alexei A.,Tsang, Josephine S.W.,Brown, R. Stan
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p. 1525 - 1533
(2007/10/03)
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- Method of decomposing organophosphorus compounds
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Methods and kits for decomposing organophosphorus compounds in non-aqueous media at ambient conditions are described. Insecticides, pesticides, and chemical warfare agents can be quickly decomposed to non-toxic products. The method comprises combining the organophosphorus compound with a non-aqueous solution, preferably an alcohol, comprising metal ions and at least a trace amount of alkoxide ions. In a first preferred embodiment, the metal ion is a lanthanum ion. In a second preferred embodiment, the metal ion is a transition metal.
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- Billion-fold acceleration of the methanolysis of paraoxon promoted by La(OTf)3 in methanol
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The methanolysis of the insecticide paraoxon (2) was investigated in methanol solution containing varying [La(OTf)3] (OTf = -OS(O)2CF3) as a function of ssPH at 25 °C. Plots of the pseudo-first-order rate constants (k2obs) for methanolysis as a function of [La(OTf)3]total were obtained under buffered conditions from ssph 5.15 to 10.97, and the slopes of the linear parts of these were used to determine the second-order rate constants (k2obs) for the La3+-catalyzed methanolysis of 2. Detailed analysis of the potentiometric titration data of La(OTf)3 in methanol through fits to a multicomponent equilibrium mixture of dimers of general stoichiometry La3+2(-OCH3)n, where n assumes values of 1-5, gives the equilibrium distribution of each as a function of sspH. These data, when fit to a second expression describing k2obs in terms of a linear combination of individual rate constants k22:1, k22:2.....k22:n for the dimers, allow one to describe the overall catalytic profile in terms of the individual contributions. The most catalytically important species are the three dimers La3+2(-OCH3)1, La3+2(-OCH3)2, and La3+2(-OCH3)3. The catalysis of the methanolysis of 2 is spectacular: a 2 × 10-3 M solution of [La3+]total, at neutral ssPH, affords a 109-fold acceleration relative to the base reaction (t1/2 ≈ 20 s at ssPH 8.2) with excellent turnover. A mechanism of the catalyzed reaction involving the La3+2(-OCH3)2 species is proposed.
- Tsang, Josephine S.,Neverov, Alexei A.,Brown
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p. 7602 - 7607
(2007/10/03)
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- Reactivity of methoxide ion in concentrated methanolic solutions of Et4NOCH3 and Et4NCl
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Bimolecular rate constants k were determined for reactions of 4-nitrophenyl 4-toluenesulfonate, diethyl 4-nitrophenyl phosphate, and ethyl 4-nitrophenyl ethylphosphonate with tetraethylammonium methoxide Et4NOCH3 in methanol at 25°C over a wide range of Et4NOCH3 concentrations, where the reagent acts simultaneously as electrolyte, and at [Et4NOCH3] ≤ 0.1 M (reagent) with variation of Et4NCl (electrolyte) concentration. The relation logk = logk0 + b[Et4NX] is fulfilled up to [Et4NX] = 3.5 M, indicating that the electrolyte affects the reaction rate through restructurization of methanol as reaction medium.
- Savelova,Belousova,Simanenko,Popov
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p. 1790 - 1796
(2007/10/03)
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- Dichotomy in the reactivity of trivalent phosphorus compounds Z3P (Z = Ph, nBu, OR) observed in the photoreaction with a ruthenium complex
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Solutions of tris(2,2′-bipyridyl)ruthenium(II) dichloride (Ru2+) and various types of trivalent phosphorus compounds Z3P (Z = Ph, nBu, OR; 1) in methanol have been photolyzed with visible light at 20 °C under an argon atmosphere, resulting in the oxidation of I to the corresponding pentavalent oxo compounds Z3P=O and ligand exchange of Ru2+ with 1. The former process takes place via single-electron transfer (SET) from 1 to Ru2+ in the photoexcited state, Ru2+*, which gene-rates the radical cation intermediate Z3P*+ from 1. The latter results from nucleophilic attack of 1 upon Ru2+*. The results show that 1 can act either as an electron donor or as a nucleo-phile toward Ru2+*. The rate constants for both processes are estimated. An excellent linear correlation is found between the logarithm of the SET rate and the oxidation potential for both the aromatic and aliphatic trivalent phosphorus compounds examined here; the slope of the plot is much less negative than expected on the basis of Rehm-Weller theory. Such behavior in the SET rates is interpreted by comparison with SET quenching by amines. On the other hand, a dualparameter correlation analysis shows that the ligand exchange is regulated by both steric and electronic factors in 1. WILEY-VCH Verlag GmbH, 1997.
