Chlorination Of Nitrobenzene

Chlorination of Nitrobenzene:

The chlorination of nitrobenzene is an electrophilic substitution reaction, which involves the replacement of a hydrogen atom on the benzene ring with a chlorine atom. The reaction is typically carried out in the presence of a catalyst, such as ferric chloride (FeCl₃), and a chlorinating agent, such as chlorine gas (Cl₂).

Introduction to Electrophilic Substitution

Electrophilic substitution is a type of organic reaction where an electrophile (an electron-deficient species) replaces a leaving group on a molecule. In the case of aromatic compounds like nitrobenzene, the electrophile attacks the π-electron system of the ring, leading to the formation of a new bond.

Formation of the Electrophile: Chlorinium Ion

In the chlorination of nitrobenzene, the electrophile is the chlorinium ion (Cl⁺), which is generated in situ from chlorine gas (Cl₂) and a Lewis acid catalyst, such as ferric chloride (FeCl₃) or Anhydrous AlCl₃.

The chlorinium ion is a strong electrophile, which can attack the π-electron system of the benzene ring.

Directing Effect of the Nitro Group

In chlorination of nitrobenzene, the nitro group (-NO₂) is a meta-directing group, which means that it directs the incoming electrophile to the meta position (the position at adjacent to the nitro group) on the benzene ring. This is because the nitro group withdraws electron density from the ring, making the meta position more electron-deficient and more susceptible to electrophilic attack.

Meta-Substituted Product Formation

In Chlorination of nitrobenzene, when the chlorinium ion attacks the nitrobenzene molecule, it forms a σ-complex, which is a high-energy intermediate. The σ-complex then collapses to form the meta-substituted product, 3-chloronitrobenzene.

The reaction mechanism is as follows:

1. Formation of the chlorinium ion (Cl⁺)
2. Electrophilic attack by Cl⁺ on the nitrobenzene molecule, forming a σ-complex
3. Collapse of the σ-complex to form the meta-substituted product, 3-chloronitrobenzene

The resulting product, 3-chloronitrobenzene, is a meta-substituted compound, where the chlorine atom has replaced a hydrogen atom on the benzene ring.

Summary

In summary, the chlorination of nitrobenzene is an electrophilic substitution reaction that involves the formation of a chlorinium ion, which attacks the π-electron system of the benzene ring, leading to the formation of a meta-substituted product, 3-chloronitrobenzene. The nitro group directs the incoming electrophile to the meta position, resulting in the formation of a meta-substituted product.

General

Chlorination of Nitrobenzene