Chem Explorers

Unlocking the Power of Aluminium Bromide: Properties and Applications

Introduction to Aluminium Bromide

Aluminium bromide is a chemical compound that belongs to the family of inorganic halogenated salts. It is an important industrial compound, used in a range of application areas, including catalysts, organic synthesis, and polymerization.

This article provides an overview of the formation, chemical identity, and basic properties of aluminium bromide, with the aim of educating the reader.

Formation of Aluminium Bromide

The formation of aluminium bromide involves the reaction between hydrobromic acid and elemental aluminium metal, which releases hydrogen gas as a byproduct. Another method of forming aluminium bromide is through direct bromination of aluminium using bromine vapor.

This method leads to the formation of a mixture of aluminium tribromide and aluminum dibromide.

Dimeric and Monomeric forms

Aluminium bromide has two distinct forms, the dimeric form and monomeric form, both of which possess different structures and properties. The dimeric form is the most common and stable form of aluminium bromide, consisting of two AlBr3 molecules held together by 3C-4e bonding.

Its structure is trigonal planar with sp 2 hybridization. The monomeric form, on the other hand, consists of a single molecule and has a tetrahedral shape with sp 3 hybridization.

Basic Properties of Aluminium Bromide

The melting point of aluminium bromide is 97.8C. However, its boiling point is quite high and stands at 265C.

The density of aluminium bromide is also quite high, standing at around 3.01 g/cm3. Aluminium bromide is a viscous liquid with excellent solubility in organic solvents such as dichloromethane and diethyl ether.

Moreover, it has an oxidation state of III.

Chemical Identity of Aluminium Bromide

The IUPAC name of aluminium bromide is aluminium tribromide with a chemical formula of AlBr3. As mentioned earlier, it exists in dimeric form, which is a critical component in understanding the various properties of this compound.

Aluminium bromide has a CAS number of 7727-15-3, and its Chem Spider ID stands at 4294967295.

Chemical Classification

Aluminium bromide is classified as an inorganic halogenated salt, which is a hygroscopic molecule. Moreover, it’s a strong electrolyte, indicating its high level of ionic conductivity.

Aluminium bromide is an essential catalyst in organic synthesis, particularly in Friedel-Craft reactions.

Uses of Aluminium Bromide

Aluminium bromide has numerous uses in various industries. For instance, it is used as a catalyst in organic synthesis reactions since it increases the reactivity of the reactants and enhances the yield of molecules formed.

It is also used in Grignard reactions, whereby alkylmagnesium halide compounds react with carbonyl groups in aldehydes and ketones. Additionally, it is used in the synthesis of alkenes from alkyl halides via elimination reactions.


In conclusion, aluminium bromide is a widely used inorganic halogenated salt that is essential in several industrial chemical production processes. The compound has excellent properties, including high boiling point, high density, and strong ionic conductivity.

The dimeric and monomeric forms have distinct properties that make them applicable in different fields. With our understanding of this compound, we can safely and accurately apply it in various industries.

Physical Properties of Aluminium Bromide

Aluminium bromide is a solid, crystalline compound with a pungent odor that is colorless in appearance. It has a molar mass of 266.69 g/mol and a high viscosity.

The compound exists in two primary forms, anhydrous and hexahydrate forms. The molar density of anhydrous aluminum bromide is 3.01 g/cm3, while its hexahydrate form has a density of 2.31 g/cm3, and it is commonly found in a solid form.

It has a melting point of 97.8C and a boiling point of 265C. The hexahydrate form of Aluminium Bromide is a white crystalline powder that is highly soluble in water, albeit the crystals tend to become opaque upon exposure to air.

The ionic radius of aluminum ion is 55 pm, and the ionic bond in the compound is strong due to the difference in electronegativity between aluminium and bromine atoms. The electronic configuration of Aluminium is [Ne] 3s2 3p1, while bromine has an electronic configuration of [Ar] 3d10 4s2 4p5.

Chemical Properties of Aluminium Bromide

Aluminium bromide has numerous chemical properties that play a crucial role in its application and usage in various industries.

Oxidation State

Aluminium bromide has an oxidation state of 3+ because it loses three electrons to attain a noble gas configuration. Due to this, Aluminium Bromide readily reacts with nucleophiles to form Lewis acid-base adducts featuring a positively polarized aluminium center.


Aluminium Bromide is an acidic compound that reacts violently with water to form hydrobromic acid (HBr). It is also a strong lewis acid that can accept a pair of electrons from a Lewis base.

Paramagnetism, Hydrates, and Crystal Structure

The molecule of Aluminium Bromide is nonpolar with a dipole moment of zero, making it an extremely stable compound. Aluminium bromide exists as a dimer, which means that two aluminium bromide molecules bond together through bridging halides.

Each aluminium bromide atom exists in a trigonal planar configuration with a bond angle of 120 degrees. Moreover, Aluminium Bromide can form hexahydrate hydrates.

When crystallized, hexahydrate Aluminium Bromide occurs as a white powder that is very soluble in water. As such, its hydrates can exist in a paramagnetic state.

