Types of Halogenation Reactions

There are several types of halogenation reactions, which can be classified based on the nature of the substrate and the halogenating agent used. The main types of halogenation reactions include,

• Radical Halogenation
• Electrophilic Aromatic Substitution Halogenation

Let’s learn more about Halogenation Reaction in detail.

Radical Halogenation

Regioselectivity of Radical Halogenation of Cl₂ and Br₂ are shown in the image added below,

Both halogens (Chlorine and Bromine) follow the same pattern reacting more readily at the more substituted carbon. However, bromination is more selective.

Radical Halogenation is a type of halogenation reaction that involves the substitution of hydrogen atoms in an organic compound by halogen atoms through a free radical chain mechanism. This reaction is typical of alkanes and alkyl-substituted aromatics and requires energy input in the form of heat or light to initiate the reaction.

Halogenating agent is usually a halogen molecule, such as chlorine or bromine, which splits into two radicals upon heating, forming a couple of free radicals. The reaction proceeds through three steps: initiation, propagation, and termination. The reactivity of the halogens decreases in the order F₂ > Cl₂ > Br₂ > I₂, with fluorine being the most reactive and iodine being the least reactive.

Electrophilic Aromatic Substitution of Halogenation

Electrophilic aromatic halogenation is a type of electrophilic aromatic substitution reaction that involves the introduction of a halogen atom into an aromatic compound. This reaction typically follows three steps: activation of the electrophile by a Lewis acid catalyst, attack of the activated electrophile by the aromatic ring, and deprotonation to regenerate the aromatic ring.

Aromatic compounds like benzene undergo this reaction with halogens like chlorine, bromine, and iodine, typically requiring a Lewis acid catalyst such as AlCl₃, FeCl₃, FeBr₃, or ZnCl₂. The reactivity of the halogens in this reaction follows the order F₂ > Cl₂ > Br₂ > I₂, with fluorine being the most reactive and iodine being the least reactive. The mechanism of electrophilic aromatic substitution reactions, including halogenation, involves a two-step process, forming a sigma bond to the benzene ring followed by deprotonation to yield the substituted benzene ring.

Halogenation is a chemical process that involves adding halogen atoms into compounds. This reaction is common in organic chemistry and has diverse applications, from making drugs to flame retardants.

In this article, we will discuss about Definition of Halogenation, Types of Halogenation Reactions, Examples, and Others in detail.