Thiosalicylic acid

Chemical properties

Thiosalicylic acid, (o-mercapto benzoic acid), a sulfur-yellow solid that softens at 158 °C (316 °F), has a melting point of 164 °C (327 °F). It sublimes, is slightly soluble in hot water but freely soluble in glacial acetic acid and alcohol, and yields dithiosalicylic acid, upon exposure to air.

The Uses of Thiosalicylic acid

Thiosalicylic acid acts as a trapping agent, which is useful in the desulfenylation of 3-indolyl sulfides. It is used to prepare macrocyclic diamides by condensation with diamines. Further, it is used as a precursor to drug, which finds application for the treatment of atherosclerosis and melanoma. In addition to this, it is involved in the preparation of vaccine preservative thiomersal and thioindigo dyestuff.

Definition

ChEBI: Thiosalicylic acid is a sulfanylbenzoic acid that is the 2-sulfanyl derivative of benzoic acid. It has a role as a non-narcotic analgesic and an antipyretic. It is a conjugate acid of a thiosalicylate(1-).

Preparation

Thiosalicylic acid can be prepared from anthranilic acid via diazotization followed by the addition of sodium sulfide and then reduction with zinc. It can also prepared by heating o-halogenated benzoic acids with alkaline hydrosulfide in presence of copper.

Synthesis Reference(s)

Journal of the American Chemical Society, 111, p. 654, 1989 DOI: 10.1021/ja00184a038
Chemical and Pharmaceutical Bulletin, 33, p. 5184, 1985 DOI: 10.1248/cpb.33.5184

Purification Methods

Crystallise the thio acid from hot EtOH (4mL/g), after adding hot distilled water (8mL/g) and boiling with charcoal. The hot solution is filtered, cooled, the solid is collected and dried in vacuo (P2O5). Crystallise it from AcOH and sublime in vacuo.[Beilstein 10 IV 272.]