mercaptans

Mercaptans, more formally known as thiols, are a class of organosulfur compounds that contain a sulfhydryl group (-SH). The general formula is R-SH, where R is an alkyl or aryl group. The term mercaptan is historical, and thiol is the preferred systematic name in modern chemistry.

Thiols are typically characterized by their distinctive odors and relatively low acidity compared with alcohols. They are weak acids with pKa values around 10, and they can be deprotonated to form thiolate anions (RS−). They readily oxidize, forming disulfides (R-S-S-R) or further oxidized sulfur species. The chemistry of thiols also includes nucleophilic substitutions and additions, and they can participate in thioether formation and various sulfur-transfer reactions.

Occurrence and applications include their widespread use as odorants for natural gas, where compounds such as tert-butyl mercaptan and ethyl mercaptan provide a detectable smell at very low concentrations. Beyond odorization, thiols serve as important intermediates in organic synthesis and as precursors to sulfur-containing polymers and specialty chemicals. They are also employed in rubber chemistry and as reagents in various transformations.

Production and handling involve methods to introduce the thiol group, such as thiolation of alkyl halides or hydrothiolation of alkenes, and the reduction of disulfides. Thiols are generally flammable and can be toxic or irritating to eyes, skin, and the respiratory system; they should be handled with adequate ventilation and appropriate personal protective equipment.