Explanation:
Conjugated diene is the one that contains alternate double bonds in its structure. That means both the double bonds are separated by a single bond.
Cumulated diene is the one that contains two double bonds on a single atom. This means it has two double bonds continuously.
Isolated double-bonded compound has a single bond isolated by two to three single bonds.
Compound A: Two alkenes are joined by a sigma bond.
For example:
It is a conjugated diene.
Compound B: Two alkenes are joined by a C H 2 group.
It is a cumulative diene.
Compound C: Two alkenes are joined by C H 2 C H 2.
Then it is an isolated alkene.
Compound D: A cyclohexene has a double bond between carbons 1 and 2. Carbon 3 is an sp 2 carbon that is bonded to another s p 2 carbon with an alkyl substituent.
Hence, compound D is a conjugated diene.
