Structure, Properties and Uses of Aluminium Chloride

Introduction

Aluminium chloride is used to make aluminium metal in industry,  also  it has a lot of functions in the chemical industry, especially  as  Lewis acid. Covalently bound solid aluminium chloride (AlCl3) has a low melting and boiling temperature.

Hans Christian Oersted, a Danish scientist and chemist, discovered aluminium chloride in 1825. 

Structure of  AlCl3 

At 400°C, the evaporation density of anhydrous aluminium chloride was discovered to be 133. Al2Cl6 is the formula based on this. Each aluminium atom links to three co-conjugated chlorine atoms, and one chlorine atom is connected by a cohesive bond in the composition formula of anhydrous aluminium chloride. Each aluminium atom is surrounded by chlorine atoms in a tetrahedral structure.

At roughly 800°C, the vapour density of anhydrous aluminium chloride drops as the temperature rises, and the formula becomes  AlCl3. This formula is frequently used to represent aluminium chloride. Due to the presence of cohesive bonds, anhydrous aluminium chloride combines with organic solvents such as alcohol, acetone, ether, and carbon tetrochloride and does not conduct electricity in the molten state.

Properties of Aluminium Chloride

The chemical and physical properties of aluminium chloride will be discussed further down.

AlCl3 Physical Properties

1)The melting and boiling points of aluminium chloride are quite low.

2) At 180°C, it reaches its pinnacle.

3) AlCl3  is a bad conductor of electricity in its molten state.

4) Aluminum chloride is white in colour, but it is frequently contaminated by iron trichloride, which turns it yellow.

5) Only at pressures more than 2.5 atm and temperatures greater than 190°C can it become liquid.

6)  AlCl3  Chemical Properties

7) Aluminium chloride is an extremely potent Lewis acid.

8) It’s a significant industrial catalyst.

9)  AlCl3  is a corrosive solid that is anhydrous, non-explosive, and non-flammable.

10)When it comes into touch with water or bases, it reacts aggressively.

Reactions with Aluminium Chloride

We’ll learn how AlCl3 reacts with different substances in this section. Aluminium chloride, in its anhydrous form, is a strong Lewis acid. This means that it can create Lewis acid-base adducts even with weak bases in nature. Mesitylene and benzophenone, for example. The following are some common reactions:

When chloride ions are present, AlCl3 can produce tetrachloroaluminate (AlCl4–).

In tetrahydrofuran, aluminium chloride can react with magnesium and calcium hydride to generate tetrahydridoaluminate.

The Reaction of Aluminium Chloride with Water Aluminium chloride is hygroscopic, meaning it can collect moisture from the air. Normally, this chemical combination emits fumes into wet air. When it comes into touch with water, it makes a hissing sound. Cl– ions are replaced with H2O molecules during the process, resulting in hexahydrate [Al(H2O)6]Cl3. The anhydrous condition of AlCl3 is lost, and when heat is applied, HCl also disappears, leaving aluminium hydroxide as the end product.

Al(OH)3 + 3HCl + 3H2O = Al(H2O)6Cl3

Aluminum oxide is generated from the hydroxide when the temperature is raised to around 400°C.

Al2O3 + 3H2O = 2Al(OH)3

The fact that AlCl3 aqueous solutions are ionic is one of their distinguishing features. They are good conductors of electricity as a result of this. They’re also acidic, which can cause partial Al3+ ion hydrolysis. An example of a reaction:

[Al(H2O)6]

(aq)+(aq)+(aq)+(aq)+(aq [Al(OH)(H2O)5] H+ + 2+(aq) (aq)

Aluminium salts containing the hydrated Al3+ ion are similar to aqueous aluminium chloride solutions. They also act in the same way. When it reacts with dilute sodium hydroxide, for example, it produces a thick Al(OH)3 precipitate.

3NaOH + AlCl3  = Al(OH)3 + 3NaCl

Uses of Aluminium Chloride (AlCl3)

Aluminium chloride is a versatile chemical molecule that has a variety of applications, including chemical reactions and synthesis. The usage of aluminium chloride are- 

• AlCl3 is primarily utilised as a catalyst in a variety of chemical processes. 
• It is widely utilised in both acylations and alkylations in Friedel-Crafts reactions. 
• It’s utilised in the process of making anthraquinone from phosgene and benzene.
• It’s also employed in light molecular weight hydrocarbon polymerization and isomerization procedures. 
• The manufacturing of dodecylbenzene for detergents is one of the most common examples.
• Aluminium chloride has a number of different uses, particularly in organic chemistry. 
• Hydrocarbon couplings and rearrangements are induced using aluminium chloride.
• Aluminium Chloride’s Industrial Applications (AlCl3)
• Rubber, paints, wood preservatives are also made with aluminium chloride.
• Pesticides and medications contain it.
• As a flux in the melting  process of aluminium.
• It’s a type of antiperspirant.
• Petrochemicals such as ethylbenzene and alkylbenzene are also made from it.

Conclusion

Anhydrous aluminium chloride should be kept away from water and bases with caution. Because of the intense heat of hydration, aluminium chloride can explode if it comes into touch with water. It also emits fumes into the atmosphere. During chemical reactions, protective equipment such as glasses, gloves, and face guards should be worn. This chemical component should be kept in a firmly sealed container that is kept dry.

When  AlCl3  comes into contact with moist air, it absorbs the moisture and becomes very acidic, turning into a sticky substance.Materials like stainless steel and rubber can be severely corroded by it. This chemical can irritate the skin, eyes, and respiratory tract if exposed for an extended period of time. Aluminium chloride has been discovered to be a neurotoxic in some investigations, capable of destroying nerve tissues and causing lasting harm.

Anhydrous aluminium chloride is made by heating dry chlorine metal or dry hydrochloric acid gas to a hot aluminium metal and then evaporating the vapour.

When dry chlorine gas is injected into a heated combination of alumina and coke, anhydrous aluminium chloride is produced. On a large scale, this method is used. To make hydrogen aluminium chloride, heat aluminium oxide, aluminium hydroxide, or aluminium metal in dilute hydro acid to make alumina chloride solution. Crystals of hydrogen alumina chloride are produced after washing. AlCl3 is its chemical formula.