Pentalene is a polycyclic hydrocarbon composed of two fused cyclopentadiene rings. It has chemical formula . It is antiaromatic, because it has 4n π electrons where n is any integer. For this reason it dimerizes even at temperatures as low as −100 °C. The derivative 1,3,5-tri-tert-butylpentalene was synthesized in 1973. Because of the tert-butyl substituents this compound is thermally stable. Pentalenes can also be stabilized by benzannulation for example in the compounds benzopentalene and dibenzopentalene. It is prepared from reaction of dihydropentalene (pyrolysis of dicyclopentadiene or cyclooctatetraene) with n-butyllithium in solution and forms a stable salt.
See also
- Cyclooctatetraene
- Benzocyclobutadiene
- Acepentalene
- Butalene
- Heptalene
- Octalene