Dithiols, reaction with lewisite

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. 

R. Jakubowski, Chemical reactions of chloroviny-larsines (Lewisite) 3. Reaction of Lewisite I and Lewisite II with dithiols, Umweltwissensch. Schadstoff-Forschung, 10, 198-199 (1998). 

Historically the first chromate dithiol reaction studied was that with BAL (British Anti-Lewisite) a chelating agent used in the treatment of arsenic(III) (Lewisite) and other cases of heavy metal poisoning ... 

A special derivatization reaction is required for lewisite 1, which is so reactive that it cannot be determined by GC/MS in low quantities (e.g. below 10 ng per injection). It has been known for a long time that lewisite 1 reacts with compounds having an a, P-dithiol structure, such as 2,3-dimercaptopropanol-l (British-Anti-Lewisite (BAL) also used for medical treatment). The derivatization reaction can be performed at an analytical level and several examples have been described (29). The reaction product of lewisite 1 with 3,4-dimercaptotoluene, 2-(2-chlorovinyl)-5-methyl-l,3,2-benzodithiarsole (see (1)), is a useful derivative for GC/MS analysis. Its mass spectrum is simple with molecular ion peaks at m/z 290/292 and the base peak at m/z 229 due to the loss of the 2-chlorovinyl group (30). 

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