In chemistry, a disulfide ion is an anion (negatively-charged ion) formed by two sulfur atoms having an overall -2 charge. The term disulfide can also refer to a chemical compound which contains a disulfide ion or contain two sulfur atoms, usually bonded together.

Sulfur is usually reduced to a state with oxidation number -2 and forms a S^-2 ion, called a sulfide ion, which has the electron configuration of a noble gas (argon).

In some cases 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. 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. Such organic compounds are often biologically occurring.

The tendency is a bit more elaborate in the case of sulfur, which can form polysulfides.

Some examples

• An example of an inorganic disulfide compound is cadmium disulfide (CdS₂).
• An inorganic example with covalent bonds is disulfur dichloride (S₂Cl₂) - a yellow liquid with a foul odor used in vulcanization of rubber.
• An example of an organic compound containing a disulfide bond or group is the biological amino acid cystine.
• The compound carbon disulfide (CS₂) has a covalently bonded molecule similar to carbon dioxide except both oxygen atoms are replaced by sulfur atoms.

See also

• Disulfide bond

Reference

• Sulfur Halides (continued)