Question

Explain resonance stabilization from the MO perspective

Answer 1

MO theory are intrinsically delocalized descriptions, and much of the qualitative picture we get from resonance forms is tied up in the numerical results: MO energies, atomic charges. etc

according to molecular orbital theory, some molecular orbitals may hold electrons that are more localized between specific pairs of molecular atoms and other orbitals may hold electrons that are spread more uniformly over the molecule. in MO theory bonding is far more delocalized, which makes it more applicable to resonant molecules that have equivalent non-integer bond orders than valence bond (VB) theory. This makes MO theory more useful for the description of extended systems. However, the shapes of the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital) along with the ESP map provide a qualitiative presentation of molecular properties and reactivity. It helps to make some comparisons of the descriptions from both directions.