merkaptane

Mercaptans, also known as thiols, are a class of organic compounds that contain a sulfhydryl group (-SH) bonded to carbon. The general structure is R–SH, where R denotes an organic substituent. The -SH group gives mercaptans distinctive chemical reactivity and, in many cases, a strong, often unpleasant odor. Thiols range from simple low-molecular-weight species, such as methanethiol and ethanethiol, to larger, more complex molecules.

Properties of mercaptans include relatively low boiling points for their size, high volatility, and acidity comparable to that of other weak acids (pKa around 10). They readily form thiolate anions in the presence of bases and can be oxidized to form disulfides (R–S–S–R), a reversible redox process relevant in biochemistry and materials chemistry. Their sulfur-containing functional group also makes them nucleophilic and prone to substitution and addition reactions.

Industrial production and sources vary. Mercaptans occur as byproducts in petroleum refining and natural gas processing, where their presence is often undesirable due to their strong odor. They can also be synthesized intentionally through methods such as hydrothiolation of alkenes with hydrogen sulfide or the thiourea route for preparing primary thiols from alkyl halides.

Applications include their use as odorants for natural gas and LPG to enable leak detection, and as intermediates in the manufacture of pharmaceuticals, agrochemicals, and polymers. They also find use in some flavor and fragrance formulations. Safety considerations are important: mercaptans are highly odorous and can be irritating or toxic at sufficient concentrations; they are flammable and can form corrosive or reactive mixtures with other chemicals, requiring appropriate handling and ventilation.