Copper Dichloride

The chemical formula of copper chloride is CuCl2. Copper dichloride is an ionic, inorganic salt. It represents a yellowish-brown crystalline structure at room temperature in anhydrous form and blue-green when hydrated. The salt, therefore, is generally found in the hydrated form. Copper chloride has a wide range of uses in our day-to-day life. The compound involves the reaction between one divalent copper ion along with two chlorine ions. Both hydrous and anhydrated forms are naturally occurring as very rare minerals eriochalcite and tolbachite respectively.

Structure:

The anhydrous copper dichloride has a structure of cadmium iodide that shows distortion from octahedral geometry. In the hydrated form of copper dichloride, the copper attains a highly distorted octahedral structure in which the copper ion is surrounded by the water ligands and four chloride ions. Cupper dichloride is paramagnetic in structure. 

Properties of copper dichloride

Physical properties:

• Chemical formula: CuCl2
• Appearance: Yellowish-brown in anhydrous condition and blue-green in hydrated condition.
• Molar mass: 134.45 g/mol (anhydrous)
• Density: 3.386 g/cm3 (anhydrous)
• Melting point: 498 °C (anhydrous)
• Boiling point: 993°C (anhydrous)

Chemical properties:

• Hydrolysis: Precipitation of copper hydroxide occurs when copper chloride is reacted with a strong base-

CuCl2 + 2 NaOH → Cu(OH)2 + 2 NaCl

• Redox: During the redox reaction, the compound releases chlorine gas at a temperature near 1000°C.

2 CuCl2 → 2 CuCl + Cl2

Preparation of copper dichloride:

Industrial preparation of copper dichloride includes chlorination of copper at a temperature of 300-400°C which combines directly with chlorine gas to form copper dichloride in molten The reaction is highly exothermic in nature.

Cu(s) + Cl2(g) → CuCl2(l)

Sometimes, copper oxide is reacted with excess ammonium chloride at the same temperature to give copper dichloride as a product and ammonia and water as by-products.

CuO + 2NH4Cl → CuCl2 + 2NH3 + H2O

Sometimes, the copper metal which consists of some bases like hydroxide oxide or calcium carbonate can react with hydrochloric acid to give copper dichloride as the product. It should be noted that copper metal cannot react directly with hydrochloric acid.

After preparation it is necessary to purify the solution of copper dichloride, crystallization is done, as it contains a lot of impurities. 

A standard method takes the solution mixed with hot to dilute hydrochloric acid and causes the crystals to form by cooling in a Calcium chloride (CaCl2)-ice bath. 

There are some other methods that would give copper dichloride as a product from copper metal. Electrolysis of sodium chloride using copper electrodes can give blue-green foam which represents the hydrated form of copper dichloride. This is not a commonly used procedure because of the release of harmful chlorine gas in the reaction. The hydrated form of copper chloride can be dehydrated by adding hydrochloric acid to it. 

Uses:

• Co-catalyst in Wacker process:

One of the most important uses of copper dichloride is the use of the compound as a co-catalyst with palladium chloride in the Wacker process. The process includes the conversion of ethane to ethanol or acetaldehyde in the presence of water and air. In this reaction, PdCl2 is reduced to form Pd, and copper dichloride again restores back the PdCl2 by the process of oxidation. Again, the air present restores back CuCl to CuCl2.

1. C2H4 + PdCl2 + H2O → CH3CHO + Pd + 2 HCl
2. Pd + 2 CuCl2 → 2 CuCl + PdCl2
3. 4 CuCl + 4 HCl + O2 → 4 CuCl2 + 2 H2O

The overall process is:

2 C2H4 + O2 → 2 CH3CHO

• Catalyst in the production of chlorine

Copper(II) chloride is used as a catalyst in a variety of processes that produce chlorine by oxychlorination. The Deacon process takes place at about 400 to 450 °C in the presence of a copper chloride:

4 HCl + O2 → 2 Cl2 + 2 H2O

Copper dichloride is used as a catalyst in the process of chlorination of dichloroethane and vinyl chloride.

Conclusion:

Copper dichloride is an ionic, inorganic salt. It represents a yellowish-brown crystalline structure at room temperature in anhydrous form and blue-green when hydrated. The salt, therefore, is generally found in the hydrated form. Copper chloride has a wide range of uses in our day-to-day life. The compound involves the reaction between one divalent copper ion along with two chlorine ions. Both hydrous and anhydrous forms are naturally occurring as very rare minerals eriochalcite and tolbachite respectively. The anhydrous copper dichloride has a structure of cadmium iodide that shows distortion from octahedral geometry.