SN2 Reaction Mechanism

S_N2 reaction mechanism proceeds through a concerted backside attack of a nucleophile upon an alkyl halide. The critical steps of the S_N2 reaction mechanism can be summarized as follows:

• Nucleophile Approach: Nucleophile approaches the electrophilic carbon from the back side, opposite to the leaving group.

• Simultaneous Bond Formation and Cleavage: Nucleophile attacks the carbon while the leaving group starts to leave. It forms a new bond with the carbon via a backside attack, and the leaving group detaches from the reaction center in a concerted fashion.

• Inversion of Configuration: The reaction leads to the inversion of configuration at the reaction center, especially in the case of a molecule with a chiral center.

Example of S_N2 Reaction Mechanism

An example of an S_N2 reaction mechanism is the reaction between methyl bromide and hydroxide ion. The reaction can be represented as follows:

CH₃Br + OH^– ——-> CH₃OH + Br^–

Mechanism of this reaction can be broken down into the following steps:

Nucleophile Approach: The hydroxide ion approaches the carbon atom of the methyl bromide from the back side, opposite to the leaving group (bromine atom). The reaction can be represented as follows:

CH₃Br + OH^– ——-> [CH₃Br-OH]^–

Simultaneous Bond Formation and Cleavage: The hydroxide ion attacks the carbon atom while the bromine atom starts to leave. This results in forming a new bond with the carbon via a backside attack, and the bromine atom detaches from the reaction center in a concerted fashion. The reaction can be represented as follows:

[CH₃Br-OH]^– ——-> CH₃OH + Br^–

Inversion of Configuration: The reaction leads to the inversion of configuration at the reaction center, as the hydroxide ion replaces the bromine atom on the opposite side of the carbon atom.

S_N2 also called Substitution Nucleophilic Bimolecular reaction mechanism is an essential process in organic chemistry. It involves a nucleophile attacking the central atom while a leaving group is simultaneously displaced. The “S_N” in S_N2 stands for “substitution nucleophilic,” and the “2” indicates that the rate-determining step is bimolecular.

In this article, we will look into the S_N2 reaction mechanism, its examples, energy diagrams, applications, etc.