:Calicene
{{short description|Chemical compound}}
{{Chembox
| ImageFile = Calicene.svg
| ImageSize = 200px
| PIN = 5-(Cycloprop-2-en-1-ylidene)cyclopenta-1,3-diene
| OtherNames = Triapentafulvalene
| Section1 = {{Chembox Identifiers
| CASNo = 6249-23-6
| PubChem = 12302244
| ChemSpiderID = 26537418
| SMILES = C1(C=CC=C1)=C2C=C2
| StdInChI= 1S/C8H6/c1-2-4-7(3-1)8-5-6-8/h1-6H
| StdInChIKey = ZXWMPJFQZJXFQN-UHFFFAOYSA-N
}}
| Section2 = {{Chembox Properties
| C=8|H=6
| Appearance =
| Density =
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| Section3 = {{Chembox Hazards
| MainHazards =
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Calicene or triapentafulvalene is a hydrocarbon of the fulvalene class with chemical formula C8H6, 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,{{cite journal | last = Schaad| first = L. J. | author2 = B. Andes Hess, Jr |title = Dewar Resonance Energy | journal = Chemical Reviews | year = 2001 | volume = 101 | issue = 5 | pages = 1465–1476 | doi = 10.1021/cr9903609 | pmid = 11710229 }} 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.{{cite journal | last = Oziminski | first = W. P. | author2 = M. Palusia |title = Capturing the elusive aromaticity of bicalicene | journal = Physical Chemistry Chemical Physics | year = 2013 | volume = 15 | issue = 9| pages = 3286–3293| doi = 10.1039/C2CP43426A | pmid = 23358331 |bibcode = 2013PCCP...15.3286O}}
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){{cite journal | last = Ratanadachanakin | first = Thawalrat | author2 = Collier, Willard E. R. |title = Aromaticity of a series of poly-2,7-[N]calicenes| journal = Maejo International Journal of Science and Technology | year = 2015 | volume = 9| issue = 1 | pages = 21–31|url = http://www.mijst.mju.ac.th/vol9/21-31.pdf }}
Despite several attempts to prepare it, the parent calicene has so far defied attempts at synthesis.{{Cite book|title=Houben-Weyl Methods of Organic Chemistry Vol. E 17d, 4th Edition Supplement: Carbocyclic Three-Membered Ring Compounds, Cyclopropenes, Author Index, Compound Index|last=de Meijere|first=Armin|publisher=Georg Thieme Verlag|year=2014|isbn=978-3131819741|location=Stuttgart|pages=2967}} However, 1,2,3,4,5,6-hexaphenylcalicene has been prepared and an experimental dipole moment of 6.3 D was measured.{{Cite journal|last1=Agranat|first1=Israel|last2=Bergmann|first2=Ernst D.|date=1965-01-01|title=Hexaphenyltriapentafulvalene|journal=Chemical Communications|language=en|issue=21|pages=512–513|doi=10.1039/C19650000512|issn=0009-241X}}
References
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Category:Polycyclic nonaromatic hydrocarbons
Category:Hypothetical chemical compounds
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