JEE Main · 2019 · 09 Jan 2019 · Shift 2 · Compounds Containing Nitrogen

Compare the four bases by how freely the nitrogen lone pair is offered. In $N$-methylaniline the lone pair is pulled into the benzene ring, leaving it the weakest base. Among the aliphatic amines the familiar aqueous-phase order holds: the secondary diethylamine is the strongest, primary ethylamine next, and trimethylamine -- crowded despite its three alkyl groups -- sits between the aromatic amine and ethylamine. So the increasing order is $N\text{-methylaniline}<\text{trimethylamine}<\text{ethylamine}<\text{diethylamine}$.