JEE Main · 2021 · 26 Feb 2021 · Shift 2 · Compounds Containing Nitrogen

Phenyl methanamine is benzylamine, where the $\mathrm{C}{\mathrm{H}}_2$ group insulates the nitrogen lone pair from the ring, so the pair stays localised and the compound behaves as an ordinary aliphatic amine, the strongest base of the four. In the other three the nitrogen is bonded directly to the ring and its lone pair is delocalised into the $\pi$ system, which lowers basicity sharply. Among these three, methyl groups on nitrogen push electron density towards it and partly offset the delocalisation, so two methyl groups help more than one and unsubstituted aniline is the weakest. The order of basic strength is phenyl methanamine $>$ N,N-dimethylaniline $>$ N-methylaniline $>$ benzenamine.