Fulvenes
Appearance
A fulvene is a hydrocarbon obtained by formally cross-conjugating one ring and Methylidene through a common exocyclic double bond.[clarification needed]
The name is derived from the similarly structured fulvenes, which lack one ring. Pentafulvene (2) is also called simply fulvene, the parent structure of this class.
Fulvenes are isomer of annulene