The standard route to aromatic amines: ArNO2 -> ArNH2. Reducing agents: (1) Sn/HCl — classical method, gives amine hydrochloride (add NaOH to free amine). (2) Fe/HCl — similar to Sn/HCl. (3) H2/Pd — catalytic hydrogenation (cleanest). (4) Zn dust/NH4Cl — in neutral medium. For selective reduction: (a) Zn/NH4Cl reduces -NO2 to -NHOH (hydroxylamine) at low temperature. (b) Na2S or (NH4)2S selectively reduces one -NO2 in dinitro compounds (e.g., m-dinitrobenzene -> m-nitroaniline). (c) LiAlH4 reduces nitro but also reduces other groups (not selective). Nitrile reduction: RCN + LiAlH4 or H2/Ni -> RCH2NH2 (primary amine, one extra carbon vs the parent acid).