Benzene energy level diagrams

Compute the IIMO eigenvalues for benzene and draw its energy level diagram. 16. Draw the energy level diagram for pyrrole. 

Fig. 1.12. Energy level diagrams for cyclobutadiene and benzene, illustrating the application of Frost s circle.

FIGURE 3.39 The molecular orbital energy-level diagram for the ir-orbitals of benzene. In the ground state of the molecule, only the net bonding orbitals are occupied. 

Fio. 19. Comparison of the two lowest adiabatic ionization potentials in benzene with the three lowest in pyrrole and furan. The values arranged as an energy level diagram were obtained by photoelectron spectroscopy. (T, N. Badwan and D. W. Turner, unpublished work.)... 

The dehydrodimerization reaction involving aromatic radical-cations is fast only when electron donating substituents are present in the benzene ring. These substituents stabilise the a-intermediate. Benzene, naphthalene and anthracene radical-cations form a a-sandwich complex with the substrate but lack the ability to stabilise the a-intermediate so that radical-cation substrate reactions are not observed. The energy level diagram of Scheme 6.4 illustrates the influence of electron donating substituents in stabilising the Wheland type a-intermediate. 

Figure 6.4. Energy-level diagram for the molecular orbitals of benzene evaluated in the Huckel approximation.

The energy level diagram and the wavefunctions of the six n molecular orbitals in benzene. 

These then are the six Tt molecular orbitals for benzene. We can draw an energy level diagram to represent them. 

Now we can begin to put all the pieces together and make sense of what we know so far. Let us compare the energy level diagrams for benzene and planar cyclooctatetraene. We are not concerned with the actual shapes of the mole-cular orbitals involved, just the energies of them. 

Figure 3. MO energy level diagram for benzene, annotated in various ways.

Shown above is the energy-level diagram for the n orbitals of benzene, calculated on the basis of Hiickel molecular orbital theory. According to this theory, the total energy of the six n electrons of ground-state benzene is given by... 

Fig. 35. The n molecular orbitals according to Huckel MO calculations (kfi), energy level diagram (center) and term diagram of benzene with electronic transitions indicated (right). Quoted from [6]. Copyright John Wiley and Sons, Ltd. Reproduced with permission. The other parts are taken from Chang R (1971) Basic principles of spectroscopy. McGraw-Hill Kogakushi, Ltd, Tokyo. Reproduced with permission of the McGraw-Hill Companies...

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