Sarin, hydrolysis

Sapphire polycrystals from radio-frequency plasma, 17 105, 106 Sarcophagine, 35 153 Sarin, hydrolysis of, 7 224-225 SIOOB, 46 453-454, 455 SlOOb, 46 453 54 SbBr, 41 235... 

Half-Times of First-Order Sarin Hydrolysis... 

Y. Matsuda, M. Nagao, T. Takatori, H. Niijima, M. Nakajima, H. Iwase, M. Kobayashi and K. Iwadate, Detection of sarin hydrolysis product in formalin-fixed brain tissues of victims of the Tokyo subway terrorist attack, Toxicol. Appl Pharmacol, 150, 310-320 (1998). 

Nagao M, Takatori T, Matsuda Y, Nakajima M, Niijima H, Iwase H, Iwadate K, Amano T. Detection of sarin hydrolysis products from sarin-like organophosphorus agent-exposed human erythrocytes. J Chromatogr B, 1997a 701 9-17. 

The calculated activation energy for the hydrolysis of sarin [43] on Amberlite-IRIOO is relatively low (22,000... 

The rate of hydrolysis of sarin on Dowex-50 cation exchange resin is insensitive to the stirring rate. However, with a more active catalyst (Amberlite-IRA 400), the rate constant at 20°C was 5.3, 7.5, and 8.5 h at 60,800 and 1000 revolutions/min , respectively, suggesting that film diffusion was the rate-limiting. step. Thus, the mechanism of the rate-limiting step depends on the nature of the catalyst [34]. 

Although the inhibition-based biosensors are sensitive, they are poor in selectivity and are rather slow and tedious since the analysis involves multiple steps of reaction such as measuring initial enzyme activity, incubation with inhibitor, measurement of residual activity, and regeneration and washing. Biosensors based on direct pesticide hydrolysis are more straightforward. The OPH hydrolyzes ester in a number of organophospho-rus pesticides (OPPs) and insecticides (e.g. paraoxon, parathion, coumaphos, diazinon) and chemical warfare agents (e.g. sarin) [53], For example, OP parathion hydrolyzes by the OPH to form p-nitrophenol, which can be measured by anodic oxidation. Rainina... 

This material is a degradation product from hydrolysis of VX (C01-A016) and Ethyl Sarin (C01-A005). 

The use of a lipophilic zinc(II) macrocycle complex, 1-hexadecyl-1,4,7,10-tetraazacyclododecane, to catalyze hydrolysis of lipophilic esters, both phosphate and carboxy (425), links this Section to the previous Section. Here, and in studies of the catalysis of hydrolysis of 4-nitrophenyl acetate by the Zn2+ and Co2+ complexes of tris(4,5-di-n-propyl-2 -imidazolyl)phosphine (426) and of a phosphate triester, a phos-phonate diester, and O-isopropyl methylfluorophosphonate (Sarin) by [Cu(A(A(A/,-trimethyl-A/,-tetradecylethylenediamine)l (427), various micellar effects have been brought into play. Catalysis of carboxylic ester hydrolysis is more effectively catalyzed by A"-methylimidazole-functionalized gold nanoparticles than by micellar catalysis (428). Other reports on mechanisms of metal-assisted carboxy ester hydrolyses deal with copper(II) (429), zinc(II) (430,431), and palladium(II) (432). 

The ester group is then hydrolysed, and the hydrolysis normally stops at the MePO(OH)2 stage. More vigorous conditions are required to rupture the Me—P bond. Thus the normal hydrolysis product of D.F.P. and of tabun, namely, phosphoric acid, will give a positive test with ammonium molybdate, whereas the product from sarin, namely, methylphosphonic acid, will not respond to this test. Vigorous reagents such as hot nitric acid and ammonium persulphate will break the C—P link and then a positive test for phosphate is obtained with ammonium molybdate. Sarin can be prepared in a variety of ways. Three... 

