Carbonium ion

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In chemistry, carbonium ion is any cation that has a pentavalent carbon atom,[1][2] The name carbonium may also be used for the simplest member of the class, properly called methanium (CH+
5), where the five valences are filled with hydrogen atoms.[3]

The next simplest carbonium ions after methanium have two carbons. Ethynium or protonated acetylene C
2H+
3 and ethenium H are usually classified in other families. The ethanium ion C
2H+
7 has been studied as an extremely rarefied gas by infrared spectroscopy.[4]

In older literature the name "carbonium ion" was used for what is today called carbenium. The current definitions were proposed by the chemist George Andrew Olah in 1972.[1] and are now widely accepted.

A stable carbonium ion is the complex penta(triphenylphosphine gold(I))methanium (Ph
3PAu)
5C+
, produced by Schmidbauer and others.[5]

Preparation

Carbonium ions can be obtained by treating alkanes with very strong acids.[6] Industrially, they are formed in the refining of petroleum during primary thermal cracking.[7]

See also

  • More carbonium ions called non-classical ions are found in certain norbornyl systems
  • Onium compounds
  • Carbenium ion

References

  1. ↑ 1.0 1.1 George Andrew Olah (1972). "Stable carbocations. CXVIII. General concept and structure of carbocations based on differentiation of trivalent (classical) carbenium ions from three-center bound penta- of tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions". J. Am. Chem. Soc. 94 (3): 808–820. doi:10.1021/ja00758a020. 
  2. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "Carbonium ion".
  3. ↑ Doo Wan Boo and Yuan T. Lee (1995), "Infrared spectroscopy of the molecular hydrogen solvated carbonium ions, CH+
    5    (H
    2    )n (n=1–6)". J. Chem. Phys. volume 103, page 520; doi:10.1063/1.470138
  4. ↑ L. I. Yeh, J. M. Price, and Y. T. Lee (1989), "Infrared spectroscopy of the pentacoordinated carbonium ion C
    2    H+
    7    ". Journal of the American Chemical Society, volume 111, pages 5591-5604. doi:10.1021/ja00197a015
  5. ↑ George A. Olah (1998), "Onium Ions". John Wiley & Sons, 509 pages. ISBN 9780471148777
  6. ↑ J. Sommer and R. Jost (2000), "Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes". Pure and Applied Chemistry, volume 72, pages 2309–2318. doi:10.1351/pac200072122309
  7. ↑ Office of Energy Efficiency and Renewable Energy, U.S. DOE (2006). "Energy Bandwidth for Petroleum Refining Processes"
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