What are heterocyclic compounds?
◦ They are cyclic compounds in which carbon has one or more substituents that are neither hydrogen or another carbon atom.
◦ They are cyclic compounds in which two or more carbon rings are connected by C-C bonds (for example biphenyl).
◦ They are cyclic compounds in which carbon ring is connected to another ring not containing carbon atoms.
◦ They are cyclic compounds in which one or more atoms are not carbon atoms.
◦ They are cyclic compounds that can have more than one stable conformation.