Nitriles

General formula of a nitrile, the functional group is marked in blue . The radical R is an organyl radical ( alkyl radical, aryl radical, alkylaryl radical, etc.). or - more rarely - an acyl radical.

Nitriles are a group of chemical compounds with the general formula R – C≡N. The functional group made up of carbon and triple bonded nitrogen is known as the nitrile or cyano group. The nitriles are formally derived from hydrocyanic acid (HCN) by exchanging the hydrogen atom for an organic residue. The isomers with the formula R – N≡C are called isonitriles .

Nitrile polymers are chemically very resistant and have rubber-like properties, which is why they are z. B. used for protective gloves .

nomenclature

Butyronitrile ,
according to IUPAC: butanenitrile ( blue marked C atom is part of the main chain),
formally also propanecarbonitrile ( blue marked C atom is part of the substituent)

If the nitrile is the functional group of the highest order, the ending "-nitrile" is added to the name of the starting compound, and it is named as "alkane nitrile". As always, the triple bonded carbon atom is included in the designation of the basic structure. Alternatively (analogous to -carboxylic acid ), the ending "-carbonitrile" can be used, here the carbon atom is not included in the basic structure.

If the nitrile function is not of the highest order in the molecule, the prefix “cyan” is used with the corresponding position designation. Here, too, the triple bonded carbon atom is not counted as part of the basic structure.

According to their relationship to the carboxylic acids (the nitrile carbon has the same oxidation state as the carboxyl carbon), many nitriles are trivially referred to as "carboxylonitriles", for example acetonitrile , propionitrile , butyronitrile or mandelonitrile .

Manufacturing

Nitriles are produced industrially by hydrocyanation ( addition of HCN to alkenes) and by catalytic oxidation of alkenes and ammonia with air.

On a laboratory scale nitriles may be prepared by reaction of alkali metal cyanides ( alkali metal - salts with hydrocyanic acid) alkyl halides are prepared ( Kolbe nitrile synthesis ). This creates the alkane nitrile and an alkali halide. Isonitriles occur as by-products . The conversion of methyl iodide with sodium cyanide to acetonitrile and sodium iodide is given as an example for this reaction:

${\displaystyle \mathrm {CH_{3}I+NaCN\longrightarrow CH_{3}CN+NaI} }$

Other options are the dehydration of aldoximes with z. B. phosphorus pentachloride PCl ₅ analogous to a Beckmann rearrangement , or the reaction of metal thiocyanates with carboxylic acids, known as Letts nitrile synthesis .

Preparation of aryl nitriles from quinones by reductive aromatization of silylated cyanohydrin intermediates

The production of aryl nitriles succeeds through the

• Sandmeyer reaction ( diazotization of aniline derivatives and reaction with copper (I) cyanide )
• Rosenmund-von Braun reaction (direct conversion of an aryl bromide with copper (I) cyanide )
• Reductive aromatization of silylated cyanohydrins (reaction of quinones with trimethylsilyl cyanide and subsequent aromatization with PBr ₃ )

Enantioselective synthesis of chiral nitriles

The enantioselective synthesis of nitriles is attracting increasing attention because sterically uniform chiral nitriles are used as drugs ( vildagliptin , saxagliptin ).

Reactions

Carboxylic acids can be produced by hydrolyzing nitriles .

Furthermore, an amine can be produced by reducing ( hydrogenating ) a nitrile .

use

A nitrile glove as used in medicine

Adiponitrile and acrylonitrile in particular are of practical importance as intermediate products in the manufacture of plastics .

One of the most important features of nitriles is that they can be easily introduced into a chemical synthesis and then converted into other functional groups (amino acids or amines). The process for the preparation of α- amino acids from aldehydes , in which nitriles occur as intermediate products, is known as the Strecker synthesis .

Acetonitrile is used as a solvent.

In medical examination gloves, those made of nitrile rubber are superior to those made of latex due to the lack of allergy risk . As a material for protective gloves, the good chemical resistance is particularly impressive.

See also

Isonitriles , R – N≡C, are isomers of nitriles and are used as starting materials in multi-component reactions ( Passerini reaction , Ugi reaction ).

Individual evidence

1. ^ Hans Beyer and Wolfgang Walter : Organische Chemie , S. Hirzel Verlag, Stuttgart, 22nd edition, 1991, ISBN 3-7776-0485-2 , pp. 266-269.
2. ↑ Entry on nitriles . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.N04151 Version: 2.3.3.
3. ↑ Entry on carbonitriles . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.C00838 Version: 2.3.3.
4. ↑ Florian Glöcklhofer, Markus Lunzer, Johannes Fröhlich: Facile Synthesis of Cyanoarenes from Quinones by Reductive Aromatization of Cyanohydrin Intermediates . In: Synlett . tape 26 , no. 07 , April 1, 2015, p. 950-952 , doi : 10.1055 / s-0034-1380150 .
5. ↑ Harald Gröger, Yasuhisa Asano: Cyanide-Free Enantioselective Catalytic Strategies for the Synthesis of Chiral Nitriles . In: The Journal of Organic Chemistry . doi : 10.1021 / acs.joc.9b02773 .