organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

, polyenes are polyunsaturated

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s that contain multiple carbon–carbon

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

s (). Some sources consider

diene In organic chemistry, a diene ( ); also diolefin, ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nome ...

s to be polyenes, whereas others require polyenes to contain at least three carbon–carbon double bonds. Conjugated polyenes contain a

conjugated system In physical organic chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases Chemical stability, stability. It is Reson ...

of alternating single and double carbon–carbon bonds, with characteristic optical properties. The following polyenes are used as antimycotics for humans:

amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococ ...

nystatin Nystatin, sold under the brand name Mycostatin among others, is an antifungal medication. It is used to treat ''Candida (fungus), Candida'' infections of the skin including diaper rash, Candidiasis, thrush, esophageal candidiasis, and vaginal ...

, candicidin, pimaricin, methyl partricin, and trichomycin.

Optical properties

Some polyenes are brightly colored, an otherwise rare property for a hydrocarbon. Normally alkenes absorb in the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

region of a

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

, 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 a

chromophore A chromophore is the part of a molecule responsible for its color. The word is derived . The color that is seen by our eyes is that of the light not Absorption (electromagnetic radiation), absorbed by the reflecting object within a certain wavele ...

). Thus many natural

dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...

s contain linear polyenes.

Chemical and electrical properties

Polyenes tend to be more reactive than simpler alkenes. For example, polyene-containing

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s are reactive towards atmospheric oxygen. Polyacetylene, which partially oxidized or reduced, exhibits high electrical conductivity. Most

conductive polymer Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The main advantage of conductive polymers ...

s are polyenes, and many have conjugated structures. Poly(aza)acetylenes are readily prepared from

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

precursors without the necessity of a controlled atmosphere, simply by

irradiation of a mixture of pyridine and poly(4-vinyl) pyridine. Recent research at the

Weizmann Institute The Weizmann Institute of Science ( ''Machon Weizmann LeMada'') is a Public university, public research university in Rehovot, Israel, established in 1934, fourteen years before the State of Israel was founded. Unlike other List of Israeli uni ...

and Aix-Marseille University showed a clear transition between ionic and electronic conductivity with increasing UV dose over 30 hours.

Occurrence

A few

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

s are polyenes. Another class of important polyenes are polyene antimycotics. File:Amphotericin B new.svg,

Amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococ ...

is an example of a polyene antifungal (antimycotic) agent. File:Leukotriene A4.svg,

Leukotriene Leukotrienes are a family of eicosanoid inflammation, inflammatory mediators produced in leukocytes by the redox, oxidation of arachidonic acid (AA) and the essential fatty acid eicosapentaenoic acid (EPA) by the enzyme arachidonate 5-lipoxyg ...

A4 is a regulator of the immune response. File:Trans-Polyacetylene.svg, Polyacetylenes are a synthetic polymer of theoretical interest because they exhibit metallic properties upon oxidation.Lam, Jacky W. Y.; Tang, Ben Zhong. "Functional Polyacetylenes", Accounts of Chemical Research, 2005, volume 38, pp. 745–754. .

References

{{Authority control Conjugated hydrocarbons