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.[1]

Dithiocarboxylic acids are about 3x more acidic than the monothiocarboxylic acids. Thus, for dithiobenzoic acid pKa = 1.92.[2] Such compounds are commonly prepared by the reaction of carbon disulfide with a Grignard reagent:[3]

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:[4]

RCS2Na + R'Cl → RCS2R' + NaCl

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

References

  1. ↑ Grote, Johanna; Friedrich, Felix; Berthold, Katarína; Hericks, Loreen; Neumann, Beate; Stammler, Hans‐Georg; Mitzel, Norbert W. (2018). "Dithiocarboxylic Acids: An Old Theme Revisited and Augmented by New Preparative, Spectroscopic and Structural Facts". Chemistry – A European Journal. 24 (11): 2626–2633. doi:10.1002/chem.201704235. PMID 29266463.
  2. ↑ Matthys J. Janssen (1969). "Thiolo, Thiono and Dithio Acids and Esters". In Saul Patai (ed.). Carboxylic Acids and Esters. PATAI'S Chemistry of Functional Groups. pp. 705–764. doi:10.1002/9780470771099.ch15. ISBN 978-0-470-77109-9.
  3. ↑ Ramadas, S. R.; Srinivasan, P. S.; Ramachandran, J.; Sastry, V. V. S. K. (1983). "Methods of Synthesis of Dithiocarboxylic Acids and Esters". Synthesis. 1983 (8): 605–622. doi:10.1055/s-1983-30446. S2CID 96087227.
  4. ↑ Frederick Kurzer; Alexander Lawson (1962). "Thiobenzoylthioglycolic Acid". Org. Synth. 42: 100. doi:10.15227/orgsyn.042.0100.
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