A Platonic hydrocarbon is a hydrocarbon (molecule) whose structure matches one of the five Platonic solids, with carbon atoms replacing its vertices, carbon–carbon bonds replacing its edges, and hydrogen atoms as needed.[page needed]
Not all Platonic solids have molecular hydrocarbon counterparts.
Tetrahedrane (C4H4) is a hypothetical compound. It has not yet been synthesized without substituents, but it is predicted to be kinetically stable in spite of its angle strain. Some stable derivatives, including tetra(tert-butyl)tetrahedrane (a hydrocarbon) and tetra(trimethylsilyl)tetrahedrane, have been produced.
Angle strain would make an octahedron be highly unstable due to inverted tetrahedral geometry at each vertex. There would also be no hydrogen atoms because four edges meet at each corner; thus, the hypothetical octahedrane molecule would be an allotrope of elemental carbon, C6, and not a hydrocarbon. The existence of octahedrane cannot be ruled out completely, although calculations have shown that it is unlikely.
Dodecahedrane (C20H20) has been synthesized, and has almost zero angle strain.
The tetravalency (4-connectedness) of carbon excludes an icosahedron since 5 edges meet at each vertex; pentacoordinate carbon, such as CH5+, is unlikely, although both icosahedral and octahedral structures have been observed in boron compounds.
With increasing numbers of carbon atoms in the frame, the geometry more closely approximates a sphere, and the space enclosed in the carbon "cage" increases. This trend continues with buckyballs or spherical fullerene (C60). Although not a Platonic hydrocarbon, fullerene has the shape of a truncated icosahedron, an Archimedean solid.
- Henning Hopf, Classics in Hydrocarbon Chemistry, Wiley VCH, 2000.[full citation needed]
- Lewars, Errol G. (2008). Modeling Marvels: Computational Anticipation of Novel molecules. Springer Science+Business Media. pp. 81–82. ISBN 978-1-4020-6972-7. doi:10.1007/978-1-4020-6973-4. Retrieved January 30, 2012.
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