dithiol

A dithiol is an organic compound that contains two thiol functional groups (-SH) in the same molecule. These compounds can be aliphatic, such as ethane-1,2-dithiol (ethanedithiol, C2H6S2) or propane-1,3-dithiol, or aromatic, such as benzene-1,2-dithiol (ortho-benzenedithiol, C6H4(SH)2). The defining feature is the presence of two -SH groups, which can participate in similar reactions as thiols and can also interact cooperatively in chemistries that involve both groups. Dithiols are distinct from disulfides, which contain an S–S linkage between sulfur atoms rather than two covalently bound -SH groups.

In coordination chemistry and related fields, the term dithiol is often used to describe dithiol-type ligands. When both thiol protons are removed (deprotonated), the resulting dithiolate can act as a strong, bidentate ligand that chelates metal centers or bridges between metals. Dithiols serve as useful building blocks and reagents in organic synthesis, and they are employed as protecting group handles, crosslinkers in polymers, or precursors to disulfides in various transformations.

Reactivity and properties: typical thiol pKa values are around 10, so dithiols can form thiolate anions under mild basic conditions. They readily oxidize in air to form disulfides (R-S-S-R). Many dithiols have characteristic odors and varying degrees of water solubility depending on their substituents. Handling of thiols generally follows standard laboratory precautions for malodorous sulfur compounds.

See also: thiol, disulfide, dithiolate.