It can coordinate to positive ions such as ferrocene with the removal of a hydrogen ion, which gives it aromatic properties.  
It is prepared as a by-product during the fractional distillation of crude benzene from coal tar.  It can coordinate to positive ions such as ferrocene with the removal of a hydrogen ion, which gives it aromatic properties.  Its normal structure undergoes condensation reactions with ketones to give colored compounds called fulvenes, and it readily undergoes room temperature polymerization to form its dimer.  However, its most recognized use is as a reagent for creating cyclic compounds.  FTP, identify this compound with formula C5H6 used in the Diels-Alder reaction.
It is prepared as a by-product during the fractional distillation of crude benzene from coal tar.  
cyclopentadiene (accept early C5H6)