JEE Main · 2005 · 08 May 2005 · Offline · Compounds Containing Nitrogen

Basicity of an amine comes down to how freely the nitrogen lone pair is offered to a proton. In benzylamine the $-\mathrm{NH}{}_2$ hangs off an $s{p}^3$ $\mathrm{CH}{}_2$ group, insulated from the ring, so its lone pair is fully available and the compound is strongly basic. In aniline the lone pair is drawn into the benzene ring by resonance and so is less available; acetanilide locks the nitrogen into an amide and all but kills its basicity; and $p$-nitroaniline suffers both ring delocalisation and the electron-withdrawing nitro group. Benzylamine, with its unencumbered lone pair, is the most basic.