Lewisite reactions with thiols

The reactions with thiol groups (e.g., those that are found in proteins) form an alkylarsine sulfide. Mustard gas, at the same LCtso, induces vesication, whereas Lewisite does not. Apparently, Lewisite is more irritating initially to the pulmonary systems than mustard. The hydrolysis products are more persistent in soil in comparison with mustard. In ambient air. Lewisite is about 10 times more volatile than mustard. 

Trivalent arsenic forms strong bonds with sulfur, and thiols are therefore used for derivatizing both lewisite and CVAA, forming the same derivative (19). Lewisite reacts with mono and dithiols the reaction with dithiols occurring rapidly at ambient temperature. In a competitive environment, lewisite reacts almost exclusively with dithiols rather than monothiols (35). Three dithiols, 1,2-ethanedithiol, 1,3-propanedithiol and 2,3-dimercaptopropan-l-ol (British Anti-Lewisite, BAL) have been used for biomedical sample analysis of CVAA to form cyclic derivatives (14a, b) and (15). Unlike derivatiza-tion of TDG, CVAA can be derivatized direcdy in an aqueous solution. 2,3-Dimercaptotoluene, which has been used extensively for environmental analysis (19), does not appear to have been used. 

After sulfur and nitrogen mustards are absorbed and interact with body tissues, they are no longer intact molecules. Therefore, unlike nerve gas victims, the body fluids of decontaminated mustard-exposed patients pose no risk to health care providers or other responders (2). In contrast to the other vesicants, Lewisite does not require a cyclization reaction, so its effects are immediate. Through direct inhibition of thiol-containing enzymes. Lewisite disrupts energy pathways, causing ATP depletion, cell death, and clinical effects (15). 

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. 

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