describe the nucleophilic substitution reactions ofhalogenoalkanes with NaOH(aq); KCN in ethanol; NH3 in ethanol;AgNO3(aq) in ethanol

Nucleophilic substitution reactions of halogenoalkanes involve the replacement of a halogen atom in the halogenoalkane by a nucleophile. The nucleophile is a species that donates a pair of electrons to form a new covalent bond.

1. Reaction with NaOH(aq): In this reaction, the hydroxide ion (OH-) from sodium hydroxide acts as the nucleophile. It attacks the carbon atom bonded to the halogen in the halogenoalkane, resulting in the removal of the halogen and formation of an alcohol.

R-X + OH- -> R-OH + X-

Where R represents the alkyl group, X represents the halogen, and OH- is the hydroxide ion.

2. Reaction with KCN in ethanol: In this reaction, the cyanide ion (CN-) from potassium cyanide acts as the nucleophile. It attacks the carbon atom bonded to the halogen in the halogenoalkane, resulting in the removal of the halogen and formation of a nitrile.

R-X + CN- -> R-CN + X-

Where R represents the alkyl group, X represents the halogen, and CN- is the cyanide ion.

3. Reaction with NH3 in ethanol: In this reaction, the ammonia molecule (NH3) acts as the nucleophile. It attacks the carbon atom bonded to the halogen in the halogenoalkane, resulting in the removal of the halogen and formation of an amine.

R-X + NH3 -> R-NH2 + HX

Where R represents the alkyl group, X represents the halogen, and NH2 is the amine group.

4. Reaction with AgNO3(aq) in ethanol: This reaction is used to test for the presence of halogenoalkanes. The silver ion (Ag+) from silver nitrate reacts with the halogen in the halogenoalkane to form a precipitate of the corresponding silver halide.

R-X + AgNO3 -> R-OH + AgX

Where R represents the alkyl group, X represents the halogen, and AgX is the silver halide precipitate.