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Nitriles

Nitriles, R–C≡N, have the carbon in the same oxidation state as carboxylic acids and are studied together with their derivatives. The C≡N triple bond is polar and linear; nucleophiles add to it and turn it into acids, amides, ketones, aldehydes or amines.

Examples of nitrile names: 4-methylpentanenitrile, (S)-2-methylhex-3-ynenitrile and butanedinitrile, where the functional group is within the main chain; trans-3-methylcyclohexanecarbonitrile and m-chlorobenzonitrile, where it cannot be; and 2-cyanoethyl cyanoacetate, where the nitrile is not the main function

Nomenclature

Model of acetonitrile with its bond lengths: C–H 1.09 Å, C–C 1.46 Å and C≡N 1.18 Å

Physical and Bond Properties

Protonation of an acid derivative R–CO–L at the carbonyl oxygen and resonance forms of the cation, with the positive charge on the oxygen, the carbon and the L group

Acid-Base Properties

Preparation of nitriles: nucleophilic substitution of haloalkanes with cyanide, Sandmeyer reaction of diazonium salts, cyanide addition to aldehydes and ketones (cyanohydrins), conjugate addition to α,β-unsaturated compounds and dehydration of aldoximes and amides

Preparation

Synthesis of acids via nitriles: RX + NaCN gives RCN and then RCOOH; aldehydes with HCN give cyanohydrins and hydroxy acids, and with HCN and NH₄Cl, aminonitriles and amino acids

Reactivity