Calicene
Calicene or triapentafulvalene is a hydrocarbon of the fulvalene class with chemical formula C8H6, composed of linked a cyclopentadiene ring and a cyclopropene ring.Properties
Very high resonance energy is predicted by Hückel method, however its resonance energy is not high.
The central double bond is polarized with a partial positive charge on the carbon atom of triangular ring and a partial negative charge on the carbon atom of pentagonal ring, in keeping with added Hückel's rule stability of rings containing 2 π electrons and 6 π electrons respectively. Calicene's dipole moment has been computed to be 4.66 D.
Several compounds that contains two or more calicene subunits are aromatic, such as trans-bicalicene or poly-2,7-calicenes
Despite several attempts to prepare it, the parent calicene has so far defied attempts at synthesis. However, 1,2,3,4,5,6-hexaphenylcalicene has been prepared and an experimental dipole moment of 6.3 D was measured.
