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Additional recommended knowledge
An arenium ion in organic chemistry is the cyclohexadienyl cation that appears as a reactive intermediate in electrophilic aromatic substitution. For historic reasons this complex is also called a Wheland intermediate or a sigma complex or σ-complex.
In the ion the positive charge is delocalized over 5 carbon atoms as a result of resonance:
The smallest arenium ion is protonated benzene C6H7+. The benzenium ion can be isolated as a stable compound when benzene is protonated by the carborane superacid H(CB11H(CH3)5Br6). The benzenium salt is crystalline with thermal stability up to 150°C. Bond lengths deduced from X-ray crystallography are consistent with a cyclohexadienyl cation structure.
More methods exist for the generation of stable arenium ions. In one study a methylene arenium ion is stabilized by metal complexation:
Categories: Cations | Reactive intermediates
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Arenium_ion". A list of authors is available in Wikipedia.|