Polyene

This article is about the class of chemical compounds. For polyenes in antifungal therapy, seePolyene antimycotic.For the ancient Macedonian writer, seePolyaenus.

Inorganic chemistry,polyenesare poly-unsaturated,organic compoundsthat contain at least three alternatingdouble(C=C) andsingle(C−C)carbon–carbon bonds.These carbon–carbon double bonds interact in a process known asconjugation,resulting in some unusualoptical properties.Related to polyenes aredienes,where there are only two alternating double and single bonds.

The following polyenes are used asantimycoticsfor humans:amphotericin B,nystatin,candicidin,pimaricin,methyl partricin, andtrichomycin.

Optical properties

Some polyenes are brightly colored, an otherwise rare property for a hydrocarbon. Normally alkenes absorb in theultravioletregion of aspectrum,but the absorption energy state of polyenes with numerous conjugated double bonds can be lowered such that they enter the visible region of the spectrum, resulting in compounds which are coloured (because they contain achromophore). Thus many naturaldyescontain linear polyenes.

Chemical and electrical properties

Polyenes tend to be more reactive than simpler alkenes. For example, polyene-containingtriglyceridesare reactive towards atmospheric oxygen.Polyacetylene,which partially oxidized or reduced, exhibits high electrical conductivity. Mostconductive polymersare polyenes, and many haveconjugatedstructures. Poly(aza)acetylenes are readily prepared frompyridineprecursors without the necessity of a controlled atmosphere, simply byultravioletirradiation of a mixture of pyridine and poly(4-vinyl) pyridine.Recent research at theWeizmann InstituteandAix-Marseille Universityshowed a clear transition between ionic and electronic conductivity with increasing UV dose over 30 hours.

Occurrence

A fewfatty acidsare polyenes. Another class of important polyenes arepolyene antimycotics,

• Representative polyenes
• 
  Amphotericin Bis an example of apolyene antifungal (antimycotic)agent.
• 
  LeukotrieneA4 is a regulator of the immune response.
• 
  Polyacetylenesare a synthetic polymer of theoretical interest because they exhibit metallic properties upon oxidation.