Dithiocarboxylic acid

Dithiocarboxylic acids are organosulfur compounds with the formula RCS2H. They are the dithia analogues of carboxylic acids. A closely related and better studied family of compounds are the monothiocarboxylic acids, with the formula RCOSH.

Dithiocarboxylic acids are about 3x more acidic than the monothiocarboxylic acids. Thus, for dithiobenzoic acid pKa = 1.92. Such compounds are commonly prepared by the reaction of carbon disulfide with a Grignard reagent:
 * RMgX + CS2 -> RCS2MgX
 * RCS2MgX + HCl -> RCS2H + MgXCl

This reaction is comparable to the formation of carboxylic acids using a Grignard reagent and carbon dioxide. Dithiocarboxylate salts readily S-alkylate to give dithiocarboxylate esters:
 * RCS2Na + R'Cl -> RCS2R' + NaCl

Aryldithiocarboxylic acids, e.g., dithiobenzoic acid, chlorinate to give the thioacyl chlorides.