A nitrilium ion is a

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...

that has been

protonated In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), usually denoted by H+, to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Br� ...

, CNHsup>+, or

alkylated Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...

, CNR′sup>+.

Synthesis

Nitriles are only weakly basic and are poor nucleophiles, but they will attack very reactive electrophiles such as

carbocation Carbocation is a general term for ions with a positively charged carbon atom. In the present-day definition given by the IUPAC, a carbocation is any even-electron cation with significant partial positive charge on a carbon atom. They are further ...

s. Nitrilium salts can be prepared by reacting nitriles with trialkyloxonium salts. The nitrilium ions thus formed can then be reduced to secondary amines with

sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula (sometimes written as ). It is a white crystalline solid, usually encountered as an aqueous basic solution. Sodi ...

diglyme Diglyme, or bis(2-methoxyethyl) ether, is an organic compound with the chemical formula . It is a colorless liquid with a slight ether-like odor. It is a solvent with a high boiling point. It is the dimethyl ether of diethylene glycol. The name '' ...

. This is a convenient route to secondary amines of the form RCH₂—NH—R′.

As intermediates

Nitrilium ions are believed to be intermediates in the hydrolysis of nitriles, the

Beckmann rearrangement The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement reaction, rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successfully performed on ...

, the Friedel-Crafts

cyclization A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where ...

of amines to

isoquinolines Isoquinoline is an individual chemical specimen - a heterocyclic aromatic organic compound - as well as the name of a family of many thousands of natural plant alkaloids, any one of which might be referred to as "an isoquinoline". It is a struc ...

, the

Schmidt reaction In organic chemistry, the Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually an aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen. ...

with ketones, and the Ugi,

Ritter Ritter (German for "knight") is a designation used as a title of nobility in German-speaking areas. Traditionally it denotes the second-lowest rank within the nobility, standing above " Edler" and below "" (Baron). As with most titles and desig ...

Pinner Pinner is a suburb in the London Borough of Harrow, northwest London, England, northwest of Charing Cross, close to the border with Hillingdon, historically in the county of Middlesex. The population was 38,698 in 2021. Originally a mediaeval ...

and Passerini reactions.

References

{{organic-compound-stub Nitriles