organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

, a dithiol is a type of

organosulfur compound Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfu ...

with two

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...

()

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...

s. Their properties are generally similar to those of monothiols in terms of

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

, odor, and volatility. They can be classified according to the relative location of the two thiol groups on the organic backbone. File:C6H4(SH)2.svg, Benzene-1,2-dithiol, the

parent A parent is a caregiver of the offspring in their own species. In humans, a parent is the caretaker of a child (where "child" refers to offspring, not necessarily age). A ''biological parent'' is a person whose gamete resulted in a child, a male t ...

aromatic dithiol File:1,3-Propandithiol Structural Formula V1.svg,

Propane-1,3-dithiol 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. Use in organic synthesis 1,3-Prop ...

File:Meso-2,3-dimercaptosuccinic-acid-2D-skeletal-A-configurations-labelled.png, The drug meso-2,3-

dimercaptosuccinic acid Succimer, sold under the brand name Chemet among others, is a medication used to treat lead poisoning, lead, mercury poisoning, mercury, and arsenic poisoning. When radioactive tracer, radiolabeled with technetium-99m, it is used in a number of ...

File:Dimercaprol.svg,

Dimercaprol Dimercaprol, also called British anti-Lewisite (BAL), is a medication used to treat acute poisoning by arsenic, mercury, gold, and lead. It may also be used for antimony, thallium, or bismuth poisoning, although the evidence for those uses is not ...

("British anti-Lewisite"), an early antidote for arsenic poisoning File:Dihydrolipoic-acid-2D-skeletal.png,

Dihydrolipoic acid Dihydrolipoic acid is an organic compound that is the reduced form of lipoic acid. This carboxylic acid features a pair of thiol groups, and therefore is a dithiol. It is optically active, but only the R-enantiomer is biochemically significant. ...

, a vitamin File:Dithiothreitol.png,

Dithiothreitol 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 ...

, a reagent in protein biochemistry

Geminal dithiols

Geminal dithiols have the formula RR'C(SH)₂. They are derived from aldehydes and ketones by the action of

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

. Their stability contrasts with the rarity of geminal diols. Examples include

methanedithiol Methanedithiol is an organosulfur compound with the formula H2C(SH)2. It forms when formaldehyde is treated with hydrogen sulfide under pressure. The reaction competes with formation of trithiane. The compound forms a solid dibenzoate upon treat ...

ethane-1,1-dithiol Ethane-1,1-dithiol is an organosulfur compound with formula CH3CH(SH)2. It is a colourless smelly liquid that is added to or found in some foods. The compound is an example of a geminal dithiol. Use Flavouring uses of ethane-1,1-dithiol may in ...

, and cyclohexane-1,1-dithiol. Upon heating, gem-dithiols often release hydrogen sulfide, giving the transient

thioketone In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure ...

thial In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, , in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group). Thioaldehydes are even more rea ...

, which typically convert to

oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relativ ...

1,2-Dithiols

Compounds containing thiol groups on adjacent carbon centers are common.

Ethane-1,2-dithiol Ethane-1,2-dithiol, also known as EDT, is a colorless liquid with the Chemical formula, formula Carbon, CHydrogen, H(Thiol, SH). It has a very characteristic odor which is compared by many people to rotten cabbage. It is a common building block in ...

reacts with aldehydes () and ketones () to give 1,3-dithiolanes: :(HS)2C2H4 + R-CHO -> R-CHS2C2H4 + H2O Some dithiols are used in

chelation therapy Chelation therapy is a medical procedure that involves the administration of Chelation, chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very sp ...

, i.e. the removal of heavy metal poisons. Examples include dimercaptopropanesulfate (DMPS),

dimercaprol Dimercaprol, also called British anti-Lewisite (BAL), is a medication used to treat acute poisoning by arsenic, mercury, gold, and lead. It may also be used for antimony, thallium, or bismuth poisoning, although the evidence for those uses is not ...

("BAL"), and meso-2,3-

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

is the parent member of this series. It is employed as a reagent in organic chemistry, since it forms 1,3-

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

s upon treatment with ketones and

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

s. When derived from aldehydes, the

methyne In organic chemistry, a methine group or methine bridge is a trivalent functional group , derived formally from methane. It consists of a carbon atom bound by two single bonds and one double bond, where one of the single bonds is to a hydrogen. T ...

() 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 In organic chemistry, umpolung () or polarity inversion is the chemical modification of a functional group with the aim of the reversal of polarity of that group. This modification allows secondary reactions of this functional group that would oth ...

phenomenon. Like 1,2-ethanedithiol, propanedithiol forms complexes with metals, for example with

triiron dodecacarbonyl Triiron dodecarbonyl is the organoiron compound with the formula Fe3(CO)12. It is a dark green solid that sublimes under vacuum. It is soluble in nonpolar organic solvents to give intensely green solutions. Most low-nuclearity clusters are pale ...

: :Fe3(CO)12 + C3H6(SH)2 -> Fe2(S2C3H6)(CO)6 + H2 + Fe(CO)5 + CO A naturally occurring 1,3-dithiol is

dihydrolipoic acid Dihydrolipoic acid is an organic compound that is the reduced form of lipoic acid. This carboxylic acid features a pair of thiol groups, and therefore is a dithiol. It is optically active, but only the R-enantiomer is biochemically significant. ...

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

dithiolane A dithiolane is a sulfur heterocyclic compound, heterocycle derived from cyclopentane by replacing two methylene bridges (-- units) with thioether groups. The parent compounds are 1,2-dithiolane and 1,3-dithiolane. 1,2-Dithiolanes are cyclic disu ...

1,4-Dithiols

A common 1,4-dithiol is

dithiothreitol 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 ...

(DTT), HSCH₂CH(OH)CH(OH)CH₂SH, sometimes called

Cleland Cleland may refer to: Places * Cleland, South Australia, a suburb ** Cleland National Park, a protected area in South Australia ***Cleland Wildlife Park, a zoo within the area of Cleland National Park * Cleland, North Lanarkshire, a small village ...

's reagent, for to

reduce Reduction, reduced, or reduce may refer to: Science and technology Chemistry * Reduction (chemistry), part of a reduction-oxidation (redox) reaction in which atoms have their oxidation state changed. ** Organic redox reaction, a redox react ...

protein

disulfide bond In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . 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 ...

s. Oxidation of DTT results a stable six-membered

heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

ring with an internal

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References

Functional groups Organosulfur compounds