Cyclopentadiene is a chemical compound with the formula C5H6. This colorless liquid organic chemical has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels-Alder reaction. This dimer "cracks" to give the monomer upon heating. The compound is the precursor to the popular cyclopentadienyl-ligand ('Cp') in cyclopentadienyl complexes in organometallic chemistry. Both cyclopentadiene and dicyclopentadiene can… (More on Cyclopentadiene)