Hcr

cr or

naphthalene

Notice that there are ten, not twelve, carbon atoms in total and that there are only eight hydrogen atoms, since the shared carbons have no attached hydrogen atoms. As a compound, naphthalene is a volatile solid whose vapor is toxic to some insects. It has found use as one form of "moth balls," the other being 1,4'dichlorobenzene.

Conceptually, there are two ways to fuse a third benzene ring to two carbons in naphthalene; one results in a linear arrangement for the centers (the "nuclei") of the rings while the other is a "branched" arrangement:

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anthracene phenarithrene

The resulting molecules, anthracene and phenanthrene, are PAH pollutants arising from incomplete combustion, especially of wood and coal. They are also released into the environment from the dumpsites of industrial plants that convert coal into gaseous fuel and from the refining of petroleum and shale. In rivers and lakes they are found mainly attached to sediments rather than dissolved in the water; both are subsequently partially incorporated into fresh-water mussels.

PROBLEM 12-1

Draw the full structural diagram for phenanthrene, showing all atoms and bonds explicitly.

PROBLEM 12-2

By determining their molecular formulas, show that the molecules below are not additional isomers of C j J i t | 0. ,

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