Molecular orbitals of benzene

FIGURE 114 The TT molecular orbitals of benzene arranged in order of increasing energy and showing nodal surfaces The six tt electrons of benzene occupy the three lowest energy or bitals all of which are bonding... 

Figure 2.27 Energy diagram molecular orbitals of benzene...

In general, a molecular-centered basis set is not suitable for constructing a function which does not approach spherical symmetry and have most of its structure close to the origin. For example, an extensive linear combination of molecule-centered atomiclike orbitals would be needed to construct the nodes in a b2g molecular orbital of benzene. Also, because the interference effects are specifically characteristic of the interplay between electron wavelength and the set of internuclear spacings, a molecule-centered basis set will not adequately describe interference effects. 

Esr spectra are subject to exchange effects in the same way as nmr spectra. A specific example is provided by electron exchange between sodium naphthalenide and naphthalene. Naphthalene has a set of ten 77-molecular orbitals, similar to the six 7r-molecular orbitals of benzene (Figure 21-5). The ten naphthalene it electrons fill the lower five of these orbitals. In a solvent such as 1,2-dimethoxyethane, which solvates small metal ions well, naphthalene accepts an electron from a sodium atom and forms sodium naphthalenide, a radical anion ... 

Example 6.2-1 This example discusses the molecular orbitals of benzene.The numbering system used for the atoms is shown in Figure 6.3. The point group of benzene is... 

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

The molecular orbitals of benzene are schematically represented in Fig. 3. The first excited state of benzene cannot be described by one electron configuration, due to the degeneracy of the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs). The Si state of benzene (B2u) can be represented as 4>24>4 - 4>35 and the S2 or state (Biu) as 4>24>5 - 4)3(t,4-... 

Figure 5 The frontier molecular orbitals of benzene and ethene.

The six tt molecular orbitals of benzene, viewed from above. The number of nodal planes increases with energy, and there are two degenerate MOs at each intermediate energy level. 

Energy diagram of the molecular orbitals of benzene. Benzene s six 77 electrons fill the three bonding orbitals, leaving the antibonding orbitals vacant. 

The difference between the amount of energy we expect to get out on hydrogenation (360 kj mol-1) and what is observed (208 kj mol-1) is about 150 kj mol-1. This represents a crude measure of just how extra stable benzene really is relative to what it would be like with three localized double bonds. In order to understand the origin of this stabilization, we must look at the molecular orbitals. We can think of the Jt molecular orbitals of benzene as resulting from the combination of the six p orbitals. We have already encountered the molecular orbital lowest in energy with all the orbitals combining in-phase. 

Figure 6-28. Contour diagrams of some molecular orbitals of benzene. Computer drawing by Zoltan Varga with Gaussview [29] (a) cr orbitals (b) tt orbitals.

Fig. 9.9 Energy diagram for the tt molecular orbitals of benzene and the regular hexagon analogue.

The six ir molecular orbitals of benzene were shown previously in F -ure 15.3, and their relative energies are shown again in Figure 15.11. The lowest-eneigy MO, > >]. occurs singly and contains two electrons. The next two lowest-energy orbitals, 1 2 / a- degenerate, and it therefore takes... 

Figure 12.8 The pi molecular orbitals of benzene. The view is from the side. The nodes are planes that go through the center and cut both sides of the loop.

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