Dithiol

Geminal dithiols

Geminal dithiols have the formula RR'C(SH)2. They are formally derived from aldehydes and ketones by the action of hydrogen sulfide. Their stability contrasts with the rarity of geminal diols. Examples include methanedithiol, ethane-1,1-dithiol, and cyclohexane-1,1-dithiol. Upon heating, gem-dithiols often release hydrogen sulfide, giving the transient thioketone or thial, which typically convert to oligomers.

1,2-Dithiols

Compounds containing thiol groups on adjacent carbon centers are common. Ethane-1,2-dithiol reacts with aldehydes () and ketones () to give 1,3-dithiolanes: :(HS)2C2H4 + R-CHO - R-CHS2C2H4 + H2O

Some dithiols are used in chelation therapy, i.e. the removal of heavy metal poisons. Examples include dimercaptopropanesulfate (DMPS), dimercaprol ("BAL"), and meso-2,3-dimercaptosuccinic acid.

Enedithiols

Enedithiols, with the exception of aromatic examples, are rare. The parent aromatic example is benzenedithiol. The dithiol of 1,3-dithiole-2-thione-4,5-dithiolate2- is also known.

1,3-Dithiols

Propane-1,3-dithiol is the parent member of this series. It is employed as a reagent in organic chemistry, since it forms 1,3-dithianes upon treatment with ketones and aldehydes. When derived from aldehydes, the methyne () group is sufficiently acidic that it can be deprotonated and the resulting anion can be C-alkylated. The process is the foundation of the umpolung phenomenon.{{cite encyclopedia

Like 1,2-ethanedithiol, propanedithiol forms complexes with metals, for example with triiron dodecacarbonyl: :

A naturally occurring 1,3-dithiol is dihydrolipoic acid.

1,3-Dithiols oxidize to give 1,2-dithiolanes.

1,4-Dithiols

A common 1,4-dithiol is dithiothreitol (DTT), HSCH2CH(OH)CH(OH)CH2SH, sometimes called Cleland's reagent, for to reduce protein disulfide bonds. Oxidation of DTT results a stable six-membered heterocyclic ring with an internal disulfide bond.

References

References

1. (1963). "gem-Dithiols". Acta Chemica Scandinavica.
2. (1952). "gem-Dithiols". Journal of the American Chemical Society.
3. (2007). "The role of thiols, dithiols, nutritional factors and interacting ligands in the toxicology of mercury". Toxicology.
4. (1990). "Predicting the stability of cyclic disulfides by molecular modeling: Effective concentrations in thiol-disulfide interchange and the design of strongly reducing dithiols". Journal of the American Chemical Society.