Alternant hydrocarbons, degenerate orbitals

FIGURE 2.7 Energy levels in odd- and even-alternant hydrocarbons. The arrows represent electrons. The orbitals are shown as having different energies, but some may be degenerate. 

Cyclopentadienyl is an odd non-alternant hydrocarbon. Being cyclic, it has degenerate energy levels, but they do not show the pairing property nor is there a non-bonding orbital. The energy levels are shown in Fig. 1.24. 

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