MOLECULAR ORBITALS OF AROMATIC AND ANTIAROMATIC COMPOUNDS

Orbitals and have the same energy. They are antisymmetric and have one nodal plane. Each of the bonding MOs has two electrons. MOs 714, 715, and Tig have energy greater than zero. They are antibonding and contain no electrons. 

The cycloheptatrienyl cation contains 4 + 2 = 6 71 electtons. Therefore, it is aromatic. All three bonding k MOs are fully occupied, and the antibonding orbitals are empty. 

The cycloheptatrienyl anion contains 4 = 8 71 electrons, where = 2. Theiefore, it is an unstable antiaromatic species. All three bonding ti MOs are fully occupied, but the antibonding 714, 715 orbitals each have one electron. 

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