The Kolbe nitrile synthesis is a method for the preparation of
alkyl nitriles by reaction of the corresponding
alkyl halide
The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely us ...
with a metal
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
. A side product for this reaction is the formation of an
isonitrile because the cyanide ion is an
ambident nucleophile and according to
Kornblum's rule is capable of reacting with either carbon or nitrogen. The reaction is named after
Hermann Kolbe.
:
\underset + \underset -> \underset + \underset
The ratio in which both
isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
...
s form depends on the
solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
and the
reaction mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs.
A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage o ...
. With the application of alkali cyanides such as
sodium cyanide
Sodium cyanide is a poisonous compound with the formula Na C N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its h ...
and polar solvents the reaction type is an
SN2 reaction whereby the alkylhalide is attacked by the more nucleophilic carbon atom of the cyanide ion. This type of reaction together with
dimethyl sulfoxide
Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...
as a solvent is a convenient method for the synthesis of nitriles.
The use of DMSO was a major advancement in the development of this reaction, as it works for more
sterically
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...
hindered electrophilies (secondary and neopentyl halides) without rearrangement side-reactions.
See also
*
Rosenmund–von Braun reaction
The Rosenmund–von Braun synthesis is an organic reaction in which an aryl halide reacts with cuprous cyanide to yield an aryl nitrile.
:
The reaction was named after Karl Wilhelm Rosenmund who together with his Ph.D. student Erich Struck di ...
, a similar reaction for the synthesis of aromatic nitriles
References
{{DEFAULTSORT:Kolbe Nitrile Synthesis
Substitution reactions
Name reactions