page_title: Polysulfide
section_title: Organic polysulfides
hierarchical_section_title: Polysulfide / Organic polysulfides
context_page_description: Polysulfides are a class of chemical compounds containing chains of sulfur atoms. There are two main classes of polysulfides: anions and organic polysulfides. Anions have the general formula S²⁻
  ₙ. These anions are the conjugate bases of the hydrogen polysulfides H₂Sₙ. Organic polysulfides generally have the formulae RSₙR, where R = alkyl or aryl.
context_section_description: In commerce, the term "polysulfide" usually refers to a class of polymers with alternating chains of several sulfur atoms and hydrocarbons. They have the formula R₂Sₓ. In this formula x indicates the number of sulfur atoms (or "rank"). Polysulfide polymers can be synthesized by condensation polymerization reactions between organic dihalides and alkali metal salts of polysulfide anions:
  n Na₂S₅ + n ClCH₂CH₂Cl → [CH₂CH₂S₅]ₙ + 2n NaCl
  Dihalides used in this condensation polymerization are dichloroalkanes (such as 1,2-dichloroethane, bis-(2-chloroethyl)formal (ClCH₂CH₂OCH₂OCH₂CH₂Cl), and 1,3-dichloropropane).  The polymers are called thiokols. In some cases, polysulfide polymers can be formed by ring-opening polymerization reactions.
  Polysulfide polymers are also prepared by the addition of polysulfanes to alkenes. An idealized equation is:
  2 RCH=CH₂ + H₂Sₓ → (RCH₂CH₂)₂Sₓ
  In reality, homogeneous samples of H₂Sₓ are difficult to prepare.
  Polysulfide polymers are insoluble in water, oils, and many other organic solvents. Because of their solvent resistance, these materials find use as sealants to fill the joints in pavement, automotive window glass, and aircraft structures.
  Polymers containing one or two sulfur atoms separated by hydrocarbon sequences are usually not classified polysulfides, e.g. poly(p-phenylene) sulfide (C₆H₄S)ₙ.
caption: Lenthionine is an organic polysulfide found in shiitake mushrooms
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