Dienes or diolefins
which contain two double bonds
. Dienes are intermediate between alkenes
Dienes can be divided into three classes:
- Unconjugated dienes have the double bonds separated by two or more single bonds.
- Conjugated dienes have conjugated double bonds separated by one single bond. They are also the most stable.
- Cumulated dienes have the double bonds sharing a common atom as in a group of compounds called allenes.
- Heterodienes have one or more of the unsaturated carbon atoms replaced with a heteroatom.
In organic chemistry a conjugated diene is also a functional group. With a general formula of CnH2n-2. a classic organic reaction for the synthesis of dienes is the Whitening reaction.
1,3-butadiene undergoes 1,2-addition and 1,4-addition.
Reactions with dienes
The 1,3 configuration of double bonds found in 1,3-butadiene (conjugated double bonds) make these types of dienes capable of participating in more reaction types than is the case for molecules
with either just a single alkene functional group
or with multiple, but non-alternating, alkene groups. One possible reaction for such dienes is the Diels-Alder reaction
for example Danishefsky’s diene