MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

Hofmann's exhaustive alkylation is the process of converting an amine into a quaternary ammonium salt by treating it with an excess of alkyl halide. When a primary amine (RNH_2) is heated with an alkyl halide (RX), it undergoes successive nucleophilic substitution reactions: RNH_2 + RX R_2NH + HX (Secondary amine) R_2NH + RX R_3N + HX (Tertiary amine) R_3N + RX R_4N^+X^- (Quaternary ammonium salt) To convert one mole of a primary amine into a tetraalkyl ammonium halide, three moles of alkyl halide are required, not two. Therefore, the statement that two moles of alkyl halide form a tetraalkyl ammonium halide is incorrect. The reaction is typically carried out in the presence of a mild base like NaHCO _3 to neutralize the acid (HX) formed, which prevents the protonation of the amine and maintains its nucleophilicity. Depending on the stoichiometric ratio of the reactants, a mixture of secondary and tertiary amines can also be obtained. Answer: Two moles of alkylhalide when heated with one mole primary amine forms tetraalkyl ammonium halide.