An octadecatrienoic acid is a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

s with formula , a fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

 with whose molecule has an 18-carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 unbranched backbone with three double bonds.

The name refers to many different structural and conformational isomers, that differ in the position of the double bonds along the backbone and on whether they are in cis ('Z') or trans ('E') conformation. Some isomers have considerable biological, pharmaceutical, or industrial importance, such as:

• α-Linolenic acid
  Alpha-linolenic acid
  α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....
  
   (9Z,12Z,15Z), found in many cooking oil
  Cooking oil
  Cooking oil is purified fat of plant origin, which is usually liquid at room temperature ....
  
  s
• γ-Linolenic acid
  Gamma-Linolenic acid
  γ-Linolenic acid is a fatty acid found primarily in vegetable oils...
  
   (6Z,9Z,12Z), found in the evening primrose
  Evening Primrose
  Evening Primrose is a musical with a book by James Goldman and lyrics and music by Stephen Sondheim. It is based on a John Collier short story published in the 1951 collection Fancies and Goodnights....
  
   (Oenothera biennis)
• α-Eleostearic acid (9Z,11E,13E), the main component of tung oil
  Tung oil
  Tung oil or China wood oil is a drying oil obtained by pressing the seed from the nut of the tung tree . As a drying oil, tung oil hardens upon exposure to air. The resulting coating is transparent plastic-like and is exploited in most of its applications, which include wood finishing and the...
  
  .
• β-Eleostearic acid
  Beta-Eleostearic acid
  β-Eleostearic acid, or -octadeca-9,11,13-trienoic acid, is an organic compound with formula or H3C-33-7-OH. It is the all-trans conformational isomer of octadecatrienoic acid.-See also:...
  
   (9E,11E,13E)
• α-Calendic acid
  Calendic acid
  Calendic acid is an unsaturated fatty acid, named for the pot marigold , from which it is obtained. It is chemically similar to the conjugated linoleic acids; laboratory work suggests it may have similar health benefits.-Biosynthesis:Calendic acid is an omega-6 fatty acid...
  
   (8E,10E,12Z), found in the pot marigold (Calendula officinalis)
• 9,12,15-Octadecatrienoic acid, a cigarette additive.