Fulvalene

Fulvalene (bicyclopentadienylidene) is the member of the fulvalene family with the molecular formula C₁₀H₈. It is of theoretical interest as one of the simplest non-benzenoid conjugated hydrocarbons. Fulvalene is an unstable isomer of the more common benzenoid aromatic compounds naphthalene and azulene. Fulvalene consists of two 5-membered rings, each with two double bonds, joined by yet a fifth double bond. It has D_2h symmetry.