ABSTRACT
Aromatic hydrocarbons and their unique chemistry were introduced in Chapter 21. ere is another class of aromatic compounds in which heteroatoms replace one or more of the ring carbons. ese compounds are collectively known as heterocycles or heterocyclic aromatic compounds, and they comprise a class of compounds so large that an entire course is easily built around their chemistry. Heterocycles are seen in several places in this book, including a brief introduction to their conformation in Section 8.9. e most common heterocycles include ve-and six-membered monocyclic derivatives that contain nitrogen, oxygen, or sulfur. ere are several important bicyclic derivatives that contain nitrogen. e use of heterocycles in medicine and industry is extensive. is chapter will expand the aromatic chemistry from Chapter 21 and introduce heterocyclic chemistry.
