Mechanism of Electrophilic Substitution Reaction

The mechanism of electrophilic substitution reactions involves several steps that are discussed below:

• Generation of Electrophile: An electrophile is generated, by the interaction of a reagent or a catalyst with a precursor molecule. Common electrophiles are positively charged ions or species with partially positive charges.

• Attack of Electrophile: The electrophile attacks the electron-rich site in the substrate, a molecule containing a π – electron system, such as an aromatic ring. The attack occurs at a position with high electron density.

• Formation of a Sigma Complex (Intermediate): The attack of electrophile results in the formation of a sigma complex or an intermediate. This intermediate is often a positively charged species (carbocation), which may be stabilized by resonance or other factors.

• Rearrangement and Stabilization: Intermediate formed may undergo rearrangement to a more stable form depending on the specific reaction conditions and the nature of the substrate. Stabilization can occur through resonance, delocalization of charge, or other electronic effects.

• Loss of a Proton (or any group): The intermediate loses a proton (or any other group) to regain aromaticity or to achieve a more stable configuration. This step is essential for completing the substitution and maintaining the overall stability of the molecule.

Electrophilic Substitution is a type of organic reaction in which an electrophile replaces a functional group in a molecule. The functional group is generally a hydrogen atom. This reaction is commonly observed in aromatic compounds, where the aromaticity of the ring is maintained. Some of the common examples are Nitration, Halogenation, Sulfonation, etc.

In this article, we will learn about Electrophilic substitution reactions, its example, its mechanisms, their types, and the difference between electrophilic and nucleophilic substitution reactions.