Copper(I) cyanide

Copper(I) cyanide is a chemical compound with the formula CuCN. This white solid occurs in two polymorphs; an amorphous form that is insoluble in water and a crystalline form that is slightly soluble. Copper(I) cyanide is used in copper plating and as a reagent in the preparation of nitriles and organic cyanides. It is notable for its role in the cyanide process of gold extraction.

Properties

Copper(I) cyanide has a molecular weight of 89.563 g/mol and a density of 2.9 g/cm^3. It decomposes upon heating, producing toxic fumes of cyanide and copper compounds. Its solubility in water is minimal, but it is soluble in solutions containing cyanide ions, forming complexes.

Synthesis

Copper(I) cyanide can be synthesized by the reaction of copper sulfate with sodium cyanide in the presence of an acid: \[ \text{CuSO}_4 + 2 \text{NaCN} + \text{H}_2\text{SO}_4 \rightarrow \text{CuCN} + \text{Na}_2\text{SO}_4 + \text{H}_2\text{O} + \text{HCN} \] This reaction proceeds via the formation of copper(II) cyanide, which is then reduced to copper(I) cyanide.

Applications

Copper Plating

Copper(I) cyanide is used in the electroplating industry for copper plating. It provides a smooth, adherent copper coating on various substrates, often used for decorative purposes or to prevent corrosion.

Organic Synthesis

In organic chemistry, copper(I) cyanide is a valuable reagent for the synthesis of nitriles and organic cyanides, serving as a source of the cyanide ion in various reactions.

Safety

Copper(I) cyanide is highly toxic, primarily due to its potential to release hydrogen cyanide gas, a potent inhibitor of cellular respiration. Handling requires appropriate safety precautions, including the use of personal protective equipment and adequate ventilation.

Environmental Impact

The use and disposal of copper(I) cyanide must be managed carefully to prevent environmental contamination. Its toxicity to aquatic life necessitates measures to prevent its release into water bodies.