Disulfider

Disulfider is a term occasionally encountered in chemical literature to denote compounds that contain a disulfide linkage, specifically a bond between two sulfur atoms (S–S) joining two substituent groups. In contemporary standard nomenclature, the preferred name for these compounds is disulfide; the form disulfider is comparatively rare and may appear in older texts, regional usages, or when the intent is to emphasize the sulfur–sulfur bond itself.

Chemical structure and properties

The defining feature of a disulfide is the S–S bond, which in simple diorganosulfides is typically around 2.0 Å in length. Each sulfur atom in R–S–S–R′ has an oxidation state near −1. The S–S bond is relatively weak compared with many carbon–carbon bonds and is readily cleaved by reductants to yield thiols. Disulfides can also undergo further oxidation under strong conditions, but in most contexts they participate in redox chemistry and thiol–disulfide exchange reactions.

Synthesis and reactivity

Disulfides are commonly prepared by the oxidation of thiols: 2 R–SH → R–S–S–R + 2 H+. They can also be formed by coupling of thiyl radicals or by coupling of sulfenyl intermediates under catalytic conditions. A characteristic feature is their ability to participate in thiol–disulfide exchange, where a thiol can break and reform S–S bonds: R′–S–S–R + HS–R′′ ⇌ R′–S–S–R′′ + R′′–SH. This dynamic covalent behavior underpins many applications in polymer chemistry and biochemistry.

Occurrence and significance

Disulfides occur widely in nature and industry. In biology, cystine is the disulfide formed between two cysteine residues and helps stabilize protein structure. In materials and organic synthesis, disulfide bonds serve as reversible crosslinks and functional handles for redox-responsive systems. The term disulfider remains uncommon; discrimination between disulfide and disulfider reflects evolving conventions in chemical nomenclature.