In
chemistry, a carbonium ion is any
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
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 makes ...
atom.
The name carbonium may also be used for the simplest member of the class, properly called
methanium (), 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
Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pur ...
, 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 si ...
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
George Andrew Olah (born Oláh András György; May 22, 1927 – March 8, 2017) was a Hungarian-American chemist. His research involved the generation and reactivity of carbocations via superacids. For this research, Olah was awarded a Nobel Pr ...
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
alkane
In organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...
s 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
In chemistry and molecular physics, fluxional (or non-rigid) molecules are molecules that undergo dynamics such that some or all of their atoms interchange between symmetry-equivalent positions. Because virtually all molecules are fluxional in ...
*More carbonium ions called non-classical ion
Nonclassical carbocations are stabilized by charge delocalization from contributions of neighbouring or bonds, which can form bridged intermediates or transition states. Nonclassical ions have been extensively studied with the 2-norbornyl s ...
s are found in certain norbornyl
Norbornane (also known as bicyclo .2.1eptane) is an organic compound and a saturated hydrocarbon with chemical formula C7H12. It is a crystalline compound with a melting point of 88 °C. The carbon skeleton is derived from cyclohexane ring with a ...
systems
* Onium compounds
* Carbenium ion
References
{{Reflist
Reactive intermediates
Carbocations