Organomercaptans

Organomercaptans, commonly referred to as mercaptans or thiols, are organic compounds in which a mercapto group (-SH) is attached to a carbon atom. The general formula is R-SH, where R is an organic substituent such as an alkyl, aryl, or allyl group. The –SH group imparts characteristic reactivity: thiols are more acidic than alcohols (pKa around 10) and readily form thiolate anions R-S− under basic conditions, which readily bind to soft metals to give metal-thiolate complexes. They are notable for their strong, often unpleasant odors.

Preparation methods include nucleophilic substitution of alkyl halides with thiourea followed by hydrolysis, direct hydrothiolation of alkenes, and reduction of thioesters or other sulfur-containing precursors. Organomercaptans can also be generated by exchanging functional groups in multistep thiolation reactions.

Reactions: Thiols oxidize to disulfides RSSR; they can undergo alkylation or arylation to form thioethers; deprotonation yields thiolate salts that act as ligands in coordination chemistry. They readily bind to many transition metals, forming metal-thiolate complexes.

Applications and occurrence: Mercaptans are widely used as odorants added to natural gas to provide a detectable smell at low concentrations. They serve as versatile intermediates in organic synthesis, providing access to thioethers, thioesters, and metal complexes. Safety: many mercaptans are malodorous and can be irritating or toxic at high concentrations; handle with appropriate ventilation and protective equipment. Environmental considerations include volatility and potential aquatic toxicity.