Amination

Overview

Ammonia substitutes bromide to form a primary amine; excess ammonia limits further alkylation.

Transformation

Bromoalkanes → Amines

Equation

R-Br + 2 NH3 -> R-NH2 + NH4Br

Reagents

excess NH3

Environment

ethanol, heat, sealed tube

Reaction class

nucleophilic substitution

Mechanism

nucleophilic substitution

Evidence level

textbook core

Scope and limitations

Scope

Preparation of primary amines from bromoalkanes using excess ammonia.

Limitations

The mechanism diagram uses a primary bromoalkane exemplar with excess ammonia to favour the primary amine. Further alkylation can give secondary/tertiary amines and quaternary ammonium salts if ammonia is not in excess.

Related reactions

• Bromination: Alcohols → Bromoalkanes

  Bromide and acid conditions convert alcohols into bromoalkanes.

• Hydrobromination: Alkenes → Bromoalkanes

  Addition of hydrogen bromide across an alkene can form a bromoalkane.

• Cyanation: Bromoalkanes → Nitriles

  Cyanide substitution forms a nitrile and extends the carbon chain by one carbon.

• Amination: Chloroalkanes → Amines

  Ammonia substitutes chloride to form a primary amine; excess ammonia limits further alkylation.

• Amination: Iodoalkanes → Amines

  Ammonia substitutes iodide to form a primary amine; excess ammonia limits further alkylation.

• Hydrolysis: Bromoalkanes → Alcohols

  The C-Br bond can be displaced by hydroxide to form an alcohol.

• Elimination: Bromoalkanes → Alkenes

  Base-promoted elimination removes HBr to form an alkene.

• Alkylation: Amines → Quaternary ammonium compounds

  Amines can be further alkylated to permanent cationic quaternary ammonium groups used in antimicrobial and ion-exchange materials.

• Reduction: Nitriles → Amines

  Nitriles can be reduced to primary amines, separating the amine feedstock route from later amide or materials chemistry.

• Free radical bromination: Alkanes → Bromoalkanes

  Photochemical bromination can convert alkanes into bromoalkanes.

• Acylation co reactant: Amines → N-substituted amides

  Amines are acylated by acyl chlorides to form N-substituted amides.

• Grignard formation: Bromoalkanes → Grignard reagents

  Bromoalkanes can react with magnesium in dry ether to form Grignard reagents.

• Weak base equilibrium: Amines → Aqueous alkylammonium ions

  Amines are weak bases in water and form alkylammonium and hydroxide ions.

• Salt formation: Amines → Amine salts

  Amines react with acids to form alkylammonium salts.

• Copper(II) complex formation: Amines → Copper-amine complexes

  Amines react with aqueous copper(II) ions and form a deep-blue complex in excess amine.

References

1. Pearson Edexcel Level 3 Advanced GCE in Chemistry specificationPearson Education Limited · Pearson qualifications · 2024

   Supports the textbook-core organic reaction routes used for displayed route and mechanism content.