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.
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 penta(triphenylphosphine gold(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
- 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.
- IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Carbonium ion".
- Doo Wan Boo and Yuan T. Lee (1995), "Infrared spectroscopy of the molecular hydrogen solvated carbonium ions, CH+
2)n (n=1–6)". J. Chem. Phys. volume 103, page 520; doi:10.1063/1.470138
- L. I. Yeh, J. M. Price, and Y. T. Lee (1989), "Infrared spectroscopy of the pentacoordinated carbonium ion C
7". Journal of the American Chemical Society, volume 111, pages 5591-5604. doi:10.1021/ja00197a015
- George A. Olah (1998), "Onium Ions". John Wiley & Sons, 509 pages. ISBN 9780471148777
- 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
- Office of Energy Efficiency and Renewable Energy, U.S. DOE (2006). "Energy Bandwidth for Petroleum Refining Processes"