Copper(II) complex formation

Overview

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

Transformation

Amines → Copper-amine complexes

Equation

[Cu(H2O)6]2+ + 4 RNH2 <-> [Cu(RNH2)4(H2O)2]2+ + 4 H2O

Reagents

aqueous Cu2+ ions

Environment

add amine, then use excess amine

Reaction class

ligand substitution

Mechanism

ligand substitution and acid-base chemistry

Evidence level

textbook core

Scope and limitations

Scope

Amines first act as bases to precipitate copper(II) hydroxide and in excess can act as ligands to form a deep-blue solution.

Limitations

The precise complex stoichiometry and observations can depend on the amine and concentration.

Related reactions

• Amination: Chloroalkanes → Amines

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

• Amination: Bromoalkanes → Amines

  Ammonia substitutes bromide 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.

• 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.

• Acylation co reactant: Amines → N-substituted amides

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

• 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.

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.