Prism
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| Surname | Prism | |||||||||
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| Molecular formula | C 6 H 6 | |||||||||
| Brief description |
colorless, highly explosive liquid |
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| Molar mass | 78.11 g mol −1 | |||||||||
| Physical state |
liquid |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Prisman or Ladenburg benzene , empirical formula C 6 H 6 , is another name for the compound tetracyclo [2.2.0.0 2.6 .0 3.5 ] hexane. The connection got its name from its prism structure.
The structure was originally designed by Albert Ladenburg for the benzene - molecule suggested but turned out to be wrong. The hydrocarbon prism, which corresponds to the structure proposed at the time, was synthesized for the first time in 1973.
Prisman is under strong ring tension and is 377 kJ / mol more energetic than benzene . Regardless, Prisman is metastable even at room temperature . Robert B. Woodward and Roald Hoffmann discovered what opposes the rearrangement of prismane to benzene: the maintenance of orbital symmetry ( Woodward-Hoffmann rules ). Hoffmann and Fukui Ken'ichi received the Nobel Prize in Chemistry in 1981 for this theory . By this time Woodward (Nobel Prize 1965) had already passed away. Woodward and Hoffmann described Prisman as an " angry tiger that is unable to break out of its paper cage. "
Prisman is a colorless, volatile and explosive liquid.
synthesis
Prisman as a valence isomer of benzene can be produced from benzene via photochemical conversions :
An alternative synthesis of Prisman is also based on Benzvalen ( 1 ). For this purpose, benzvalene is reacted with the compound 4-phenyl-1,2,4-triazoline-3,5-dione ( PTAD ), which is the most reactive known dienophile to date . The reaction is a step-wise Diels-Alder type of reaction, with a carbenium ion as a reactive intermediate. The adduct 2 is hydrolyzed in a basic medium and then reacted with copper (II) chloride . Neutralization with a strong base gives the crystalline azo compound 3 in 65% yield. Photolysis of 3 yields a diradical with elimination of nitrogen , which then cyclizes to give prism ( 4 ).
Individual evidence
- ↑ a b c Entry on Prisman. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ^ Siegfried Hauptmann : Organic Chemistry , 2nd Edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, pp. 266–267, ISBN 3-342-00280-8 .