W2013CHM2311 Part 5 Notes

Therefore according to resonance theory alone we

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Unformatted text preview: each of the MOs by combining the allyl fragments in- phase and out- of- phase. Benzene π- MO Diagram: Combina0on of Two Allyl Fragments Some Informa;on Ψ1 Ψ4 Ψ2 Ψ5 Ψ3 Ψ6 Energies: Ψ2 = Ψ3; Ψ4 = Ψ5 The π- system of a benzene ring is stabilized rela0ve to the π- system of isolated allyl fragments – i.e., electrons are in orbitals of lower energies. Since interac0on of the π - systems (i.e., delocaliza0on of electrons) results in stabiliza0on, benzene is said to be aroma9c. Orbital Appearance: You should be able to derive the appearances of each of the MOs by combining the allyl fragments in- phase and out- of- phase. HMO Theory Applica0on to Aroma0city & An0aroma0city The π MOs of cyclic conjugated hydrocarbons can be determined by combining the π MOs of chain fragments. If the occupied orbitals of the ring are lower in energy than the occupied orbitals of the chain fragments, the ring...
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