Thiocarboxylic acid
Thione form (carbothioic O-acid)
Thiol form (carbothioic S-acid)
In organic chemistry, thiocarboxylic acids or carbothioic acids are organosulfur compounds related to carboxylic acids by replacement of one of the oxygen atoms with a sulfur atom. Two tautomers are possible: a thione form (RC(S)OH) and a thiol form (RC(O)SH). These are sometimes also referred to as "carbothioic O-acid" and "carbothioic S-acid" respectively. Of these the thiol form is most common (e.g. thioacetic acid).
Thiocarboxylic acids are rare in nature, however the biosynthetic components for producing them appear widespread in bacteria. Examples include pyridine-2,6-dicarbothioic acid, and thioquinolobactin.