Amines - Nitriles (A-Level Chemistry)

Nitriles

Nitriles

A nitrile is an organic compound consisting of an alkyl group with a cyanide group (-CN) attached.

The cyanide group consists of a carbon and a nitrogen atoms linked by a triple covalent bond.

The lone pair of electrons on the N atom in the cyanide groups gives nitriles nucleophilic properties.

Nitrile Reactivity

Amine Formation

Aliphatic amines can be synthesised by the reduction of nitriles.

Nitriles can be reduced in three ways:

  • Using LiAlHā‚„ – LiAlHā‚„ is a strong reducing agent. First, LiAlHā‚„ is added to a nitrile in dry ether or another non-aquous solvent. Some dilute acid is then added. The nitrile get reduced into a primary amine.
  • Using sodium metal – Nitriles can also be reduced to form a primary amine by reacting with sodium metal and ethanol.
  • Catalytic Hydrogenation – Nitriles can also be reduced to primary amines by reacting them with hydrogen gas in the presence of a metal catalyst such as nickel or platinum. High temperatures and pressures are needed.

Due to the high cost of LiAlHā‚„, catalytic hydrogenation is the preferred method in industry

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Carboxylic Acid Formation

Carboxylic acids can be formed by hydrolysis of nitriles.

The nitrile is made to react with hydrochloric acid under reflux to form a carboxylic acid and ammonium chloride salt.

The carboxylic acid can then be distilled off.

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