Disulfide
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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 S2− 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.
[edit] 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.
- Examples of organic compounds containing a disulfide bond or group are the biological amino acid cystine and lipoic acid.
- The compound carbon disulfide (CS2) has a covalently bonded molecule similar to carbon dioxide except both oxygen atoms are replaced by sulfur atoms.
