merkaptoniryhmänä

Mercapto group is a functional group in organic chemistry with the general formula R-SH. It consists of a sulfur atom bonded to a hydrogen atom and an alkyl or aryl group. The mercapto group is also known as a thiol group or sulfhydryl group. Thiols are the sulfur analogs of alcohols, where the oxygen atom is replaced by a sulfur atom.

Mercapto groups are known for their distinct and often unpleasant odor, which is characteristic of many thiols. This odor is due to the low molecular weight of many simple thiols. The sulfur atom in the mercapto group is capable of forming strong covalent bonds with other sulfur atoms, leading to the formation of disulfide bonds. This is a crucial reaction in biochemistry, particularly in the structure and function of proteins, where disulfide bonds help stabilize the three-dimensional structure.

Mercapto groups exhibit reactivity similar to hydroxyl groups in alcohols, but with some key differences due to the larger size and lower electronegativity of sulfur compared to oxygen. They can undergo oxidation, reduction, and nucleophilic substitution reactions. In biological systems, thiols are important antioxidants and play roles in enzyme activity and cellular signaling. For example, glutathione, a tripeptide containing a cysteine residue with a mercapto group, is a major intracellular antioxidant. The mercapto group can also act as a ligand, coordinating to metal ions, which is relevant in coordination chemistry and metalloenzymes.