Carbonium ion explained

In chemistry, a carbonium ion is any cation that has a pentacoordinated carbon atom.^[1] The name carbonium may also be used for the simplest member of the class, properly called methanium, where the carbon atom is covalently bonded to five hydrogen atoms.^{[2] [3] [4] [5]}

The next simplest carbonium ions after methanium have two carbon atoms. Ethynium, or protonated acetylene, and ethenium are usually classified in other families. The ethanium ion has been studied as an extremely rarefied gas by infrared spectroscopy.^[6] The isomers of octonium (protonated octane,) have been studied.^[7] The carbonium ion has a planar geometry.

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 pentakis(triphenylphosphinegold(I))methanium, produced by Schmidbauer and others.^[8]

Preparation

Carbonium ions can be obtained by treating alkanes with very strong acids.^[9] Industrially, they are formed in the refining of petroleum during primary thermal cracking (Haag-Dessau mechanism).^{[10] [11]}

See also

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

Notes and References

1. Stable carbocations. CXVIII. General concept and structure of carbocations based on differentiation of trivalent (classical) carbenium ions from three-center bound penta- or tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions . George Andrew Olah . George Andrew Olah . . 1972 . 94 . 3 . 808–820 . 10.1021/ja00758a020.
2. 10.1063/1.470138. Infrared spectroscopy of the molecular hydrogen solvated carbonium ions, (n = 1–6). The Journal of Chemical Physics. 103. 2. 520. 1995. Boo. Doo Wan. Lee. Yuan T. 1995JChPh.103..520B.
3. . 309 . 5738 . 1219–1222 . Understanding the Infrared Spectrum of Bare CH₅⁺ . O. . Asvany . P. . Kumar P . B. . Redlich . 2005 . I. . Hegemann . S. . Schlemmer . D. . Marx . 10.1126/science.1113729 . 15994376. 2005Sci...309.1219A . 28745636 . free .
4. Xiao-Gang Wang . Tucker Carrington Jr . Calculated rotation-bending energy levels of CH₅⁺ and a comparison with experiment . Journal of Chemical Physics . 2016 . 144 . 20 . 204304 . 10.1063/1.4948549 . 27250303 . 2016JChPh.144t4304W .
5. H. Schmiedt . Per Jensen . S. Schlemmer . Rotation-vibration motion of extremely flexible molecules - The molecular superrotor . Chemical Physics Letters . 2017 . 672 . 34–46 . 10.1016/j.cplett.2017.01.045. 2017CPL...672...34S . free .
6. 10.1021/ja00197a015. Infrared spectroscopy of the pentacoordinated carbonium ion . Journal of the American Chemical Society. 111. 15. 5597. 1989. Yeh. L. I. Price. J. M. Lee. Yuan T.
7. 10.1021/jp021724v. Isomers of Protonated Octane, . The Journal of Physical Chemistry A. 106. 47. 11653. 2002. Seitz. Christa. East. Allan L. L. 2002JPCA..10611653S.
8. Book: George A. Olah . 1998 . Onium Ions . John Wiley & Sons . 9780471148777.
9. 10.1351/pac200072122309. Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes. Pure and Applied Chemistry. 72. 12. 2309. 2000. Sommer. J. Jost. R. free.
10. Office of Energy Efficiency and Renewable Energy, U.S. DOE (2006). "Energy Bandwidth for Petroleum Refining Processes"
11. Kotrel. S.. Knözinger. H.. Gates. B.C.. April 2000. The Haag–Dessau mechanism of protolytic cracking of alkanes. Microporous and Mesoporous Materials. en. 35-36. 11–20. 10.1016/S1387-1811(99)00204-8.