Polarity and Conductivity

Aluminium Bromide is a polar compound and reacts negatively with nonpolar molecules. Its polarity can be attributed to the uneven distribution of charge between an aluminium molecule and bromide ion.

Aluminium Bromide molecules are excellent conductors of electricity, mainly when used in the form of molten aluminum bromide.

Application of Aluminium Bromide

Aluminium Bromide is widely used for diverse applications in various industries. It’s primarily used in organic synthesis as a powerful Lewis acid catalyst, particularly in Friedel-Craft reactions.

It can also be used in the manufacture of dyes and pigments, refining crude oil, and synthesizing polymers. Furthermore, Aluminium Bromide’s hydrate has indispensable values in the microbiology industry.

Its ability to bind and precipitate nucleic acids has been extensively utilized as an alternative to toxic organic solvents also to selectively extract RNA from crude cellular debris.


Aluminium Bromide is a chemical compound with great industrial significance due to its unique physical and chemical properties. Its high boiling and melting point, molar density, polarity, conductivity, and other properties make it a versatile material in a broad range of industries.

Its use stems from industrial processes such as polymer synthesis to others within the biology circuit, where its hexahydrate’s ability to extract RNA from cells has made it indispensable.

Reactions of Aluminium Bromide

Aluminium Bromide exhibits varying reactions when combined with acids, bases, oxides, and metal, some of which are discussed below.

Reaction with Acids

When Aluminium bromide is dissolved in water, it readily undergoes hydrolysis, yielding hydrobromic acid, which is a strong acid. The hydrobromic acid is very corrosive and has a pungent smell that can cause severe respiratory problems.

Reaction with Base

When Aluminium Bromide reacts with a strong base such as NaOH, a displacement reaction occurs, liberating hydrogen. The chemical equation for this reaction is AlBr3 + 3 NaOH = Al(OH)3 + 3 NaBr + 3 H2O.

The reaction results in the formation of Aluminium Hydroxide, and Sodium Bromide, which is a byproduct of the reaction.

Reaction with Oxide

When Aluminium Bromide reacts with oxygen gas, it gets transformed into Aluminum Oxide, a white powdery substance that is highly heat resistant.

Reaction with Metal

Aluminium Bromide can react with metals to form complex salts. For instance, when Aluminium Bromide reacts with Lithium, a salt compound of Aluminium Lithium Bromide is formed.


Disproportionation is the chemical reaction where the same compound gets oxidized and reduced simultaneously. Aluminium Bromide exhibits this behavior, particularly when it is exposed to light or moisture.

In this reaction, AlBr3 gets converted to Br2, and Aluminum Hydroxide, releasing heat in the process. This reaction happens quickly and can be explosive.

Conclusion and Applications of Aluminium Bromide

Aluminium Bromide has many applications, primarily as a catalyst. Its versatility as a catalyst is seen in its reactions with Friedel-Craft Acylation and Alkylation reactions.

Friedel-Craft Acylation reactions occur when Aluminium Bromide is used to form acyl derivatives from arenes. On the other hand, Friedel-Craft Alkylation involves using Aluminium Bromide to link an alkyl group to an aromatic molecule.

Aluminium Bromide’s capability as a Lewis acid catalyst also extends to epoxide ring opening reactions, whereby it cleaves the epoxide ring and replaces it with another functional group. This reaction is used to synthesize various types of chemical compounds, such as drug molecules and organic materials.

Aluminium Bromide’s disproportionate properties have provided a unique opportunity in the purification of semiconductor materials. Here, the compound is used to purify Gallium and Indium used in semiconductor fabrication by disproportionation to provide high purity compounds for the industry.

In conclusion, Aluminium Bromide is an essential compound used in various industries to carry out diverse chemical processes. Aside from being an excellent catalyst, it also has high oxidative and reducing properties used in the fabrication of semiconductor materials.

Its properties of disproportionation and its unique Lewis Acid catalyst actions give it an edge over other catalysts in the industry. In summary, Aluminium Bromide is a highly versatile and valuable chemical compound that plays a significant role in several industries.

It has various physical and chemical properties that make it an excellent catalyst and a unique compound used in semiconductor fabrication. The article has discussed its formation, chemical identity, basic properties, physical and chemical properties as well as its reactions with other compounds.

Overall, Aluminium Bromide remains an important and indispensable element for several industries, and its applications in the areas of drug synthesis and semiconductor fabrication continue to prove invaluable.



What is Aluminium Bromide? Aluminium Bromide is an inorganic halogenated salt used primarily as a catalyst in various industries.

2. What are the physical properties of Aluminium Bromide?

The physical properties of Aluminium Bromide include high melting and boiling points, high densities, and pungent odor. 3.

What are the chemical properties of Aluminium Bromide? The chemical properties of Aluminum Bromide include high oxidation states and acidic/alkaline reactions.

4. What are the applications of Aluminium Bromide?

Aluminium Bromide has many applications, mainly as a catalyst in the synthesis of various compounds. 5.

What is the reaction of Aluminium Bromide with other compounds? Aluminium Bromide can undergo reactions with acids, bases, oxides, and metals, ultimately forming complex salts or undergoing disproportionation reactions.

Popular Posts