Diene

In organic chemistry, a diene (/ˈdaɪ.iːn/ DY-een) or diolefin (/daɪˈoʊləfɪn/ dy-OH-lə-fin) is a hydrocarbon that contains two carbon pi bonds. Conjugated dienes are functional groups, with a general formula of C_nH_2n-2. Dienes and alkynes are functional isomers. Dienes occur occasionally in nature but are widely used in the polymer industry.

Dienes can be divided into three classes, depending on the relative location of the double bonds:

1. Cumulated dienes have the double bonds sharing a common atom as in a group of compounds called allenes.
2. Conjugated dienes have conjugated double bonds separated by one single bond.
3. Unconjugated dienes have the double bonds separated by two or more single bonds. They are usually less stable than isomeric conjugated dienes.

Compounds that contain more than two double bonds are called polyenes. Polyenes and dienes, share many of their properties.

An important reaction for conjugated dienes is the Diels–Alder reaction. Many specialized dienes have been developed to exploit this reactivity for the synthesis of natural products, e.g. Danishefsky’s diene.

• IUPACs Gold Book definition of dienes dienes PDF Archived 2007-06-09 at the Wayback Machine