In chemistry, carbonium ion is any cation that has a pentavalent carbon atom, 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.
The next simplest carbonium ions after methanium have two carbon atoms. Ethynium, or protonated acetylene C
3, and ethenium C
5 are usually classified in other families. The ethanium ion C
7 has been studied as an extremely rarefied gas by infrared spectroscopy. The isomers of octonium (protonated octane, C
19) have been studied. 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 and are now widely accepted.
A stable carbonium ion is the complex pentakis(triphenylphosphinegold(I))methanium (Ph
, produced by Schmidbauer and others.
- More carbonium ions called non-classical ions are found in certain norbornyl systems
- Onium compounds
- Carbenium ion
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- IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Carbonium ion". doi:10.1351/goldbook.C00839
- Boo, Doo Wan; Lee, Yuan T (1995). "Infrared spectroscopy of the molecular hydrogen solvated carbonium ions, CH+
n (n = 1–6)". The Journal of Chemical Physics. 103 (2): 520. Bibcode:1995JChPh.103..520B. doi:10.1063/1.470138.
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7". Journal of the American Chemical Society. 111 (15): 5597. doi:10.1021/ja00197a015.
- Seitz, Christa; East, Allan L. L (2002). "Isomers of Protonated Octane, C
19". The Journal of Physical Chemistry A. 106 (47): 11653. Bibcode:2002JPCA..10611653S. doi:10.1021/jp021724v.
- George A. Olah (1998). Onium Ions. John Wiley & Sons. ISBN 9780471148777.
- Sommer, J; Jost, R (2000). "Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes". Pure and Applied Chemistry. 72 (12): 2309. doi:10.1351/pac200072122309.
- Office of Energy Efficiency and Renewable Energy, U.S. DOE (2006). "Energy Bandwidth for Petroleum Refining Processes"