Disulfide

Disulfide

[dahy-suhl-fahyd, -fid]
In chemistry, a disulfide usually refers to the structural unit composed of a linked pair of sulfur atoms. The disulfide anion is S22−. The term disulfide can also refer to a chemical compound that contains a disulfide center, such as diphenyl disulfide, C6H5S-SC6H5.

Sulfur is usually assigned to the reduced oxidation number −2, described as S2− 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 ion to form a disulfide (S2)2− group. Oxygen can also do this; e.g. in peroxides such as H2O2. 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 polysulfides.

Some examples

FeS2 unit cell
S2Cl2
cystine
lipoic acid
Ph2S2

Misnomers

Disulfide is also used to refer to compounds that contain two sulfide (S2−) centers. The compound carbon disulfide, CS2 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, MoS2, is not a disulfide in the sense again that its sulfur atoms are not linked.

CS2
MoS2

See also

References

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