alkanethiols

Alkanethiols are a class of organosulfur compounds with the general formula R-SH, where R is an alkyl group. They are also known as alkyl thiols or mercaptans. The thiol group (-SH) is attached to a saturated carbon, giving primary, secondary, or tertiary thiols depending on the substitution at the carbon bearing the group. The systematic IUPAC name is alkane-1-thiol (for example, methane-1-thiol is methanethiol, ethane-1-thiol is ethanethiol).

Physical properties of alkanethiols include relatively strong, often unpleasant odors and appreciable volatility. Boiling points are higher than those of the corresponding alkanes due to hydrogen bonding involving the -SH group. Methanethiol and ethanethiol are appreciably soluble in water, while longer-chain thiols are less so. The pKa of thiols in water is about 10, meaning they form thiolate ions under basic conditions and behave as moderate acids.

Reactivity of alkanethiols centers on the thiol hydrogen and sulfur atom. They are good nucleophiles and readily react with alkyl halides to form thioethers (R–S–R′). Oxidation of two thiol molecules yields disulfides (R–S–S–R). Thiols can also act as soft ligands, binding to many transition metals, and they participate in various condensation and protective-group chemistry in organic synthesis.

Synthesis and occurrence: alkanethiols can be prepared by methods such as the thiourea route, which converts alkyl halides to thiols after hydrolysis, or by reduction of thioesters. They occur in nature and are widely used as odorants to give natural gas and propane a detectable odor, with compounds such as tert-butylthiol serving as common additives. Alkanethiols are important reagents in organic synthesis and coordination chemistry, and they require careful handling due to their malodorous and potentially toxic nature.