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Dithiin is a class of
Dithiin is a class of heterocyclic compound
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 ...
s, with the parent members having the formula (C2H2)2S2. Two isomers of this parent are recognized, 1,2- and 1,4-dithiins. Planar dithiins are 8π e− systems, which would lead to antiaromaticity
Antiaromaticity is a chemical property of a cyclic molecule with a π electron system that has higher energy, i.e., it is less stable due to the presence of 4n delocalised (π or lone pair) electrons in it, as opposed to aromaticity. Unlike aroma ...
if the structure was planar. Akin to the behavior of cyclooctatetraene
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...
, they instead adopt nonplanar structures. Vinyldithiin
Vinyldithiins, more precisely named 3-vinyl-4''H''-1,2-dithiin and 2-vinyl-4''H''-1,3-dithiin, are organosulfur phytochemicals formed in the breakdown of allicin from crushed garlic (''Allium sativum''). Vinyldithiins are Diels-Alder dimers of thi ...
, a common component of garlic, is a misnomer for 3-vinyl-4''H''-1,2-dithiin. 1,3-dithiins are unknown.
1,4-Dithiins
1,4-Dithiins have been more extensively studied. They are usually prepared by condensation of the equivalent of α-mercaptocarbonyls. For example, the acetal HSCH2CH(OEt)2 converts upon heating to the parent 1,4-dithiin. They are nonplanar and can be oxidized to theirradical cation
In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a ...
s. Photolysis
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by photons. It is defined as the interaction of one or more photons with one target molecule. ...
leads to dimerization via a +2cycloaddition
In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of th ...
. Thianthrene
Thianthrene is a sulfur-containing heterocyclic chemical compound. It is a derivative of the parent heterocycle called dithiin. It is notable for its ease of oxidation.
Structure and synthesis
Like other 1,4-dithiins but unlike its oxygen anal ...
is dibenzo-1,4-dithiin.
1,2-Dithiins
1,2-Dithiins are isomers of but-2-ene-dithials. They tend to be unstable with respect to loss of sulfur and formation of the thiophene derivative: :C4R4S2 → C4R4S + "S" They are often claret-colored. Some occur as flower pigments in plants of the familyAsteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...
.Block, Eric; Page, Jon; Toscano, John P.; Wang, Cun-Xiao; Zhang, Xing; DeOrazio, Russell; Guo, Chuangxing; Sheridan, Robert S.; Towers, G. H. Neil, "Photochemistry of Thiarubrine A and Other 1, 2-Dithiins: Formation of 2, 6-Dithiabicyclo .1.0ex-3-enes" Journal of the American Chemical Society 1996, vol. 118, pp. 4719-20. {{doi, 10.1021/ja960589v
References