Pentals
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| Surname | Pentals | ||||||||||||
| Molecular formula | C 8 H 6 | ||||||||||||
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| Molar mass | 102.05 g mol −1 | ||||||||||||
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||
Pentalene is a bicyclic unsaturated hydrocarbon consisting of two fused cyclopentadiene rings. The molecule contains a double pentafulvene structural element . According to Hückel's rule , this compound with 8 π electrons is not to be counted among the aromatics , rather it is an anti- aromatic system that behaves like a non- mesomeric stabilized polyene .
presentation
A synthetic approach to pentalene and alkylpentalene derivatives is the cyclization of 6- (dialkylaminovinyl) pentafulvene ( 1 ). The primary cyclization product ( 2 ) is converted into the dihydropentalen derivative ( 3 ) by a sigmatropic rearrangement . The correspondingly substituted pentalen ( 4 ) is obtained from compound ( 3 ) via Hofmann degradation .
Multi-step synthesis of pentalenes
properties
Due to its high reactivity , pentalen ( 1 >) dimerizes to pentacyclo [8.6.0 2.9 .0 3.7 .0 11.15 ] hexadeca-3,5,7,11,13,15-hexaene even at very low temperatures ( 2 ) and can therefore only be detected by means of spectroscopy or capture reactions .
Dimerization of pentalenes
While simple alkyl pentalenes also dimerize very easily, tert-butyl- and phenyl-substituted pentalenes, benzopentalenes, and electronically stabilized pentalenes are relatively stable and easily accessible.
Individual evidence
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ↑ a b Hans-Jörg Lindner: Condensed carbocyclic-condensed systems . In: Heinz Kropf (Ed.): Houben-Weyl Methods of Organic Chemistry . Vol. V / 2c. Georg Thieme Verlag, Stuttgart, New York 1985, ISBN 3-9801412-1-7 , pp. 103 ff . ( limited preview in Google Book search).
- ↑ Hans Beyer: Textbook of organic chemistry . 18th edition. S. Hirzel Verlag, Stuttgart 1976, ISBN 3-7776-0342-2 , p. 575 f .
- ↑ Klaus Hafner: Pentalen - the solution to an old problem . In: News from chemistry, technology and the laboratory . Volume 28, Issue 4, 1980, doi : 10.1002 / nadc.19800280406 .