Figure Number: 07-00CO Title: Benzene and Cyclohexane Caption: Potential maps around ball-and-stick models and structures of benzene and cyclohexane. Notes: Benzene has carbon–carbon sigma bonds with localized electrons and carbon–carbon pi bonds with delocalized electrons, whereas cyclohexane has only carbon–carbon sigma bonds with localized electrons.

Figure Number: 07-01a-d Title: Figure 7.1 Caption: Structure of benzene. Notes: a. Shows the sigma-bonding framework of benzene b. Shows the p orbitals which form the delocalized pi-bonding system in benzene c. Shape of the pi-electron clouds above and below the plane of the ring in benzene d. Electrostatic potential map of benzene

Figure Number: 07-01-03UN Title: Mythical Creatures and Resonance Hybrids Caption: Analogy between a resonance hybrid and a rhinoceros. Notes: The resonance contributors, like the unicorn and the dragon, are not real. Only the hybrid, like the rhinoceros, describes a real structure.

Figure Number: 07-01-04 Title: Cyclooctatetraene Caption: Structure and potential map of cyclooctatetraene. Notes: The pi electrons in the double bonds of cyclooctatetraene are not delocalized because the p orbitals do not overlap.

Figure Number: 07-06 Title: Resonance Energy Caption: Hess' Law diagram showing how the resonance energy of benzene is calculated. Notes: The difference between the heat released by hydrogenating three moles of C-C double bonds ("cyclohexatriene") and that released by hydrogenating one mole of benzene is called the resonance energy of benzene. Since less heat is released by hydrogenating benzene, benzene is more stable than "cyclohexatriene."

Figure Number: 07-07 Title: Resonance Energies of Oxyanions Caption: Resonance energies of conjugate bases of carboxylic acids are greater than the resonance energies of carboxylic acids. Notes: Since carboxylic acids and alcohols have similar stabilities whereas carboxylate ions have greater stabilities than alkoxide ions, carboxylic acids are stronger acids than alcohols. The oxyanion of a carboxylic acid is stabilized by resonance energy.

Figure Number: 07-07-07T01 Title: Table 7.1 Approximate pKa values Caption: Notes:

Figure Number: 07-08 Title: Figure 7.8 Caption: Pi bonding and antibonding orbitals in ethene. Notes: In-phase side-to-side overlap of the two p orbitals in the adjacent carbons in ethene results in a bonding pi molecular orbital, and out-of-phase overlap results in an antibonding MO.

Figure Number: 07-09 Title: Figure 7.9 Caption: Bonding and antibonding orbitals in 1,3-butadiene. Notes: Four p atomic orbitals on connected carbons overlap in four different ways to give four molecular orbitals. Half of the molecular orbitals are bonding, and the other half are antibonding.

Figure Number: 07-09-01UN Title: Symmetric and Fully Asymmetric Molecular Orbitals Caption: Symmetric and fully asymmetric (or antisymmetric) molecular orbitals with mirrors situated through their centers. Notes: Symmetric molecular orbitals are orbitals in which one half of the MO is a mirror image of the other half. Fully asymmetric MOs are orbitals in which the mirror image of one half of the MO has lobes with exactly opposite phases from the other half of the MO.

Figure Number: 07-09-02UN Title: 1,4-Pentadiene Caption: Bonding MOs of 1,4-pentadiene. Notes: 1,4-Pentadiene has two independent pi bonds separated from one another by a methylene carbon which does not contribute a p orbital to the system. For this reason neither of the p orbitals which form the one pi system can interact with either of the p orbitals which form the other pi system. The pi electrons cannot delocalize through the methylene carbon.

Figure Number: 07-10 Title: Figure 7.10 Caption: MOs of the allyl system and distribution of electrons in the allyl cation, anion, and radical. Notes: The allyl system contributes three atomic p orbitals to produce three MOs. The most stable bonding MO has to be symmetric, with all lobes interacting constructively with one another. MOs alter between symmetric and antisymmetric as they increase in energy. In order for the nonbonding (intermediate-energy) MO of the allyl system to be antisymmetric, it must have a node through the central carbon.

Figure Number: 07-11 Title: Figure 7.11 Caption: The six MOs of 1,3,5-hexatriene and electron occupancy of the neutral species. Notes: The six p orbitals on the six connected carbons in 1,3,5-hexatriene all interact, producing six MOs. Three of the MOs are bonding, and three of the MOs are antibonding. The number of nodes in the MOs increases as their energy increases, and MOs alter between being symmetric and antisymmetric as their energy increases.

Figure Number: 07-12 Title: Figure 7.12 Caption: Lowest energy MO of benzene and energies and electron occupancy of the six MOs in benzene. Notes: Benzene has MOs built from six p atomic orbitals. Half (three) of its MOs are bonding, and the other half are antibonding. Since benzene has an even number of MOs, it has no nonbonding MO. Systems with odd numbers of MOs have a nonbonding MO (ie., allyl). Since benzene can only accommodate three nodes before all of its contributing p orbitals interact destructively, only four different energy levels exist for benzene's six MOs (zero nodes, one node, two nodes, and three nodes). Therefore, four of benzene's MOs must occupy two energy levels in degenerate pairs.

Figure Number: 07-13 Title: Figure 7.13 Caption: The six MOs of benzene showing lobe phases and relative energies. Notes: As the energy of the MOs increases, the number of nodes increases and the net number of bonding interactions decreases. The mirror planes used to establish symmetric MOs and asymmetric MOs are the same as the nodal planes in benzene.

Figure Number: 07-14 Title: Figure 7.14 Caption: A comparison of the energy levels of the pi molecular orbitals of ethene, 1,3-butadiene, 1,3,5-hexatriene, and benzene. Notes: Note that benzene is more stable than 1,3,5-hexatriene. Benzene has more resonance energy than 1,3,5-hexatriene because of the additional connectivity of the pi system in benzene (which has one extra pair of connected carbons). The stabilization of 1,3,5-hexatriene over three isolated double bonds (i.e., three ethenes) is due to its resonance energy (ability of the double bonds to interact by being connected to the same pi system).

Figure Number: 07-07-07T01 Title: Table 7.1 Approximate pKa values Caption: Notes: