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- Q642076 subject Q6262734.
- Q642076 subject Q7215729.
- Q642076 subject Q8343666.
- Q642076 abstract "An arenium ion in organic chemistry is a 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. The smallest arenium ion is benzenium ion C6H7+, which is protonated benzene. benzenium ionTwo hydrogen atoms bonded to one carbon lie in a plane perpendicular to the benzene ring. The arenium ion is no longer an aromatic species; however it is relatively stable due to delocalization: the positive charge is delocalized over 3 carbon atoms via the pi system, as depicted on the following resonance structures: Arenium Ion Resonance structuresA complexed electrophile can contribute to the stability of arenium ions. A 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.In one study a methylene arenium ion is stabilized by metal complexation:Methylene arenium ionIn this reaction sequence the R-Pd(II)-Br starting complex 1 stabilized by TMEDA is converted by dppe to metal complex 2. Electrophilic attack of methyl triflate forms methylene arenium ion 3 with (based on X-ray crystallography) positive charge located in aromatic para position and with the methylene group 6° out of the plane of the ring. Reaction first with water and then with triethylamine hydrolyzes the ether group.".
- Q642076 thumbnail Benzenium-3D-balls.png?width=300.
- Q642076 wikiPageWikiLink Q103230.
- Q642076 wikiPageWikiLink Q11295155.
- Q642076 wikiPageWikiLink Q11351.
- Q642076 wikiPageWikiLink Q139199.
- Q642076 wikiPageWikiLink Q161453.
- Q642076 wikiPageWikiLink Q2270.
- Q642076 wikiPageWikiLink Q36496.
- Q642076 wikiPageWikiLink Q417713.
- Q642076 wikiPageWikiLink Q4802699.
- Q642076 wikiPageWikiLink Q4818642.
- Q642076 wikiPageWikiLink Q5268094.
- Q642076 wikiPageWikiLink Q597833.
- Q642076 wikiPageWikiLink Q6262734.
- Q642076 wikiPageWikiLink Q7215729.
- Q642076 wikiPageWikiLink Q723069.
- Q642076 wikiPageWikiLink Q7485453.
- Q642076 wikiPageWikiLink Q826582.
- Q642076 wikiPageWikiLink Q8343666.
- Q642076 wikiPageWikiLink Q863695.
- Q642076 wikiPageWikiLink Q902363.
- Q642076 wikiPageWikiLink Q907614.
- Q642076 wikiPageWikiLink Q908086.
- Q642076 wikiPageWikiLink Q911365.
- Q642076 comment "An arenium ion in organic chemistry is a 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. The smallest arenium ion is benzenium ion C6H7+, which is protonated benzene. benzenium ionTwo hydrogen atoms bonded to one carbon lie in a plane perpendicular to the benzene ring.".
- Q642076 label "Arenium ion".
- Q642076 depiction Benzenium-3D-balls.png.