Any organic compound having a sulfanyl group (–SH)
In organic chemistry, a thiol (/ˈθaɪɒl/;[1] from Ancient Greekθεῖον (theion) 'sulfur'[2]), or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SHfunctional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl (−OH) group of an alcohol), and the word is a blend of "thio-" with "alcohol".
Many thiols have strong odors resembling that of garlic or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans (/mərˈkæptæn/)[3] or mercapto compounds,[4][5][6] a term introduced in 1832 by William Christopher Zeise and is derived from the Latinmercurio captāns ('capturing mercury')[7] because the thiolate group (RS−) bonds very strongly with mercury compounds.[8]
German translation: Zeise, W. C. (1834). "Das Mercaptan, nebst Bermerkungen über einige neue Producte aus der Einwirkung der Sulfurete auf weinschwefelsaure Salze und auf das Weinöl" [Mercaptan together with comments on some new products from the effect of hydrogen sulfide on salts of ethyl sulfate ((C2H5)HSO4) and heavy oil of wine (a mixture of diethyl sulfate, diethyl sulfite, and polymerized ethylene)]. Annalen der Physik und Chemie. 2nd series (in German). 31 (24): 369–431. From p. 378: " … nenne ich den vom Quecksilber aufgenommenen Stoff Mercaptum (von: Corpus mercurio captum) … " ( … I name the substance [that is] absorbed by mercury "mercaptum" (from: the body (substance) [that] has been absorbed by mercury) … )
Zeise, William Christopher (1834). "Sur le mercaptan; avec des observations sur d'autres produits resultant de l'action des sulfovinates ainsi que de l'huile de vin, sur des sulfures metalliques" [On mercaptan; with observations on other products resulting from the action of sulfovinates [typically, ethyl hydrogen sulfate] as well as oil of wine [a mixture of diethylsulfate and ethylene polymers] on metal sulfides]. Annales de Chimie et de Physique. 56: 87–97. Archived from the original on 2015-03-20. "Mercaptan" (ethyl thiol) was discovered in 1834 by the Danish professor of chemistry William Christopher Zeise (1789–1847). He called it "mercaptan", a contraction of "corpus mercurio captans" (mercury-capturing substance) [p. 88], because it reacted violently with mercury(II) oxide ("deutoxide de mercure") [p. 92].