Molecule of the Week

Cyclopentadiene

April 21, 2008

Cyclopentadiene is a liquid with a low boiling point. It cannot be stored at room temperature because it spontaneously undergoes a Diels–Alder reaction with itself that forms the bridged dimer dicyclopentadiene. This reaction is reversible at elevated temperatures, so the most convenient way to obtain cyclopentadiene is to distill the commercially available dimer. Cyclopentadiene reacts with strong bases to form the cyclopentadienyl anion, which acts as a ligand in ferrocene and other “sandwich” complexes.