# Armilenium

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> Source: https://en.wikipedia.org/wiki/Armilenium
> Source revision: 1255256273
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{{Chembox
<!-- Images -->
| ImageFile      = Armilenium.svg
| ImageSize      = 150px
| ImageAlt       = 
<!-- Names -->
| IUPACName      = 1,2,4a,5,6,8a-Hexahydro-1,2,5-methenonaphthalen-6-ylium
| OtherNames     = [3.5.3]Armilenium; 9-Tetracyclo[5.4.0.0<sup>4,5</sup>.0<sup>3,8</sup>]undeca-5,10-dienyl cation
<!-- Sections -->
| Section1       = {{Chembox Identifiers
| CASNo          = 41946-89-8
| CASNo_Ref = {{Cascite|changed|EPA}}
| PubChem        = 12662406
| SMILES         = C1=CC2C3C=CC4C2C4C3[CH+]1
| StdInChI=1S/C11H11/c1-2-7-6-4-5-9-10(7)11(9)8(6)3-1/h1-11H/q+1
| StdInChIKey=YHLLCJAAILLOIR-UHFFFAOYSA-N
  }}
| Section2       = {{Chembox Properties
| C=11 | H=11 | Formula_Charge = +
  }}
|Section8={{Chembox Related
| OtherCompounds = 
 }}
}}

'''Armilenium''' is a {{chem|C|11|H|11|+}} [carbocation](/source/carbocation) and was originally proposed as the first entirely organic [sandwich compound](/source/sandwich_compound). Named for its resemblance to an [armillary sphere](/source/armillary_sphere), NMR evidence for the carbocation was first described by Melvin J. Goldstein and Stanley A. Klein at [Cornell University](/source/Cornell_University) in 1973.<ref>{{cite journal| vauthors = Goldstein MJ, Kline SA |date=1973|title=A C<sub>11</sub>H<sub>11</sub> cation of unusual structure|journal=Journal of the American Chemical Society|volume=95|issue=3|pages=935–936|doi=10.1021/ja00784a058}}</ref><ref>{{cite book| vauthors = Tennant G |year=1973|chapter=Molecular rearrangements|title=Annual Reports on the Progress of Chemistry, Section B: Organic Chemistry|volume=70|publisher=The Chemical Society |page=221 |doi=10.1039/OC9737000206 |isbn=0-85186-061-3 }}</ref><ref>{{cite journal| vauthors = Hogeveen H, Kwant PW |date=1975|title=Pyramidal mono- and dications: Bridge between organic and organometallic chemistry|journal=Accounts of Chemical Research|volume=8|issue=12|pages=413–420|doi=10.1021/ar50096a004}}</ref><ref>{{cite journal| vauthors = Goldstein MJ, Tomoda S, Pressman EJ, Dodd JA |date=1981|title=The automerization of C<sub>11</sub>H<sub>11</sub> chlorides and the stability of their cations|journal=Journal of the American Chemical Society|volume=103|issue=21|pages=6530–6532|doi=10.1021/ja00411a059}}</ref><ref>{{cite book| vauthors = Ahlberg P, Jonäll G, Engdahl C |year=1983|chapter=Degenerate carbocation rearrangements| veditors = Gold V, Bethell D |title=Advancements in Physical Organic Chemistry|series=Advances in Physical Organic Chemistry|volume=19|publisher=Academic Press|pages=366–367|doi=10.1016/s0065-3160(08)60224-5|isbn=0-12-033519-0}}</ref> In subsequent [<sup>13</sup>C NMR](/source/Carbon-13_nuclear_magnetic_resonance) experiments by Goldstein and Joseph P. Dinnocenzo in 1984, the {{chem|C|11|H|11|+}} carbocation was generated under stable ion conditions at lower temperature and at higher magnetic field than previously possible.<ref>{{cite journal| vauthors = Goldstein MJ, Dinnocenzo JP |date=1984|title=Automerization mechanism and structure of the C<sub>11</sub>H<sub>11</sub> armilenyl cation|journal=Journal of the American Chemical Society|volume=106|issue=8|pages=2473–2475|doi=10.1021/ja00320a062}}</ref> These experiments revealed the carbocation to be fluxional. Fitting of the dynamic NMR process ruled out the sandwich species even as an intermediate in the 20-fold degenerate rearrangement of the carbocation.

==References==
{{Reflist}}

Category:Carbocations

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Adapted from the Wikipedia article [Armilenium](https://en.wikipedia.org/wiki/Armilenium) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Armilenium?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.