Cyclocarbon


A cyclocarbon is a chemical compound consisting solely of a number n of carbon atoms covalently linked in a ring. Since the compounds are composed only of carbon atoms, they are allotropes of carbon. Possible bonding patterns include all double bonds or alternating single bonds and triple bonds.
As of 2020, the only cyclocarbon that has been synthesized is Cyclocarbon|cyclocarbon.

Cyclo6carbon

The six-carbon member of this family is also called benzotriyne.

Cyclo18carbon

The smallest cyclocarbon predicted to be thermodynamically stable is C18, with a computed strain energy of 72 kilocalories per mole. An IBM/Oxford team claimed to synthesize its molecules in solid state in 2019:
According to these IBM researchers, the synthesized cyclocarbon has alternating triple and single bonds, rather than being made of entirely of double bonds. This supposedly makes this molecule a semiconductor.