Disulfide
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2008-04-13T15:54:26Z
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In [[chemistry]], a '''disulfide''' usually refers to the structural unit composed of a linked pair of sulfur atoms. The disulfide [[anion]] is S<sub>2</sub><sup>2−</sup>. The term '''disulfide''' can also refer to a [[chemical compound]] that contains a [[disulfide bond|disulfide center]], such as [[diphenyl disulfide]], C<sub>6</sub>H<sub>5</sub>S-SC<sub>6</sub>H<sub>5</sub>.
Sulfur is usually assigned to the [[reduction (chemistry)|reduced]] [[oxidation number]] −2, described as S<sup>2−</sup> and called [[sulfide]]. It has the electron configuration of a [[noble gas]] ([[argon]]).
In disulfides, sulfur is only reduced to a state with oxidation number −1. Its configuration then resembles that of [[chlorine]] and, like it, has the tendency to form a covalent bond with another S<sup>−</sup> ion to form a disulfide (S<sub>2</sub>)<sup>2−</sup> group. [[Oxygen]] can also do this; e.g. in [[peroxide]]s such as H<sub>2</sub>O<sub>2</sub>. In many cases, each of the two sulfur atoms in a disulfide group is covalently bonded to a carbon atom in an [[organic compound]], forming a [[disulfide bond]], sometimes called a ''disulfide linkage'' or a ''disulfide bridge''.
The tendency is a bit more elaborate in the case of sulfur, which can form [[polysulfide]]s.
==Some examples==
*[[Iron]] disulfide (FeS<sub>2</sub>), known as the [[mineral]] [[pyrite]].
*[[Disulfur dichloride]] (S<sub>2</sub>Cl<sub>2</sub>), a distillable liquid.
*The amino acid [[cystine]]
*The [[vitamin]] [[lipoic acid]]
*[[Diphenyl disulfide]] (Ph<sub>2</sub>S<sub>2</sub>).
<center>
{|align="center" class="wikitable"
|<center>[[Image:Pyrite-unit-cell-3D-balls.png|100px]]</center>||<center>[[Image:Disulfur-dichloride-3D-balls.png|100px]]</center>||<center>[[Image:Cystine-3D-balls.png|100px]]</center>||<center>[[Image:Lipoic-acid-3D-balls.png|150px]]</center>||<center>[[Image:Diphenyl-disulfide-3D-balls.png|150px]]</center>
|-
|<center>FeS<sub>2</sub> [[unit cell]]</center>||<center>S<sub>2</sub>Cl<sub>2</sub></center>||<center>cystine</center>||<center>lipoic acid</center>||<center>Ph<sub>2</sub>S<sub>2</sub></center>
|}
</center>
==Misnomers==
Disulfide is also used to refer to compounds that contain two sulfide (S<sup>2−</sup>) centers. The compound [[carbon disulfide]], CS<sub>2</sub> is described with the structural formula i.e. S=C=S. This molecule is not a disulfide in the sense that it lacks a S-S bond. Similarly, [[molybdenum disulfide]], MoS<sub>2</sub>, is not a disulfide in the sense again that its sulfur atoms are not linked.
<center>
{|align="center" class="wikitable"
|<center>[[Image:Carbon-disulfide-3D-balls.png|200px]]</center>||<center>[[Image:Molybdenite-3D-balls.png|200px]]</center>
|-
|<center>CS<sub>2</sub></center>||<center>MoS<sub>2</sub></center>
|}
</center>
==See also==
* [[Disulfide bond]]
* [[Diphenyl disulfide]]
==References==
[[Category:Anions]]
[[de:Disulfide]]
[[it:Disolfuro]]
[[ja:ジスルフィド]]
[[fi:Disulfidi]]