Aluminium bromide

1. Aluminium Bromide

Aluminium bromide refers to the chemical compounds with the formula AlBr₃ and its hydrates. It is a colorless, hygroscopic solid that is used in various chemical reactions and applications.

Structure and Properties

Aluminium bromide exists in several forms, including the anhydrous form and various hydrates. The anhydrous form, AlBr₃, is a white or yellowish solid that is highly soluble in water and other polar solvents. It has a layered structure similar to that of aluminium chloride, with each aluminium atom surrounded by six bromine atoms in an octahedral geometry.

The compound is highly hygroscopic, meaning it readily absorbs moisture from the air, and it can form a variety of hydrates, such as AlBr₃·6H₂O. In its anhydrous form, aluminium bromide is a Lewis acid, which means it can accept electron pairs from Lewis bases.

Synthesis

Aluminium bromide can be synthesized by the direct reaction of elemental aluminium with bromine:

2 Al + 3 Br₂ → 2 AlBr₃

This reaction is highly exothermic and must be controlled to prevent the loss of bromine as a gas. The product is typically purified by sublimation.

Applications

Aluminium bromide is used as a catalyst in organic synthesis, particularly in the Friedel-Crafts alkylation and acylation reactions. These reactions are important for the formation of carbon-carbon bonds in the synthesis of aromatic compounds.

Safety and Handling

Aluminium bromide is corrosive and can cause burns upon contact with skin. It should be handled with care, using appropriate personal protective equipment such as gloves and goggles. In case of contact with skin or eyes, the affected area should be rinsed thoroughly with water.

Also see

• Aluminium chloride
• Bromine
• Friedel-Crafts reaction
• Lewis acid