Tiolen

Tiolen, commonly known in English as thiols, are a class of organosulfur compounds characterized by the presence of one or more sulfhydryl (-SH) groups bonded to carbon. The simplest member is methanethiol (CH3SH); most thiols have the general formula R-SH, where R is an alkyl or aryl group. In Dutch and several other languages, thiols are referred to as tiolen. Thiols are analogous to alcohols, with sulfur replacing the oxygen of the hydroxyl group, which leads to distinct properties and reactivity.

Thiols are typically characterized by strong, often unpleasant odors; several thiols contribute to the characteristic smells of decay, garlic, or skunk spray. They are relatively polar and can form hydrogen bonds, but their S–H bond is more acidic than the O–H bond of alcohols. The pKa of aliphatic thiols is around 10, making thiolates (RS−) moderately strong nucleophiles and bases. Thiols readily oxidize to disulfides (R–S–S–R), a process central to redox biology and protein structure. They can also react with alkylating agents to form thioethers (R–S–R′) and serve as ligands for soft metal ions through the sulfur atom.

Biologically and industrially, thiols play important roles. In biology, cysteine residues and the tripeptide glutathione contain thiol groups that participate in redox signaling and protein folding via disulfide bonds. In industry, mercaptans are used as odorants to scent natural gas and in various flavors and fragrances; many thiols, such as 2-mercaptoethanol, are also used as reducing agents in laboratory settings, though they require careful handling due to toxicity and strong odor.

Safety and handling considerations include potential toxicity, strong odors, and flammability. Proper ventilation and appropriate containment are advised when working with thiols.