Aliphatic amines have localized electron pairs on nitrogen and are far stronger bases than aryl amines where the nitrogen lone pair is delocalized into the benzene ring (+R effect). Among aliphatic amines in aqueous medium, diethylamine (N-ethylethanamine, $2^\circ$) is more basic than ethylamine (ethanamine, $1^\circ$) due to combined $+I$ and steric/solvation effects. Among aromatic amines, N-methylaniline has a $+I$ methyl group that enhances electron density on N relative to benzenamine (aniline). Thus: N-ethylethanamine > ethanamine > N-methylaniline > benzenamine.
ConceptAmine Basicity Trends
Amines in past papers
61 questions from this chapter have appeared across 27 exam years.
