In
chemistry, a carbonium ion is any
cation that has a
pentavalent carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
atom.
The name carbonium may also be used for the simplest member of the class, properly called
methanium
In chemistry, methanium is a complex positive ion with formula []+, namely a molecule with one carbon atom covalent bond, bonded to three hydrogen atoms and one hydrogen molecule, bearing a +1 electric charge. It is a superacid and one of the ...
(), where the five valences are filled with
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
atoms.
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
In chemistry, ethanium or protonated ethane is a highly reactive positive ion with formula . It can be described as a molecule of ethane () with one extra proton (hydrogen nucleus), that gives it a +1 electric charge.
Ethanium is one of the s ...
ion has been studied as an extremely rarefied gas by infrared spectroscopy.
The isomers of octonium (protonated octane, ) 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 , produced by Schmidbauer and others.
Preparation
Carbonium ions can be obtained by treating
alkanes with very strong acids.
Industrially, they are formed in the refining of petroleum during primary thermal
cracking (Haag-Dessau mechanism).
[Office of Energy Efficiency and Renewable Energy, U.S. DOE (2006)]
"Energy Bandwidth for Petroleum Refining Processes"
/ref>
See also
* Fluxional molecules
*More carbonium ions called non-classical ions are found in certain norbornyl systems
*Onium compounds
In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table), chalcogen (group 16), or halogen (group 17). The oldest-known onium ion, and the namesake ...
* Carbenium ion
References
{{Reflist
Reactive intermediates
Carbocations