Annulene
Annulenes are fully conjugated , monocyclic hydrocarbons of the general formula (CH) n , where n denotes the size of the ring and is placed in front of the abbreviation of the annulenes in square brackets. 1,3- cyclobutadiene would therefore be [4] annulene. This simplified nomenclature for the determination of monocyclic hydrocarbons was introduced by Franz Sondheimer after the first successful synthesis of an [18] annulenes (1,3,5,7,9,11,13,15,17-cyclooctadecanonaen). In the case of pure hydrocarbon compounds, the size of the ring is also suitable as a quantitative indication of the π electrons. According to the Hückel rule, this is one of the decisive criteria for assessing the aromaticity of a conjugated ring system. [10] Annulene, however, is not aromatic despite compliance with this rule, since steric hindrance prevents the formation of a planar geometry. There are also several cis - trans isomers of this compound .
Web links
- Entry to annulenes . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.A00368 Version: 2.3.3.
- Overview of different annulenes
- Cristina Gelliniemail, Pier Remigio Salvi: Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States. In: Symmetry 2010, 2 (4), 1846-1924. doi : 10.3390 / sym2041846
- Structure of [14] Annulen and [18] Annulen ( Memento from July 25, 2011 in the Internet Archive )