Final answer:
Conjugated dienes feature carbon atoms with sp² hybridization, allowing for electron delocalization across the pi bonds due to the remaining unhybridized p-orbitals forming delocalized π bonds, as depicted in molecular orbital theory for 1,3-butadiene.
Step-by-step explanation:
Conjugated dienes are molecules in which alternate double and single carbon-carbon bonds occur consecutively, such as in 1,3-butadiene. In a conjugated diene, the carbon atoms participating in double bonds must have sp² hybridization. This hybridization involves one s-orbital and two p-orbitals on each carbon atom combining to form three sp² hybrid orbitals, leaving one p-orbital unhybridized. The unhybridized p-orbitals overlap laterally to form the delocalized π bonds, which are responsible for the distinct properties of conjugated systems such as the ability for electron delocalization.
In the context of molecular orbital (MO) theory, the electron delocalization in conjugated dienes can be exemplified by 1,3-butadiene, where the pi MO's result from combining the four 2p atomic orbitals. The lower two MO's are bonding, allowing for electron delocalization across the entire conjugated system, which is not possible in isolated double bonds.