The next simplest carbonium ions after methanium have two carbon atoms.
Ethynium, or protonated
acetyleneC2H+3, and
etheniumC2H+5 are usually classified in other families. The
ethanium ion C2H+7 has been studied as an extremely rarefied gas by infrared spectroscopy.[7] The isomers of octonium (protonated octane, C8H+19) have been studied.[8] 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 (
Ph3PAu)5C+, produced by Schmidbauer and others.[9]
Preparation
Carbonium ions can be obtained by treating
alkanes with very strong acids.[10] Industrially, they are formed in the refining of petroleum during primary thermal
cracking (Haag-Dessau mechanism).[11][12]
^
abGeorge 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- or tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions". J. Am. Chem. Soc.94 (3): 808–820.
doi:
10.1021/ja00758a020.
^Xiao-Gang Wang; Tucker Carrington Jr (2016). "Calculated rotation-bending energy levels of CH5+ and a comparison with experiment". Journal of Chemical Physics. 144 (20): 204304.
Bibcode:
2016JChPh.144t4304W.
doi:
10.1063/1.4948549.
PMID27250303.
^Yeh, L. I; Price, J. M; Lee, Yuan T (1989). "Infrared spectroscopy of the pentacoordinated carbonium ion C 2H+ 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 8H+ 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.
ISBN9780471148777.