JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Haloalkanes and Haloarenes

The phthalimide anion is a nitrogen nucleophile whose negative charge is delocalised over two carbonyl groups, so it is not basic enough to cause elimination and attacks the primary benzylic carbon of benzyl bromide in an ${\mathrm{S}}_{\mathrm{N}}2$ displacement of bromide, giving N-benzylphthalimide. Alkaline hydrolysis then cleaves both amide linkages of the imide ring, releasing phthalate and setting the nitrogen free as a primary amine. Because the nitrogen was blocked by the imide while it was alkylated, only one alkyl group becomes attached to it, so A is benzylamine, ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{C}{\mathrm{H}}_2\mathrm{N}{\mathrm{H}}_2$.