Classification: 1° ($RNH_{2}$), 2° ($R_{2}NH$), 3° ($R_{3}N$); aniline = aromatic 1° amine

Gabriel synthesis gives ONLY 1° aliphatic amines — cannot make $ArNH_{2}$ (ArX no SN2), 2°, or 3° amines

Hoffmann bromamide gives FEWER carbons: $RCONH_{2}$ → $RNH_{2}$ (product has –1 carbon vs amide); carbonyl C lost as $Na_{2}CO_{3}$

Aqueous basicity order (most tested): 2° > 1° > 3° > $NH_{3}$ — solvation of conjugate acid governs this

Gas phase basicity order: 3° > 2° > 1° > $NH_{3}$ — +I effect only, no solvent

Aniline is a weak base (pKb ≈ 9.38) because lone pair is delocalized into benzene ring by resonance

EWG on aniline (e.g., p-$NO_{2}$) → weaker base; EDG (e.g., p-$OCH_{3}$) → stronger base

Carbylamine test ($CHCl_{3}$ + KOH → RNC, foul smell): specific for 1° amines ONLY

Hinsberg test: 1° sulfonamide soluble in NaOH; 2° sulfonamide insoluble; 3° no reaction

Diazotization: $ArNH_{2}$ + Na$NO_{2}$ + 2HCl at 0–5 °C → ArN_{2}^{+}$$Cl^{-} (must stay ≤5 °C)

Sandmeyer: $ArN_{2}^{+}$ + CuCl/HCl → ArCl; CuBr/HBr → ArBr; CuCN/KCN → ArCN

Gattermann: same products as Sandmeyer but uses Cu° (metallic copper powder), not CuX salt

Schiemann: $ArN_{2}^{+}$ + $HBF_{4}$ → ArN_{2}^{+}$$BF_{4}^{-} →($\Delta$) ArF — the ONLY reliable route to aryl fluorides

Azo coupling with phenol: requires alkaline medium (forms phenoxide); product orange-red

Azo coupling with aniline: requires weakly acidic medium (keeps –$NH_{2}$ free); product yellow

SMILES — Aniline: Nc1ccccc1; Fluorobenzene: Fc1ccccc1; p-Hydroxyazobenzene: Oc1ccc(/N=N/c2ccccc2)cc1