Aluminium Bromide(AlBr3) Properties (25 Quick Facts)

Aluminium bromide is a halogenated salt which is a hygroscopic molecule. Let us explore Aluminium bromide in detail.

Aluminium bromide is formed upon the reaction of hydrobromic acid and elemental Aluminium metal. It is also prepared for direct bromination of aluminium metal. Due to electronic deficiency at the aluminium center, it exists as a dimeric form, where 2 aluminium are connected via 3C-4e bonding.

The monomer has shape trigonal planar geometry where the Br-Al-Br bond angle is near about 120⁰ and central Aluminium sp² hybridized. Let us see some basic properties of Aluminium bromide like melting or boiling point, oxidation state, reaction tendency, density, and viscosity in the following part of the article.

1. Aluminium bromide IUPAC name

IUPAC (International Union of Pure and Applied Chemistry) gives the name for AlBr₃ as aluminium tribromide or aluminium(III) bromide.

2. Aluminium bromide chemical formula

AlBr₃ is the chemical formulation of monomeric Aluminium bromide, but the dimeric form is Al₂Cl₆ where Aluminium is known as Al and bromine is Br.

Screenshot 2022 11 11 113128 — **Dimeric Form of**
**Aluminium Bromide**

3. Aluminium bromide CAS number

Aluminium bromide has two different CAS numbers (up to the ten-digit numeric value given by Chemical Abstracts Service),

7727-15-3 (for anhydrous monomeric)
7784-11-4 (for hexahydrated form)

4. Aluminium bromide Chem Spider ID

22818 is the Chem Spider ID (given by the Royal Society of Chemistry) for Aluminium bromide.

5. Aluminium bromide chemical classification

Aluminium bromide can be classified into the following categories-

Aluminium bromide is an inorganic halogenated salt
Aluminium bromide is a hygroscopic molecule
Aluminium bromide is a strong electrolyte
Aluminium bromide is a good lewis acid
Aluminium bromide is a good catalyst
Aluminium bromide is a reference electrode

6. Aluminium bromide molar mass

Aluminium bromide has 266.69 g/mol as molar mass whereas the atomic mass of aluminium 26.98 and the atomic mass of 3 bromine are 79.04*3= 237.12.

7. Aluminium bromide color

Pure Aluminium bromide is colorless but impure molecule has color yellowish or even red-brownish due to being iron-containing.

8. Aluminium bromide viscosity

Solid Aluminium bromide has 0 viscosity as the property is only for fluid exerting the frictional force and the solid form is highly water soluble.

9. Aluminium bromide molar density

The molar density of the solid monomeric Aluminium bromide is 3.32 g/cm³.

10. Aluminium bromide melting point

The melting point for anhydrous Aluminium bromide is 97.5⁰ or 370.5K and for hexahydrate form, it is 93⁰C or 366K.

11. Aluminium bromide boiling point

Only the anhydrous form of Aluminium bromide has boiling point which is 255⁰C or 528K.

12. Aluminium bromide state at room temperature

Aluminium bromide exists in solid crystalline form at room temperature.

13. Aluminium bromide ionic bond

The bond between Aluminium and bromine is ionic because Aluminium ions easily polarized larger bromide ions due to their higher ionic potential as per Fajan’s rule. So, there will be a strong electrostatic force present between Aluminium and bromine which is ionic interaction.

14. Aluminium bromide ionic radius

The ionic radius of Aluminium and bromine are 184 pm and 185 pm respectively as they formed ion ionic bonds.

15. Aluminium bromide electron configurations

Electronic configurations are the arrangement of electrons by their number and position. Let us discuss the electronic configuration for AlBr₃.

The electronic configuration of Aluminium is [Ne]3s23p1
The electronic configuration of Bromine is [Ar] 3d104s24p5
The electronic configuration of a molecule or complex is unpredictable because its only for elements.

16. Aluminium bromide oxidation state

The oxidation state of the Aluminium in Aluminium bromide is +3 because it exists as Al³⁺ and the oxidation state of the bromine is -1 because it exists as bromide or Br^–.

17. Aluminium bromide acidity/alkaline

Aluminium bromide has an acidic character rather it is lewis acid, and it increases due to three electronegative bromine atoms pulling the electron density towards themselves and the Aluminium center becomes more positive and can accept more electron density.

18. Is Aluminium bromide odorless?

Aluminium bromide has a characteristic pungent smell like ammonia.

19. Is Aluminium bromide paramagnetic?

Paramagnetism is a property depending on the availability of the number of unpaired electrons. Let us see whether Aluminium bromide is paramagnetic or not.

Monomeric Aluminium bromide is paramagnetic due to 3 unpaired electrons over Aluminium but the dimeric form is diamagnetic due to the pair of all electrons. The magnetic susceptibility value of Aluminium bromide is −21*10⁻⁶ cm³/mol.

20. Aluminium bromide hydrates

Aluminium bromide is a hexahydrate molecule which means per Aluminium bromide contains 6 water molecules in its crystal which can represent AlBr₃.6H₂O.

21. Aluminium bromide crystal structure

The anhydrous form of Aluminium bromide has a monoclinic crystal structure in its lattice form, where the lattice constant, a = 0.7512 nm, b = 0.7091 nm, c =1.0289 nm, and α = 90⁰, β = 96.44⁰, and γ = 90⁰. Four

22. Aluminium bromide polarity and conductivity

Aluminium bromide is non-polar but conductive in nature and the supporting reasons are,

The molecule can be ionized in the Al³⁺ and Br^–. Both ions are highly conductive and have higher mobility due to higher charge density.
Aluminium bromide is rapidly soluble in water to get dissociated into ions.
The dipole moment of AlBr₃ flows from Al to Br.
Due to the trigonal planar geometry, which is a symmetric molecule, the resultant dipole moment will be 0 making the molecule non-polar AlBr₃ as well.

Screenshot 2022 11 11 113116 — Direction Of Dipole Moment of
aluminium bromide

23. Aluminium bromide reaction with acid

Being a lewis acid Aluminium bromide does not react with any acidic molecule but sometimes it reacts with a strong inorganic mineral acid like sulfuric acid.

H₂SO₄ + AlBr₃ = HBrO₃ + AlSO₄

24. Aluminium bromide reaction with base

Aluminium bromide can react with some lewis bases as it is strong lewis acid and form an adduct with that base. The electron deficiency is the main driving force for reacting Aluminium bromide with a suitable lewis base.

NH₃ + AlBr₃ = H₃N-AlBr₃

25. Aluminium bromide reaction with oxide

Aluminium bromide can react with superoxide and replace the Aluminium and form Aluminium oxide. Superoxide should be of some metal having higher electropositivity than Aluminium.

KO₂ + AlBr₃ = KBr + Al₂O₃

26. Aluminium bromide reaction with the metal

Aluminium bromide can react with Aluminium to form a dimeric form of the molecule or it can react with a complex of a transition metal having higher reduction potential.

AlBr₃ + COCl₂ → COBr₂ + AlCl₂Br

Conclusion

Aluminium bromide can be used as a catalyst for the Friedel-craft where the alkyl group should be incorporated in any aromatic ring. It is also used for any epoxide ring opening reaction promoted by lewis acid. Aluminium bromide can be disproportionate at room temperature so it always tries to exit in the dimeric form.