Lewisite oxide

Lewisite 1 per se is never found in the environment. Figure 18 shows that this compound hydrolyzes rapidly on contact with moisture to 2-chlorovinyl arsonous acid, which in turn slowly dehydrates to lewisite oxide (syn. 2-chlorovinyl arsenous oxide) (16). Both 2-chlorovinyl arsonous acid and lewisite oxide are nonvolatile. The most frequently used method for the identification of CWC-related chemicals is based on gas chromatography (GC) in combination with mass spectrometry (GC/MS). Indirect GC/MS analysis of lewisite 1 requires sample preparation, which involves conversion of lewisite oxide to 2-chlorovinyl arsonous acid in an acidic environment, followed by derivatization (12). The obtained species is both volatile and thermally stable, and thus amenable to GC analysis. Often, a mercaptan reagent is used as a derivatization agent. The reaction with 3,4-dimercaptotoluene is shown in Figure 19. 

B.A. Tomkins, G.A. Sega and C.-H. Ho, Determination of Lewisite oxide in soil using solid-phase microextraction followed by gas chromatography with flame photometric or mass spectrometric detection, J. Chromatogr., A, 909, 13-28 (2001). 

The aqueous fraction from the neutral or alkaline liquid-liquid extraction, or another portion of the original sample is prepared for analysis of the sample for lewisite 1 (CAS 541-25-3), lewisite 2 (CAS 40334-69-8), and lewisite oxide (CAS 3088-37-7) (Figure 1, fraction 5). The pH of the sample is adjusted with hydrochloric acid to pH 2, the sample is filtered, and 0.1 ml of a freshly prepared solution containing 3,4-dimercaptotoluene (DMT, CAS 496-74-2) 5 mg ml-1 in acetone is added. The sample vial is shaken vigorously and allowed to stand for 10 min. Then one milliliter of n-hexane is added and the sample is shaken vigorously for 30 s every 10 min for 30 min. The hexane fraction is allowed to separate. The top hexane-water fraction is tiansferred to a new vial and centrifuged. After centrifugation, the hexane fraction is separated, dried, and submitted for analysis. 

The reaction product of arsenic trichloride (see Table 1) with 3,4-dimercaptotoluene, 2-chloro-5-methyl-l,3,2-benzodithiarsole, still contains an active chlorine atom, rendering its determination by GC/MS difficult. The derivatization reaction can also be carried out with 2-chlorovinylarsenic oxide (lewisite oxide, CAS 3088-37-7), which is one of the degradation products of lewisite 1. Thus, the highly reactive arsenous compounds can be detected as less reactive derivatives amenable to GC/MS. 

Lewisite [dichloro(2-chlorovinyl)arsine] is an organic arsenical known for its vesicant properties (Rosenblatt et al., 1975). It has a molecular weight of 207.32, vapor pressure of 0.58 mm HG at 25°C, a liquid density of 1,89 g/cm at 25°C, freezing point of -18°C, boiling point of 190°C, and is negligibly soluble in water (DA, 1974). The chemical structure of lewisite is shown below. Lewisite may occur as a trans-isomer and as a cis-isomer. In aqueous solutions, the cis-isomer undergoes photoconversion to the trans-isomer (Clark, 1989). hi the presence of moisture, lewisite is rapidly converted to the more stable but highly toxic lewisite oxide (2-chlorovinylarsenous acid) (Cameron et al., 1946). 

Althongh lewisite is only slightly soluble in water, 0.5 g/L (Rosenblatt et al., 1975), hydrolysis, resulting in the formation of lewisite oxide and HCl is rapid. Qi-Lewisite mnst be heated to over 40°C to react with NaOH to yield vinyl chloride, sodium arsenite, and acetylene (Rosenblatt et al., 1975). In aqneons solution, the cis isomer nndergoes a photoconversion to the trans isomer (Rosenblatt et al., 1975). Upon standing in water, the toxic trivalent arsenic of lewisite oxide is converted to the less toxic pentavalent arsenic (Epstein, 1956). 

