Thiocarboxylic acid

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Carbothioic O-acid
Carbothioic S-acid

Thiocarboxylic acids are organosulfur compounds related to carboxylic acids by replacement of one oxygen centre by sulfur. There are two possible tautomers, RC(S)OH and RC(O)SH,[1] which are sometimes written as 'carbothioic O-acids' and 'carbothioic S-acids' respectively. The carbothioic S-acid tautomer RC(O)SH is far more common.

In the laboratory, the most common thiocarboxylic acid is thioacetic acid. A naturally occurring thiocarboxylic acid is 2,6-pyridinedicarbothioic acid, which functions as a siderophore. Thiocarboxylic acids are more acidic than the corresponding carboxylic acids.

Thiocarboxylic acids are typically prepared from the acid chloride:[2]

C6H5C(O)Cl + KSH → C6H5C(O)SH + KCl

Dithiocarboxylic acids[edit]

Dithiocarboxylic acids, with the formula RCS2H, are also known. They are less common than the monothio derivatives. Such compounds are commonly prepared by the reaction of carbon disulfide with a Grignard reagent:[3]

RMgX + CS2 → RCS2MgX
RCS2MgX + HCl → RCS2H + MgXCl

See also[edit]


  1. ^ Cremlyn, R.J. (1996). An introduction to organosulfur chemistry. Chichester: Wiley. ISBN 0-471-95512-4. 
  2. ^ Paul Noble, Jr., D. S. Tarbell (1963). "Thiobenzoic Acid". Org. Synth. ; Coll. Vol. 4, p. 924 
  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 (08): 605–622. doi:10.1055/s-1983-30446.