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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2 Answers
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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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1$\begingroup$ So one does exist, the diagonal cupola exists. $\endgroup$– tox123Commented Apr 25, 2015 at 20:39
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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.
The shape is more obvious in the following animation.
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.
answered May 6, 2015 at 19:46