* A conjugated molecule has single and double bonds occurring alternatively as in the following: -C=C-C=C-C=C-C=C- while a molecule have isolated double bonds does not have this feature, such as in -C=C-C=C-C=C-C=C-. A typical example of distinguishing the two types is shown in the structures of isomeric pentadienes:
|a conjugated diene containing||a non conjugated diene containing|
|conjugated double bonds||isolated double bonds|
In conjugated molecules resonance structures are considered which impart stabilization as compared to others in which isolated double bonds are present.
** Also called delocalization energy. You have already learnt about the delocalization of electrons while studying the orbital representation of benzene.
* This can be extended to γ hydrogen atoms in some cases.