title: Calicene
text: # Calicene
  
  Calicene or triapentafulvalene is a hydrocarbon of the fulvalene class with chemical formula $C_8H_6,$ composed of a cyclopentadiene ring and a cyclopropene ring linked by a double bond. Its name is derived from the Latin calix meaning "goblet", from its shape.
  
  ## Properties
  
  Very high resonance energy is predicted by the 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 (ring compound) or poly-2,7-[N]calicenes (chain compound)
  
  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.
  
  