Lewisite trans

FIGURE 19.6 Published analytical approaches for the analysis of CVAA in urine (a) reaction of lewisite (trans isomer shown) with water to form CVAA, (b) reactions of CVAA with various thiols, and (c) derivatization using HFBI. 

Smith et al. (34) studied three isomers (els-, trans-and, geminal) of a lewisite using GC/MS, GC/FTIR, and NMR. 

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). 

P-chlorovinyldichloroarsine. (l-chloro-2-di-chloroarsinoethane dichloro[2-chlorovinyl] arsine chlorovinylarsinedichloride Lewisite). Two isomers, probably cis and trans, are known. CICIfCIIAsCL... 

Environmental Fate. When manufactured by normal processes, commercial lewisite is composed of cis and trans isomers in the ratio of 10 90 and several impurities including bis(2- chlorovinyl)chloroarsine and tris(2-chlorovinyl)ar-sine (Rosenblatt et al. 1975). The chemical and physical properties of the two isomers are similar. 

The main product is j8-chIorovinyldichloroarsine with the trans isomer predominating. The proportion of the ds isomer is increased when other catal)rsts such as mercuric and cuprous chloride are used 180, 181, 182), though this is never very great. The Lewisite phase usually separates from the reaction mixture and this is believed to be the reason for the predominant formation of the dichloroarsine. If acetone is added to the reaction mixture separation of the Lewisite layer does not take place, and the main product is tris- -chlorovinylarsine 181). Mercuric-chloride-catalyzed addition appears to proceed through a mercurial intermediate 181). 

Lewisite [L or L-1 dichloro(2-chlorovinyl) arsine] is an arsenical vesicant developed early in the twentieth century. Lewisite occurs as cis- and trans-isomers, the t5T>ical ratio being 10 90. Several impurities, including bis(2-chlorovinyl)chloroarsine (L-2) and tris(2-chlorovi-nyl)arsine (L-3), are typically present. The chemical and physical properties of cis- and trans-isomers are similar. 

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