Dodecahedrane is a chemical compound, a hydrocarbon with formula , whose carbon atoms are arranged as the vertices (corners) of a regular dodecahedron. Each carbon is bound to three neighbouring carbon atoms and to a hydrogen atom. This compound is one of the three possible Platonic hydrocarbons, the other two being cubane and tetrahedrane.

Dodecahedrane does not occur in nature and has no significant uses. It was synthesized by Leo Paquette in 1982, primarily for the "aesthetically pleasing symmetry of the dodecahedral framework".

The molecule has perfect icosahedral (I<sub>h</sub>) symmetry, as evidenced by its proton NMR spectrum in which all hydrogen atoms appear at a single chemical shift of 3.38&nbsp;ppm. Unlike buckminsterfullerene, dodecahedrane has no delocalized electrons and hence has no aromaticity.

History

For over 30 years, several research groups actively pursued the total synthesis of dodecahedrane. A review article published in 1978 described the different strategies that existed up to then. the original low-yielding isomerization of parent pagodane to dodecahedrane is replaced by a longer but higher yielding sequence - which nevertheless still relies heavily on pagodane derivatives. In the scheme below, the divergence from the original happens after compound 16.

:thumb|left|800px|Optimized route to dodecahedrane

Derivatives

A variety of dodecahedrane derivatives have been synthesized and reported in the literature.

Hydrogen substitution

Substitution of all 20 hydrogens by fluorine atoms yields the relatively unstable perfluorododecahedrane C<sub>20</sub>F<sub>20</sub>, which was obtained in milligram quantities. Trace amounts of the analogous perchlorododecahedrane C<sub>20</sub>Cl<sub>20</sub> were obtained, among other partially chlorinated derivatives, by reacting dissolved in liquid chlorine under pressure at about 140&nbsp;°C and under intense light for five days. Complete replacement by heavier halogens seems increasingly difficult due to their larger size. Half or more of the hydrogen atoms can be substituted by hydroxyl groups to yield polyols, but the extreme compound C<sub>20</sub>(OH)<sub>20</sub> remained elusive as of 2006.

Annulated dodecahedrane structures have been proposed.

References

  • Paquette's dodecahedrane synthesis at SynArchive.com
  • 2D and 3D models of dodecahedrane and cuneane assemblies
  • Full text of Paquette's paper