Disulfide - Inorganic Vs. Organic Disulfides

Inorganic Vs. Organic Disulfides

The disulfide anion is S₂2−, or −S–S−. 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 disulfide, sulfur is only reduced to a state with oxidation number −1. Its configuration then resembles that of a chlorine atom. It thus tends to form a covalent bond with another S− center to form S₂2− group. Oxygen also behaves similarly, e.g. in peroxides such as H₂O₂. Examples:

• Iron disulfide (FeS₂), e.g. the mineral pyrite.
• Disulfur dichloride (S₂Cl₂), a distillable liquid.

In many cases, each of the 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. Examples:

• The amino acid cystine
• The vitamin lipoic acid