Prismane 2563306 215332998 2008-05-27T19:09:50Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Chembox new | Name = Prismane | ImageFile = prismane structure.png <!-- | ImageSize = 100px --> | ImageName = Chemical structure of prismane | ImageFile1 = prismane-stick.png <!-- | ImageSize1 = 120px --> | ImageName1 = Chemical structure of prismane | ImageFile2 = prismane-CPK.png <!-- | ImageSize2 = 150px --> | ImageName2 = CPK model of prismane | IUPACName = Tetracyclo[2.2.0.0<sup>2,6</sup>.0<sup>3,5</sup>]hexane | Section1 = {{Chembox Identifiers | CASNo = 650-42-0 | SMILES = C12C3C1C4C2C34 }} | Section2 = {{Chembox Properties | Formula = {{carbon|6}}{{hydrogen|6}} | MolarMass = 78.1134 g/mol | Density = ? g/cm<sup>3</sup> | MeltingPt = | BoilingPt = °C }} }} '''Prismane''' is a polycyclic [[hydrocarbon]] with the [[chemical formula]] C<sub>6</sub>H<sub>6</sub>. 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 (geometry)|prism]]. The systematic name is tetracyclo[2.2.0.0<sup>2,6</sup>.0<sup>3,5</sup>]hexane. [[Albert Ladenburg]] proposed this structure for the compound now known as [[benzene]].<ref>{{cite journal | author=[[Albert Ladenburg| Ladenburg A.]]|title=.| journal= [[Chemische Berichte]]| volume= 2| pages= 140 | year=1869}}</ref> The compound was not synthesized in the laboratory until 1973.<ref>{{cite journal | author=Katz T. J., Acton N. | title= Synthesis of Prismane | journal= [[Journal of the American Chemical Society]] | year=1973 | volume=95 | pages=2738–2739|doi =10.1021/ja00789a084 }}</ref> ==History== The discussion about the structure of benzene in the mid 19th century yielded several structures for the formula C<sub>6</sub>H<sub>6</sub>, which was accessible by [[Combustion analysis|combustion&nbsp;analysis]]. The first, proposed by [[Friedrich August Kekulé von Stradonitz|Kekulé]] in 1867, later proved to be the right one. This structure inspired several others to come up with concurring structures; for example, [[Albert Ladenburg|Ladenburg]] with prismane, [[James Dewar|Dewar]] with [[Dewar benzene|Dewar&nbsp;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 C<sub>6</sub>H<sub>6</sub>.<ref>{{cite journal | author=UD Priyakumar, TC Dinadayalane, GN Sastry | title=A computational study of the valence isomers of benzene and their group V hetero analogs | journal= New J. Chem.| volume= 26| pages= 347–353 | year=2002|url =http://pubs.rsc.org/ej/NJ/2002/b109067d.pdf | doi=10.1039/b109067d }}</ref> ==Properties== The deviation of the carbon-carbon bond angle from 109° in a [[tetrahedron]] to 60° in a [[triangle]] leads to a high [[Ring strain|ring&nbsp;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 reaction]]s in 1966.<ref>{{cite journal | author= Lemal D. M., Lokensgard J. P.| title= Hexamethylprismane | journal= [[Journal of the American Chemical Society]] | year=1966 | volume=88 | pages=pp 5934–5935|doi =10.1021/ja00976a046 }}</ref> ==Synthesis== [[Image:Prismane-synthesis.png|620px|Synthesis of Prismane]] The synthesis starts from benzvalene ('''1''') and 4-phenyltriazolidone, which is a strong [[dienophile]]. The reaction is a stepwise [[Diels-Alder reaction|Diels-Alder like reaction]], forming a [[carbocation]] as intermediate. The adduct ('''2''') is then hydrolyzed under basic conditions and afterwards transformed into a [[copper(II) chloride]] derivative with acidic copper(II) chloride. Neutralized with a strong base, the [[azo]] compound ('''3''') could be crystallized with 65% yield. The last step is a [[photolysis]] of the azo compound. This photolysis leads to a [[biradical]] which forms prismane ('''4''') and [[nitrogen]] with a yield of less than 10%. ==References== {{reflist}} ==See also== * [[Prismane C8]], C<sub>8</sub> * [[Cubane]], C<sub>8</sub>H<sub>8</sub> * [[Fullerene]] ==External links== * [http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm Molecules with silly or unusual Names] [[Category:hydrocarbons]] [[de:Prisman]] [[nl:Prismaan]] [[ja:プリズマン]] [[zh:棱柱烷]]