sulfanyl

Sulfanyl is a functional group in organic chemistry defined by a sulfur atom bonded to a hydrogen and to the rest of the molecule, written as -S-H. In systematic IUPAC nomenclature, the -SH substituent can be named sulfanyl, while if the thiol group is the principal functional group the compound is usually named as a thiol (often referred to by the common name mercaptan as well). The sulfanyl substituent thus represents the sulfur analogue of the hydroxyl group, and its use helps distinguish substituent positions from the main thiol functional group in complex molecules.

Sulfanyl and thiol chemistry

Compounds containing an -SH group are collectively called thiols. They are typically volatile and have distinct, often strong odors. The sulfur atom imparts nucleophilicity to the sulfur center, and aliphatic thiols have relatively acidic protons with pKa values around 10–11, making deprotonation to form thiolate ions feasible under basic conditions. Thiols readily oxidize to form disulfides (R-S-S-R), a reaction central to redox biology and protein structure. The -SH group can also participate in alkylation, reduction, and various condensation reactions that install sulfur-containing functionalities.

Occurrence and applications

Thiols occur widely in nature, for example in the amino acid cysteine and in many volatile plant and animal metabolites. Industrially, they serve as odorants for natural gas and other products, and they are used as building blocks in organic synthesis to introduce sulfanyl functionality. Disulfide bonds between cysteine residues are critical for the three-dimensional structure of many proteins.

Safety

Sulfanyl/thiol compounds can be toxic and irritating in vapors and are typically flammable. Proper handling and containment are advised.

See also

Thiol, mercaptan, disulfide, thioether.