Gold(III) chloride

Gold(III) chloride, traditionally known as auric chloride, is a chemical compound of gold and chlorine. With the molecular formula AuCl₃, it is a yellow-orange solid. Gold(III) chloride is a common starting material in gold chemistry, particularly in the formation of gold-based catalysts and as a precursor to gold nanoparticles.

Properties

Gold(III) chloride is highly soluble in water, where it forms acidic solutions. It can also dissolve in ethanol and acetone. When heated, gold(III) chloride decomposes to gold(III) oxide and chlorine gas. In its solid form, it exists in two polymorphs: a stable form with a monoclinic crystal structure and a metastable form with an orthorhombic crystal structure.

Synthesis

Gold(III) chloride can be synthesized by reacting gold with chlorine at elevated temperatures. Another method involves the chlorination of gold in the presence of aqua regia (a mixture of nitric acid and hydrochloric acid), which dissolves gold to form chloroauric acid (HAuCl₄). The chloroauric acid can then be reduced to gold(III) chloride by heating or by adding a less noble metal such as sodium metabisulfite.

Applications

Gold(III) chloride is used in organic synthesis as a catalyst for reactions such as the cyclization of alkynes and the hydration of alkynes to ketones. It is also employed in the preparation of gold nanoparticles and in the decoration of ceramics and glass. In medicine, gold(III) chloride has been explored for its potential anti-cancer properties, though its use is limited due to its toxicity.

Safety

Gold(III) chloride is toxic if ingested, inhaled, or if it comes in contact with skin. It can cause severe irritation to the skin, eyes, and respiratory system. Appropriate safety measures, including the use of personal protective equipment, should be taken when handling this compound.

See also

• Gold compounds
• Chlorine
• Aqua regia
• Nanoparticle
• Organic synthesis