Heterocyclic compound

In organic chemistry, a heterocyclic compound is a chemical compound that has a ring of atoms (it is a cyclic compound), and at least one atom in the ring is not carbon. The ring is called a heterocycle, and the non-carbon atoms are called heteroatoms.

Example heterocycle families

Class	Ring size	Heteroatom(s)	Example	Example structure
Epoxides	3	1 oxygen	Propylene oxide
Monosaccharides	5 (furanose) or 6 (pyranose)	1 oxygen	Glucopyranose
Lactams	Any	1 nitrogen	Caprolactam
Crown ethers	Any	Oxygen, fixed ratio to carbon	18-crown-6
Penicillins	4 and 5, fused	1 nitrogen, 1 sulfur	Penicillin
Porphyrins	5, four rings	1 nitrogen per ring	Heme

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