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Prismane is a polycyclic hydrocarbon with the chemical formula C6H6. It is an isomer of benzene, but it is far less stable than benzene. The carbon atoms of the prismane molecule are arranged in the shape of a six-atom triangular prism. The systematic name is tetracyclo[2.2.0.02,6.03,5]hexane. Albert Ladenburg proposed this structure for the compound now known as benzene. The compound was not synthesized in the laboratory until 1973.
Additional recommended knowledge
The discussion about the structure of benzene in the mid 18th century yielded several structures for the formula C6H6, which was accessible by combustion analysis. The first, proposed by Kekulé in 1867, later proved to be the right one. This structure inspired several others to come up with concurring structures; for example, Ladenburg with prismane, Dewar with Dewar benzene, and Koerner and Claus with claus benzene. Some of these structures could be synthesized in the following years. Prismane, like the other proposed structures for benzene, is still often cited in the literature, because it is part of the historical struggle toward understanding the mesomeric structures and resonance of benzene. Some computational chemists still research the differences among the possible isomers of C6H6.
The deviation of the carbon-carbon bond angle from 109° in a tetrahedron to 60° in a triangle leads to a high ring strain, similar to that of cyclopropane. Due to this ring strain, the bonds have a low bond energy and break at a low activation energy, which makes synthesis of the molecule difficult. The molecule in which all six hydrogens are substituted by methyl groups (hexamethylprismane) has a higher stability and was synthesized by rearrangement reactions in 1966.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Prismane". A list of authors is available in Wikipedia.|