Question

Can carbon form a ring with 6 carbon atoms only, each one forming a double bond with its 2 adjacent carbon atoms?

Answer 1

Benzotriyne is a hypothetical chemical compound, an allotrope of carbon with molecular formula C6. The molecule is a ring of six carbon atoms, connected either by alternating triple and single bonds or by double bonds. It is, therefore, a potential member of the cyclocarbon family.

There have been a few attempts to synthesize benzotriyne, e.g. by pyrolysis of mellitic anhydride, but without success (as of 2011).

Recent investigations have concluded that benzotriyne is unlikely to exist due to the large angle strain. A likely alternative would be a cyclical cumulene called cyclohexahexaene, which should itself be a metastable species.