- Yasui, Shinro,Tsujimoto, Munekazu,Shioji, Kosei,Ohno, Atsuyoshi
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p. 1699 - 1707
(2007/10/03)
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- REACTION OF PROPOSED PHOSPHOROTHIOLATE S-OXIDE INTERMEDIATES WITH ALCOHOLS
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S-Oxide 2 is an extremely reactive intermediate.Its phosphorylation vs rearrangement rates, strongly depend upon the nature of the nucleophile.
- Segall, Yoffi,Casida, John E.
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p. 209 - 212
(2007/10/02)
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- MERCURIMETRY OF PHOSPHOROUS TRIESTERS AND OF SOME OTHER ORGANIC P(III) COMPOUNDS
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Non-hindered trialkyl(aryl)phosphites reduce mercuric acetate to metallic mercury in methanolic solution.The reaction is fast enough to allow direct titration by potentiometry, using a Pt electrode; adding a little Et3N is beneficial.Phosphorous diesters do not interfere, but halide ions disturb the titration.Alkylphosphonous dialkylesters behave like phosphorous triesters but dialkylphosphinous esters and trialkyl- or triarylposphines give rise only to complexes.The reaction products of the titration of (EtO)3P are mixed phosphates (MeO)n(EtO)3-nPO (n=0,1,2), AcOH, AcOMe, AcOEt, Me2O, MeOEt and Hg.The mechanism is discussed.
- Demarcq, M. C.
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- Phosphoric and Phosphinic Sulfonic Anhydrides - Reinvestigation and Corrections. Novel Methods of Synthesis
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Earlier works from this and other laboratories on phosphoric and phosphinic sulfonic anhydrides have been reinvestigated.It was found that no single reaction described in the past provides a general method for the production of mixed anhydrides RR'P(O)SO2R'' (3) in high yields of isolated products.The following three efficient synthetic procedures leading to pure anhydrides 3 are described: a) Trifluoromethanesulfonic acid promoted reaction of phosphinic acid 9 with sulfonic triazolides 10. b) Reaction of phosphinic and phosphoric imidazolides 13 with sulfonic acid 6. c) Reaction of 13 with sulfonic anhydride 15.All methods result in high yields.Some chemical properties of the anhydrides 3 are described.
- Dabkowski, Wojciech,Michalski, Jan,Radziejewski, Czeslaw,Skrypczynski, Zbigniew
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p. 1636 - 1643
(2007/10/02)
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- Synthetic Route to 2-Deoxyaldoses by Fluoride-Catalyzed Solvolysis of Enol-Phosphate Esters
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1-Alkenyl and phenyl phosphate esters undergo smooth cleavage of the phosphorous-oxygen linkage by fluoride-catalyzed alcoholysis to give aldehydes (ketones) and phenols, respectively.Application of this method provides a new route to 2-deoxyaldosugars from the enol-phosphates derived from vinylene carbonate telomers.Keywords -- vinylene carbonate telomer; 2-deoxyaldose; enol phosphate; cesium fluoride; aryl phosphate
- Mitsuo, Naoki,Abe, Yoshihiro,Takizawa, Takeo,Kunieda, Takehisa
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p. 1327 - 1330
(2007/10/02)
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