Dithiol
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In organic chemistry, a dithiol is a type of organosulfur compound with two thiol (Page Module:Chem2/styles.css has no content.−SH) functional groups. Their properties are generally similar to those of monothiols in terms of solubility, odor, and volatility. They can be classified according to the relative location of the two thiol groups on the organic backbone.
- Structure of some dithiols
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Benzene-1,2-dithiol, the parent aromatic dithiol
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The drug meso-2,3-dimercaptosuccinic acid
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Dimercaprol ("British anti-Lewisite"), an early antidote for arsenic poisoning
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Dihydrolipoic acid, a vitamin
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Dithiothreitol, a reagent in protein biochemistry
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.[1] 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.[2]
1,2-Dithiols
Compounds containing thiol groups on adjacent carbon centers are common. Ethane-1,2-dithiol reacts with aldehydes (Page Module:Chem2/styles.css has no content.−CH=O) and ketones (Page Module:Chem2/styles.css has no content.>C=O) to give 1,3-dithiolanes:
Some dithiols are used in chelation therapy, i.e. the removal of heavy metal poisons.[3] 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 (Page Module:Chem2/styles.css has no content.=CH−) 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.[4]
Like 1,2-ethanedithiol, propanedithiol forms complexes with metals, for example with triiron dodecacarbonyl:
- Page Module:Chem2/styles.css has no content.Fe3(CO)12 + C3H6(SH)2 → Fe2(S2C3H6)(CO)6 + H2 + Fe(CO)5 + CO
A naturally occurring 1,3-dithiol is dihydrolipoic acid.
1,3-Dithiols oxidize to give 1,2-dithiolanes.[5]
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
- ^ Page Module:Citation/CS1/styles.css has no content.Magnusson, Bengt; Hassel, O.; Lindheim, A.; Kvande, P. C.; Meisingseth, E. (1963). "gem-Dithiols". Acta Chemica Scandinavica. 17: 273–275. doi:10.3891/acta.chem.scand.17-0273.
- ^ Page Module:Citation/CS1/styles.css has no content.Cairns, T. L.; Evans, G. L.; Larchar, A. W.; McKusick, B. C. (1952). "gem-Dithiols". Journal of the American Chemical Society. 74 (16): 3982–9. doi:10.1021/ja01136a004.
- ^ Page Module:Citation/CS1/styles.css has no content.Rooney, James P.K. (2007). "The role of thiols, dithiols, nutritional factors and interacting ligands in the toxicology of mercury". Toxicology. 234 (3): 145–156. doi:10.1016/j.tox.2007.02.016. PMID 17408840.
- ^ Page Module:Citation/CS1/styles.css has no content.Conrow, R. E.; Le Huérou, Y. (2004). "1,3-Propanedithiol". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. J. Wiley & Sons, New York. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237.
- ^ Page Module:Citation/CS1/styles.css has no content.Burns, John A.; Whitesides, George M. (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. 112 (17): 6296–6303. Bibcode:1990JAChS.112.6296B. doi:10.1021/ja00173a017.
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