Weblink 13.7 The p MOs of benzene and butadiene

In benzene MO1, MO2 and MO3 are occupied (MO2 and MO3 are degenerate).

In cyclobutadiene with a square geometry, MO1 is doubly occupied and there is one electron each in the degenerate orbitals MO2 and MO3.

In cyclobutadiene with a rectangular geometry, MO1 and MO2 are both doubly occupied. MO2 and MO3 are no longer degenerate.

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