Section 16.16 Electrophilic Substitution Reactions of Naphthalene and Substituted Naphthalenes 657A synthesis employing a benzyne intermediate is a good way to prepare meta-amino-
substituted aryl ethers (see Problem 31). The amide ion preferentially attacks the meta
position because there is less steric hindrance at this position and the resulting negative
charge can be stabilized by the adjacent electron-withdrawing oxygen atom.
PROBLEM 31Starting with benzene, show how meta-aminoanisole could be prepared via a synthesis that
a. involves a benzyne intermediate b. does not involve a benzyne intermediatePROBLEM 32Give the products that would be obtained from the reaction of the following compounds
with sodium amide in liquid ammonia:a. b. c. d.16.15 Polycyclic Benzenoid Hydrocarbons
Polycyclic benzenoid hydrocarbons are compounds that contain two or more fused
benzene rings. Fused ringsshare two adjacent carbons—naphthalene has two fused
rings, anthracene and phenanthrene have three fused rings, and tetracene, triphenyl-
ene, pyrene, and chrysene have four fused rings. There are many polycyclic benzenoid
hydrocarbons with more than four fused rings.
Like benzene, all the larger polycyclic benzenoid hydrocarbons undergo elec-
trophilic substitution reactions. Some of these compounds are well-known carcino-
gens. The chemical reactions responsible for causing cancer and how you can predict
which compounds are carcinogenic were discussed in Section 12.8.
16.16 Electrophilic Substitution Reactions of
Naphthalene and Substituted Naphthalenes
Like benzene, naphthalene is an aromatic hydrocarbon. Naphthalene has three reso-
nance contributors.
resonance contributors of naphthalenenaphthalene anthracene phenanthrenetriphenylene pyrene chrysenetetraceneOHBrBrCH 3CH 3CH 2 CH 3BrCH 3Cl