Ammonium cyanide

Uses

Ammonium cyanide is generally used in organic synthesis. Being unstable, it is not shipped or sold commercially.

Preparation

Ammonium cyanide is prepared in solution by bubbling hydrogen cyanide into aqueous ammonia at a low temperature

HCN + NH₃(aq) → NH₄CN(aq)

It may be prepared by the reaction of calcium cyanide and ammonium carbonate:

Ca(CN)₂ + (NH₄)₂CO₃ → 2 NH₄CN + CaCO₃

In dry state, ammonium cyanide is made by heating a mixture of potassium cyanide or potassium ferrocyanide with ammonium chloride and condensing the vapours into ammonium cyanide crystals:

KCN + NH₄Cl → NH₄CN + KCl

Reactions

Ammonium cyanide decomposes to ammonia and hydrogen cyanide, often forming a black polymer of hydrogen cyanide:

NH₄CN → NH₃ + HCN

It undergoes double decomposition reactions in solution with a number of metal salts.

It reacts with glyoxal, producing glycine (aminoacetic acid):

NH₄CN + (CHO)₂ → NH₂CH₂COOH + HCN

Reactions with ketones yield aminonitriles, as in the first step of the Strecker amino acid synthesis:

NH₄CN + CH₃COCH₃ → (CH₃)₂C(NH₂)CN + H₂O

Toxicity

The solid or its solution is highly toxic. Ingestion can cause death. Exposure to the solid can be harmful as it decomposes to highly toxic hydrogen cyanide and ammonia.

Chemical analysis

Elemental composition: H 9.15%, C 27.23%, N 63.55%.

Ammonium cyanide may be analyzed by heating the salt and trapping the decomposed products: hydrogen cyanide and ammonia in water at low temperatures. The aqueous solution is analyzed for cyanide ion by silver nitrate titrimetric method or an ion-selective electrode method, and ammonia is measured by titration or electrode technique.