tetradiene

Tetradiene is a nonstandard, informal term used in organic chemistry to denote a molecule that contains four carbon–carbon double bonds (four C=C units). It is not a precise IUPAC name; more specific names are used for concrete structures, such as octatetraene for a linear eight-carbon chain with four conjugated double bonds, or cyclooctatetraene for the eight-membered cyclic analogue.

Structure and isomerism

A tetradiene can be linear or cyclic and may exhibit different patterns of double-bond placement. The simplest well-known linear example is 1,3,5,7-octatetraene, CH2=CH–CH=CH–CH=CH–CH=CH2, in which all four double bonds are conjugated along the chain. Cyclic tetradienes include cyclooctatetraene (COT), C8H8, which has four C=C bonds arranged around a ring; in its planar form it would be antiaromatic, so the molecule typically adopts a nonplanar geometry to relieve that instability.

Reactivity

Tetradienes participate in many reactions typical of conjugated polyenes. They can undergo hydrogenation to reduce double bonds, electrophilic or radical additions, and various cycloaddition or Diels–Alder reactions when the structure presents a suitable diene component. Conjugated tetradienes exhibit characteristic UV–visible absorption and photochemical behavior that reflects extended pi-system delocalization.

Occurrence and synthesis

Longer polyenes are common in natural products and synthetic chemistry. The term tetradiene is more a descriptor of bond connectivity than a specific compound. In practice, chemists refer to named members such as octatetraene or cyclooctatetraene, and use general synthesis routes (elimination, cross-coupling, or sequential dehydrohalogenation) to prepare molecules containing four C=C bonds.

See also: polyene, diene, octatetraene, cyclooctatetraene.