Polycyclic and Heterocyclic Aromatic Compounds

This chapter describes the structures of polycyclic aromatic hydrocarbons. It shows that most polycyclic aromatic compounds consist of two or more benzenoid rings fused together but some contain non-benzenoid rings. The chapter also explicates the reactions of polycyclic aromatic compounds, noting some polycyclic aromatic compounds including benzopyrenes are carcinogenic. The chapter then moves to discuss the structures of aromatic heterocycles. It stresses that the most common heterocyclic compounds contain one or more of three heteroatoms (N, O, and S) in the ring, and may be saturated or unsaturated. The chemistry of saturated heterocycles is generally similar to that of their acyclic counterparts. Unsaturated heterocyclic compounds are numerous and many are based on five- and six-membered aromatic rings containing a heteroatom. Finally, it discusses the reactions of five-membered aromatic heterocycles: pyrrole, furan, and thiophene. It also reviews the reactions of pyridine and its derivatives as well as the synthesis of aromatic heterocycles.