Abstract

Cyclopentadiene and dicyclopentadiene, which occur as byproducts in the steam cracking process in ethylene plants, are the major ingredients in the production of hydrocarbon resins, unsaturated polyester resins, elastomers, pesticides, flame retardants and a host of specialty chemicals. The versatility of cyclopentadiene as the building block in so many chemicals stems from the high reactivity of its conjugated double bonds. They react readily with dienophiles, compounds with ethylenic or acetylenic unsaturation, to give Diels-Alder adducts, with oxygen and halogen to give oxygenates and halide derivatives. Cyclopentadiene dimerizes readily, via the Diels-Alder mechanism, to dicyclopentadiene at ambient conditions. The dimerization is highly exothermic. Because of its reactivity, cyclopentadiene is normally available only in the stable dimer form. Pure cyclopentadiene can be produced in-situ by the thermal cracking of the dicyclopentadiene at a temperature near the normal boiling point of the dicyclopentadiene.