Thiolgruppe

The thiol group, also known as the sulfhydryl group, is a functional group in organic chemistry characterized by a sulfur atom bonded to a hydrogen atom and to the rest of the molecule as -SH. It is the sulfur analogue of the hydroxyl group found in alcohols. Thiols occur in a wide range of compounds, from simple mercaptans such as ethanethiol to the cysteine residues that are part of proteins.

Chemically, the S–H bond in thiols is typically weaker than the O–H bond in alcohols, and thiols can lose a proton in basic environments to form a thiolate anion (RS−). This anion is a soft nucleophile and participates readily in alkylation, acylation, and conjugate additions. Thiols are also prone to oxidation, forming disulfides (R–S–S–R), a reaction that plays a crucial role in protein folding and redox biology. In addition, thiols can engage in thiol–ene chemistry and various metal coordination reactions.

Biologically, thiol groups are important for the function of many enzymes and structural proteins. Cysteine residues can form disulfide bonds that stabilize protein structure, and redox-active cysteines participate in catalytic cycles and signaling pathways.

Applications include surface chemistry and materials science (thiols form strong bonds with gold, enabling self-assembled monolayers), bioconjugation (thiol groups react with maleimides and other electrophiles), and the preparation and manipulation of organosulfur compounds. Safety considerations note that many thiols have strong, unpleasant odors and can be toxic in certain contexts.