91Ó°ÊÓ

The alkyl halide is an organic compound that is represented by the alkyl group bonded with any halogen atom (F, Cl, Br, I).

The halogen atoms are more electronegative than carbon. Therefore, it generates the electrophilic carbon at the position where the C-X bond.

The alkyl halide undergoes a nucleophilic substitution reaction in which a nucleophile attacks the carbon of the C-X bond (X is the halogen atom).

• If the attack of the incoming nucleophile occurs directly on the alkyl halide, it is a bimolecular substitution (S_N2) .
• If the attack of nucleophile occurs on the carbocation intermediate of alkyl halide, it is a unimolecular substitution.
• In the bimolecular substitution, the stereochemistry of the product gets changed, and in the unimolecular substitution, the stereochemistry remains the same.

The nucleophile in the nucleophilic reaction replaces the leaving group present in the substrate.

a.

Substituted product

So, in the given reaction, the alkyl halide is 1-chloro-4-methylpentane, and the leaving group is chloride in this compound. The ^-SH group attacks at the carbon-bearing chloride bond (C-Cl). Therefore, the product is formed by the elimination of chloride as shown below:

Nucleophilic substitution reaction

b.

Substituted product

So, in the given reaction, the alkyl halide is 1-chloropropane, and the leaving group is chloride in this compound. The ^-${\mathrm{OCH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3$group attacks at the carbon-bearing chloride bond (C-Cl). Therefore, the product is formed by

the elimination of chloride as shown below:

Nucleophilic substitution reaction

c.

Substituted product

So, in the given reaction, the alkyl halide is 1-chloroethane, and the leaving group is chloride in this compound. The ^-CN group attacks at the carbon-bearing chloride bond (C-Cl). Therefore, the product is formed by the elimination of chloride as shown below:

Nucleophilic substitution reaction

d.

Substituted product

So, in the given reaction, the alkyl halide is 1-chloroethane, and the leaving group is chloride in this compound. The ^-OCOCH₃ group attacks the carbon-bearing chloride bond (C-Cl). Therefore, the product is formed by the elimination of chloride as shown below:

Nucleophilic substitution reaction