Radical Bromination

What is Bromination?

Bromination is a process in which bromine is introduced into a molecule. The product formed after bromination displays completely different properties from the initial reactant molecule.

Based on the reactant molecule, bromination can occur in various ways.

• Bromination of alkane proceeds through a Free Radical Mechanism.
• Bromination of alkene proceeds through an Addition Mechanism.
• Bromination of aromatic compounds proceeds through an Electrophilic Substitution Mechanism.

Table of Content

• Free Radical Bromination
• Mechanism of Free Radical Bromination
• Significance of Bromination
• Frequently Asked Questions – FAQs

Free Radical Bromination

Free Radical Bromination is a process in which a free-radical chain mechanism introduces bromine into a molecule. It is shown by haloalkane or alkyl-substituted aromatic compounds under UV light.

It takes place in three steps.

Mechanism of Free Radical Bromination

Step 1: Initiation

Under ultraviolet rays, homolytic fission occurs between bromine atoms, resulting in the formation of two bromine radicals (Br. ).

Step 2: Propagation

Bromine radicals withdraw a proton from alkane to form an alkyl radical. Further, an alkyl radical removes bromine radical from the bromine molecule to form bromoalkane.

The above step occurs various times until termination takes place. These steps repeat many times until termination occurs.

Step 3: Termination

Termination takes place in three different ways.

• Two bromine radicals react with each other to form elemental bromine ( Br-Br)
• Bromine radical reacts with alkyl radical to form bromoalkane.
• Two alkyl radicals react with each other to form the corresponding alkane.

Significance of Bromination

• Bromination is used as a fire retardant, i.e. it prevents a substance from catching fire.
• It is used in synthesising chemicals used in sanitation and agriculture.
• It is used in the pharmaceutical industry.
• It is used as a building block for multiple syntheses.