17. Aromaticity

(••) Molecule A is significantly more water soluble than molecule B. Justify this observation.

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     A                        B

If Kekulé's original hypothesis had been correct and benzene was really an equilibrium between two structures, how many distinct isomers would exist for 1,2-dichlorobenzene?

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(a) Draw the resonance forms of benzene, cyclobutadiene, and cyclooctatetraene, showing all the carbon and hydrogen atoms.

(b) Assuming that these molecules are all planar, show how the p orbitals on the sp2 hybrid carbon atoms form continuous rings of overlapping orbitals above and below the plane of the carbon atoms.

Using the information in Figure 16-2, calculate the values of ∆H° for the following reactions:

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