thiolryhmien

A thiolryhmä, commonly referred to as a thiol group, is a functional group consisting of a sulfur atom bonded to a hydrogen atom, written as –SH, typically attached to a carbon skeleton (R–SH). Compounds containing one or more thiol groups are called thiols or mercaptans. The thiol group is analogous to the hydroxyl group of alcohols but exhibits distinct chemical properties due to the larger, more polarizable sulfur atom.

Properties and reactivity: Thiols are generally more acidic than alcohols. Aliphatic thiols have pKa values around 10.5, while aryl thiols can be substantially more acidic (often near 6–7) depending on substituents. The thiolate anion (RS−) is a strong nucleophile and can participate in a variety of reactions, including alkylation to form thioethers (R–S–R′) and acylation to yield thioesters (R–S–C(O)–R′). Oxidation of thiols readily forms disulfides (R–S–S–R), and further reactions can produce polysulfides. Thiols are frequently malodorous and many are volatile.

Occurrence and roles: In biology, thiol groups are found in cysteine residues of proteins, where they can form disulfide bonds that influence protein folding, stability, and redox regulation. Thiols also coordinate to metal centers, contributing to the function of metalloproteins and enzymes. In industry and synthesis, thiols serve as nucleophiles in many organic transformations and are used in odorants for gas detection, flavors, and fragrances.

Safety and handling: Thiols can be toxic and are often highly odorous; appropriate ventilation and handling precautions are advised in laboratory and industrial settings.