Aqueous basicity of aliphatic amines: 2° > 1° > 3° > $NH_{3}$ — solvation of conjugate acid reverses 3° from gas-phase; aniline far weaker due to resonance delocalization of lone pair.

Gabriel phthalimide synthesis gives ONLY 1° aliphatic amines — cannot make $ArNH_{2}$ (no SN2 on ArX), 2° amines, or 3° amines; Hoffmann bromamide gives $RNH_{2}$ with ONE FEWER carbon than the amide.

Carbylamine test (foul smell) → 1° amines only; Hinsberg test: 1° soluble in NaOH, 2° insoluble, 3° no reaction — the two key amine identification tests for NEET.

Schiemann reaction ($HBF_{4}$ → ArF) is the ONLY reliable route to aryl fluorides; Sandmeyer uses CuX salts; Gattermann uses Cu° powder — confusing these three is a top NEET error.

Azo coupling with phenol needs ALKALINE medium (phenoxide); with aniline needs WEAKLY ACIDIC medium (free –$NH_{2}$) — diazotization must be kept at 0–5 °C or diazonium salt decomposes.