Amines — Important Questions

2,4,6-Tribromoaniline

Aniline is highly reactive towards electrophilic substitution. With bromine water, it undergoes tribromination to give 2,4,6-tribromoaniline as a white precipitate.

Reduction of nitrocompounds, Reduction of nitriles, Gabriel phthalimide synthesis, Hofmann degradation

All these methods can prepare primary amines: nitrocompound reduction gives RNH₂, nitrile reduction gives RCH₂NH₂, Gabriel synthesis gives pure primary amines, and Hofmann degradation converts amides to primary amines with one less carbon.

Carbylamine test

Carbylamine test is specific for primary amines. When heated with chloroform and KOH, primary amines give foul-smelling isocyanides (carbylamines). Secondary and tertiary amines do not give this test.

1° > 2° > 3°

Primary amines have the highest boiling point due to maximum hydrogen bonding (2 H atoms on N), secondary amines have intermediate boiling points (1 H atom on N), and tertiary amines have the lowest boiling points (no H on N, only van der Waals forces).