MHTCET 18 Apr 2026 Shift 1 Paper

Concept:Hofmann's exhaustive alkylation converts amines into quaternary ammonium salts by repeated alkylation with excess alkyl halide.Explanation:A primary amine, $\mathrm{RNH}_2$, has two hydrogen atoms on nitrogen that can be substituted.To form a tetraalkylammonium halide, $\left[\mathrm{RN}\left(\mathrm{R}'\right)_3\right]^{+}\mathrm{X}^{-}$, three moles of alkyl halide are required:$$\mathrm{RNH}_2 \xrightarrow{\mathrm{R'X}} \mathrm{RNHR'} \xrightarrow{\mathrm{R'X}} \mathrm{RN}\left(\mathrm{R'}\right)_2 \xrightarrow{\mathrm{R'X}} \left[\mathrm{RN}\left(\mathrm{R'}\right)_3\right]^{+}\mathrm{X}^{-}$$Therefore, heating two moles of alkyl halide with one mole of primary amine gives only a tertiary amine, not a quaternary ammonium salt.So statement B is incorrect.Statement A is correct because quaternary ammonium salts are obtained.Statement C is correct because the product depends on the amount of alkyl halide used.Statement D is correct because $\mathrm{NaHCO}_3$ neutralises the acid formed during the reaction.Answer:Option B is NOT correct.