Hexaphenylbenzene

Preparation

It is prepared by heating tetraphenylcyclopentadienone and diphenylacetylene in benzophenone or other high-temperature solvent. The reaction proceeds via a Diels–Alder reaction to give the hexaphenyldienone, which then eliminates carbon monoxide.

:[[Image:HexaphenylbenzeneCheletropic.png|500px|Hexaphenylbenzene synthesis]]

Together with 1,2,3,4-tetraphenylnaphthalene, hexaphenylbenzene forms by the chromium-catalyzed oligomerization of diphenylacetylene. It may also be prepared by the dicobalt octacarbonyl-catalyzed alkyne trimerisation of diphenylacetylene. :[[Image:Diphenylacetylene cyclotrimerization.png|500px|Diphenylacetylene cyclotrimerization using dicobalt octacarbonyl]]

Structure

The stable conformation of this molecule has the phenyl rings rotated out of the plane of the central benzene ring. The molecule adopts a propeller-like conformation in which the phenyl rings are rotated about 65°, while in the gas phase, they are perpendicular with some slight oscillations.

References

References

1. Varun Vij, Vandana Bhalla, and Manoj Kumar. (2016). "Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold". Chemical Reviews.
2. Louis Fieser. "Hexaphenylbenzene". Organic Syntheses.
3. W. Herwig, W. Metlesics, H. Zeiss. (1959). "π-Complexes of the Transition Metals. X. Acetylenic π-Complexes of Chromium in Organic Synthesis". J. Am. Chem. Soc..
4. (February 2022). ["The crystal structure of a modification of hexaphenylbenzene"](http://journals.iucr.org/b/issues/1968/10/00/a06258/a06258.pdf }}{{Dead link). Acta Crystallographica Section B.
5. Gust, D.. (1977). "Restricted Rotation in Hexaarylbenzenes". [[J. Am. Chem. Soc.]].