# Aluminium Chloride

Aluminium Chloride $\left (AICI_{3}\right )$ is the primary compound of aluminium and chlorine. The solid aluminium chloride is covalently bonded and has a low boiling and melting point. The color of aluminium chloride is white, but often it is contaminated with iron trichloride, which makes it yellow in color.

It is often mentioned as a Lewis acid. Aluminum chloride cracks at mild temperatures and is an example of an inorganic compound. The aluminum chloride is mainly produced and largely consumed in the manufacture of aluminium metal and in chemical industry. In the chemical industry, it is used in many applications as a catalyst for Friedel-Crafts reactions, isomerization and polymerization reactions, and an antiperspirant.

## Aluminium Chloride Structure

Anhydrous

The aluminium chloride has three different structures based on the temperatures and the state: solid, liquid and gas. The solid $\left (AICI_{3}\right )$ aluminum chloride is a sheet-like layered cubic. In the melt, the aluminium trichloride presents as the dimer $\left (AI_{2}CI_{6} \right )$. This change is structure is due to the lower density of the liquid when compared to solid aluminium trichloride.

Hexahydrate

The hexahydrate has octahedral centers $\left [AI \left (H_{2}O \right )_{6} \right ]^{3+}$ and the chloride counterions.

### Aluminium Chloride Reactions

The anhydrous aluminium chloride is capable of forming mesitylene and benzophenone. It also forms tetra chloroaluminate $AICI_{4}^{-}$ with the chloride ions.

Reactions with Water

The $\left (AICI_{3} \right )$ is hygroscopic, fumes in moist air and hisses when mixed with water. The $CI^{-}$ ions are separated with water $H_{2}O$ molecules to form the hexahydrate $\left [AI \left (H^{2}O \right )_{6} \right ]CI_{3}$ and also turns into yellowish color from white.

$\left [AI\left (H^{2}O \right )_{6 } \right ]CI_{3} \rightarrow AI\left (OH \right )_{3} + 3 HCI + 3 H_{2}O$

While, heavily heating $\left ( 400^{\circ} C \right )$ aluminium oxide the aluminium hydroxide is formed:

$2 AI \left (OH \right )_{3} \rightarrow AI_{2}O_{3} + 3 H_{3}O$

Aqueous solutions of aluminium chloride

$\left [AI\left (H_{2}O\right )_{6} \right ]^{3+} \rightleftharpoons \left [AI\left (OH \right )\left (H_{2}O \right )_{5}\right ]^{2+} + H^{+}$

$AICI_{3} + 3 NaOH \rightarrow AI \left (OH \right )_{3} + 3 NaCl$

#### Practise This Question

Which are the starting materials for the preparation of