Other workers4 have recently shown that hydroxamic acid,. R-CONHOH, at pH 7-7 accelerates the hydrolysis of D.F.P. and sarin. They envisage the following reaction, although compound (I) has not been isolated. 

The P-atom in sarin (9.84), soman (9.85), and tabun (9.87) is a stereogen-ic center, allowing for stereoselective enzymatic hydrolysis [162], This aspect has been extensively investigated for soman, which exists as four stereoisomers by virtue of the presence of a second stereogenic center (C-atom). These stereoisomers are usually designated as C(+)P(-), C(-)P(+), C(+)P(+), and C(-)P(-), where C(+/-) refers to the 1,2,2-trimethylpropyl moiety and P(+/ ) to the P-atom. Such a nomenclature may be convenient but has no implication for the absolute configuration. The C(+)P( ) and Cf-)P(-) epimers are the more active toward acetylcholinesterase and, hence, the more toxic ones. In contrast, the C(+)P(+) and C(-)P(+) epimers are preferentially hydrolyzed... 

A hydroxoaqua copper complex containing N, N, N, A -tetramethyl-1,2-diamino-ethane (250) is an excellent catalyst for the hydrolysis of sarin, O-isopropyl methylphosphonofluoridate (251), and diethyl p-nitrophenyl phosphate (252 R = Et). The mechanism of the reaction probably involves bound hydroxide attacking the phosphoryl group with concomitant electrophilic catalysis by copper. 

The second-order rate constant for the reaction between sarin and either 2-PAM I or II was found to be 170 L/mol per minute. If a phosphorylated or phosphonylated oxime that does not enter rapidly into the second step above is formed, that product may be an Inhibitor of cholinesterase. 7,88 Hydrolysis of sarin in the presence of 200-fold concentrations of V and II took place more rapidly in plasma from rats with the former oxime than with the... 

Irreversible cholinesterases are mostly organophosphorus compounds and combine only with esteratic site of cholinesterase and that site gets phosphorylated. The hydrolysis of phosphorylated site produces irreversible inhibition of cholinesterase. And, because, of this property, the therapeutic usefulness is very limited. Most of the compounds are used as insecticides e.g. parathion, malathion and war gases e.g. tabun, sarin, soman etc. 

In the hydrolysis of the latter compound, Sarin, catalysis by cerous, cupric, and manganous ions in the form of bifunctional species which have a nucleophilic center (hydroxide ion) and an electrophilic center (M+) was particularly effective (19). Although the hydroxometallic ions are considerably weaker bases than hydroxide ion itself, they are catalytically more active by a factor of 10. This activity can be explained by the bifunctionality of these compounds mentioned above. 

Figure 1. Catalysis of Sarin and DFP hydrolysis by Cu(II) complexes plus 0H and/or hydroxo Cu(II) complexes...

The results of this type of analysis are expressed in Table I for the catalytic effects of Cu(II) chelates on the hydrolysis of Sarin (8) and DFP (6,8),... 

Table I . Third-Order Rate Constants Assigned to 1 1 Cu(ll) Chelates as Catalysts in the Hydrolysis of Sarin and DFP at 25°...

Metal ion catalysis of salicyl phosphate hydrolysis is much more complicated than that of Sarin, since the former substrate can combine with metal ions to give stable complexes, and some of the complexes formed do not constitute pathways for the reaction. In addition the substrate undergoes intramolecular acid-base-catalyzed hydrolysis which is dependent on pH because of its conversion to a succession of ionic species having different reaction rates. Therefore a careful and detailed equilibrium study of proton and metal ion interactions of salicyl phosphate would be required before any mechanistic considerations of the kinetic behavior in the absence and presence of metal ions can be undertaken. 

P. D Agostino et al., Determination of Sarin, Soman and their hydrolysis products in soil by packed capillary liquid chromatography-electrospray mass spectrometry. J. Chromatogr. A 912, 291-299 (2001)... 

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