Dithiol

Last updated April 28, 2023

In organic chemistry, a dithiol is a type of organosulfur compound with two thiol (−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.

Geminal dithiols

Geminal dithiols have the formula RR'C(SH)₂. They are 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]

1,2-Dithiols

Compounds containing thiol groups on adjacent carbon centers are common. Ethane-1,2-dithiol reacts with aldehydes (−CH=O) and ketones (>C=O) to give 1,3-dithiolanes:

{\ce {(HS)2C2H4 + R-CHO -> R-CHS2C2H4 + H2O}}

Some dithiols are used in chelation therapy, i.e. the removal of heavy metal poisons.^[2] 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-dithiolate ^2- 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 (=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.^[3]

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

{\ce {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.

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.

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<span class="mw-page-title-main">Carboxylic acid</span> Organic compound containing a –C(=O)OH group

In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO₂H, with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.

<span class="mw-page-title-main">Ketone</span> Organic compounds of the form >C=O

In organic chemistry, a ketone is a functional group with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH₃)₂CO. Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.

In organic chemistry, an aldehyde is an organic compound containing a functional group with the structure R−CH=O. The functional group itself can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and are important in technology and biology.

In biochemistry, a disulfide refers to a functional group with the structure R−S−S−R′. The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of proteins. Persulfide usually refers to R−S−S−H compounds.

In organic chemistry, a thiol, or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols, and the word is a blend of "thio-" with "alcohol".

A diol is a chemical compound containing two hydroxyl groups. An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified.

Hydrogen peroxide - urea is a solid composed of equal amounts of hydrogen peroxide and urea. This compound is a white crystalline solid which dissolves in water to give free hydrogen peroxide. Hydrogen peroxide - urea contains solid and water-free hydrogen peroxide, which offers a higher stability and better controllability than liquid hydrogen peroxide when used as an oxidizing agent. Often called carbamide peroxide in the dental office, it is used as a source of hydrogen peroxide for bleaching, disinfection, and oxidation.

<span class="mw-page-title-main">Dithiothreitol</span> Chemical compound

Dithiothreitol (DTT) is the common name for a small-molecule redox reagent also known as Cleland's reagent, after W. Wallace Cleland. DTT's formula is C₄H₁₀O₂S₂ and the chemical structure of one of its enantiomers in its reduced form is shown on the right; its oxidized form is a disulfide bonded 6-membered ring (shown below). The reagent is commonly used in its racemic form, as both enantiomers are reactive. Its name derives from the four-carbon sugar, threose. DTT has an epimeric ('sister') compound, dithioerythritol (DTE).

<span class="mw-page-title-main">Carbonyldiimidazole</span> Chemical compound

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<span class="mw-page-title-main">Thiophenol</span> Chemical compound

Thiophenol is an organosulfur compound with the formula C₆H₅SH, sometimes abbreviated as PhSH. This foul-smelling colorless liquid is the simplest aromatic thiol. The chemical structures of thiophenol and its derivatives are analogous to phenols. An exception is the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, in the case of 'thiol' that the alcohol oxygen atom is replaced by a sulfur atom.

In organosulfur chemistry, thioacetals are the sulfur (thio-) analogues of acetals. There are two classes: the less-common monothioacetals, with the formula R−CH(−OR')−SR", and the dithioacetals, with the formula R−CH(−SR')₂ or R−CH(−SR')−SR".

<span class="mw-page-title-main">2-Mercaptoethanol</span> Chemical compound

2-Mercaptoethanol (also β-mercaptoethanol, BME, 2BME, 2-ME or β-met) is the chemical compound with the formula HOCH₂CH₂SH. ME or βME, as it is commonly abbreviated, is used to reduce disulfide bonds and can act as a biological antioxidant by scavenging hydroxyl radicals (amongst others). It is widely used because the hydroxyl group confers solubility in water and lowers the volatility. Due to its diminished vapor pressure, its odor, while unpleasant, is less objectionable than related thiols.

<span class="mw-page-title-main">Ethane-1,2-dithiol</span> Chemical compound

Ethane-1,2-dithiol, also known as EDT, is a colorless liquid with the formula C₂H₄(SH)₂. It has a very characteristic odor which is compared by many people to rotten cabbage. It is a common building block in organic synthesis and an excellent ligand for metal ions.

2,3-Dimercapto-1-propanesulfonic acid and its sodium salt are chelating agents that form complexes with various heavy metals. They are related to dimercaprol, which is another chelating agent.

<span class="mw-page-title-main">Dithiane</span> Chemical compound

A dithiane is a heterocyclic compound composed of a cyclohexane core structure wherein two methylene bridges are replaced by sulfur centres. The three isomeric parent heterocycles are 1,2-dithiane, 1,3-dithiane and 1,4-dithiane.

<span class="mw-page-title-main">1,2-Propanedithiol</span> Chemical compound

1,2-Propanedithiol, sometimes called 1,2-dimercaptopropane, is a thiol with the formula HSCH₂CH(SH)CH₃. This colorless, intensely odorous liquid is the simplest chiral dithiol. Related dithiols include 1,2-ethanedithiol, 2,3-dimercapto-1-propanesulfonic acid, and 1,3-propanedithiol. It is generated by the addition of H₂S to the related episulfide, CH₃CHCH₂S.

<span class="mw-page-title-main">Propane-1,3-dithiol</span> Chemical compound

1,3-Propanedithiol is the chemical compound with the formula HSCH₂CH₂CH₂SH. This dithiol is a useful reagent in organic synthesis. This liquid, which is readily available commercially, has an intense stench.

In organic chemistry, carbonyl reduction is the organic reduction of any carbonyl group by a reducing agent.

The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation of alcohols. Its use has subsided because milder, more selective reagents have been developed, e.g. Collins reagent.

References

↑ 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.
↑ 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.
↑ 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.

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[1] 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.

[2] 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.

[3] 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.

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