Lewisite in soil may rapidly volatilize or may be converted to lewisite oxide due to moisture in the soil (Rosenblatt et al, 1975). The low water solubility suggests intermediate persistence in moist soil (Watson and Griffin, 1992). Both lewisite and lewisite oxide may be slowly oxidized to 2-chlorovinylarsonic acid (Rosenblatt et al, 1975). Possible pathways of microbial degradation in soil include epoxidation of the C=C bond and reductive deha-logenation and dehydrohalogenation (Morrill et al, 1985). Due to the epoxy bond and arsine group, toxic metabolites may result. Additionally, residual hydrolysis may result in arsenic compounds. Lewisite is not likely to bioaccumulate. However, the arsenic degradation products may bioaccumulate (Rosenblatt et al, 1975). 

Hydrogen chloride, thiodigylcol, sulfonium aggregates, 2-chlorovinylarsonous acid (CVAA), and Lewisite oxide based on HD and... 

Hydrolyzes to form Lewisite oxide (solid), which dissolves very slowly in water ... 

CVAA, 2-chlorovinylarsenious oxide (Lewisite oxide), and HCl (hydrochloric acid) ... 

With the removal of water, 2-chlorovinyl arsonous acid forms lewisite oxide (2-chlorovinyl... 

Once formed, lewisite oxide and polymerized lewisite oxide are relatively insoluble in water. Once dry, the oxide will probably not readily redissolve or form the acid in the environment. The degradation products (and impurities) of lewisite are listed in the Appendix, Table A2. 

Lewisite has vesicant properties as well as systemic toxicity. Because lewisite rapidly hydrolyzes to 2-chlorovinyl arsonous acid upon contact with moist surfaces, the toxic properties of lewisite may actually be those of 2-chlorovinyl arsonous acid (Fowler etal., 1991). Percutaneous LD50 values in small mammals range from 5 to 24 mg/kg (Marrs et al., 1996). Lewisite oxide most likely also has vesicant properties (US Army, 1974). The vesicant potency of lewisite degradation products compared to lewisite is... 

The current evaluation concludes that toxic hazards associated with a potential CWA release, regardless of origin (e.g. controlled storage, transport, demilitarization activity, deliberate terrorist event) are primarily a consequence of exposure to the toxic parent compound, and not to a degradation product. Lewisite oxide and EA 2192 are exceptions, but the degradation reaction yields for these products is not 1 1 ... 

Chlorovinyl arsenous oxide 2-Chlorovinyl arsenic oxide 2-Chlorovinyl arsine oxide 2-Chloroethenyl arsinic oxide Lewisite oxide C2H2AsC10 3088-37-7 Hydrolysis or dehydration of 2-chlorovinyl arsonous acid... 

Lewisite oxide polymer (C2H2AsC10) NA Polymer of lewisite oxide... 

Lewisite Lewisite was processed using a skid-mounted apparatus which could accept bulk liquid metered in from 1 ton cylinders. During October 1991, the agent was destroyed in a three-step neutralization process (1) conversion of lewisite to lewisite oxide (chlorovinyl arsine oxide) by addition of the agent to aqueous acidic hydrogen peroxide (2) removal... 

That report mentioned the reaction of arsenic chloride and acetylene and a tarry very poisonous substance that was produced. We now know this to be Lewisite oxide, or Ml oxide, one of the concerns at the AUES owing to its toxicity and stable nature. Capt. Lewis continues ... 

Wherever it is, fish are probably dying. As just one example, see the dolphin casualty shown in Photo 16 in the center photo section. The author suggests that the decline of commercial fish species off the U.S. East Coast is as much the result of all the chemical weapons sunk there as it is from overfishing. In the North Sea, commercial fishers are occasionally burned by clumps of mustard and Lewisite oxide sticking to their nets from the German stockpiles sunk there after World War II. 

Solid toxics can also be missed when shells are examined using only x-rays. Also, gases like arsine have been missed. Kieselgur is often mistaken for sand. Seemingly empty shells that were found intact should still be analyzed as their contents may have leaked out and left a residual toxin like Lewisite oxide, arsenic, mercury, or thiodiglycol. 

Water. Although lewisite is only slightly soluble in water, 0.5 g/L (Rosenblatt et al. 1975), hydrolysis resulting in the formation of lewisite oxide and HCl is rapid. The hydrolysis is complex, with a number of reversible reactions (Clark... 

Reaction of the dihydroxy compound is slower, eventually forming lewisite oxide (chlorovinyl arsenous oxide) and polymerized lewisite oxide ... 

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