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My favorite groups of shapes are cupolas. Are there hydrocarbons in the shape of these similar to how cubane is to a cube? If so how stable are they, and could you please give some general information about each one.

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They would be highly unstable due to the inverted tetrahedral geometry of the carbons in the top face. Generally, a polyhedron can form the basis of a stable hydrocarbon if it has at most 3 edges for each corner. A big caveat is that the hydrocarbon will distort the shape if the angle strain is too great. I found that out in my computational research on prismanes.

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    $\begingroup$ So one does exist, the diagonal cupola exists. $\endgroup$ – tox123 Apr 25 '15 at 20:39
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    $\begingroup$ Yes, that would be prismane $\endgroup$ – ron Apr 25 '15 at 23:07
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If one forgets about the correct mathematical notation for a moment:

  • a cupola is like a bowl
  • a bowl is a fragment of a spherical object

Molecules of this shape are found in the field of fullerenes (bucky balls).

One of the most simple bowl-shaped molecules is sumanene. If you like to play a bit with the structure, please fetch sumanene.cml from pastebin and open it in Avogadro.

structure of sumanene

The shape is more obvious in the following animation.

animation of sumanene

The structure of two extended bowl-shaped molecules has been published in J. Am. Chem. Soc., 2011, 133, 16319–16321 ( DOI), and although they are not true cupolas, you might find them interesting anyway.

I've uploaded the structures bowl-01.cml and bowl-02.cml as CML files.

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