Carbon ring

Carbon rings are rings of carbon atoms. Rings of five and six carbons are by far the most common, as they allow bond angles close to the ideal angle of 109.5°. Rings of three and four are possible, but with bond angles of 60° and 90°, they have a larger ring strain and are unstable. Ring strain decreases with an increasing number of carbon atoms until cyclohexane, which is a six-membered ring. After cyclohexane, ring strain increases again until cyclotetradecane, with 14 carbon atoms. Ring strain starts to decrease again, but slowly; very large rings have little ring strain, as they are almost linear.

Compounds such as cycloalkenes or benzene, or the non-benzenoid aromatic tropone, have a single carbon ring; rings can also be joined, with some atoms being a part of more than one ring. Naphthalene is the simplest such multi-ringed hydrocarbon, having the structure of two fused benzene rings.