Heterocyclics with 1 hetero atom other than

Heterocyclic compounds are organic ring structures (-cyclic) that include an atom or atoms other than carbon (hetero-) in the ring. Thus, although compounds such as benzene and cyclohexane form organic rings, they do not include atoms other than carbon, and therefore do not qualify as heterocyclic. The particular number of elements in the ring varies, with... 

Heterocyclic compoimds have ring structure(s) that, imlike isocyclic compounds, contain atoms of elements other than carbon (see Figure 2.1). There are millions of heterocyclic compoimds in existence, which can be divided into six groups, as defined by Beilstein (see Section 2.2 above) and as listed in Table 2.7. The groups are characterised by the number of noncarbon (= hetero ) atoms they contain. Commonly these are atoms of oxygen or nitrogen, which form stable cyclic combinations with carbon, especially in 5- and 6-membered rings. 

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