Preparation of amines: the six NCERT methodsऐमीनों का विरचन: NCERT की छह विधियाँPreparation of amines: the six NCERT methods
Class 12 Chemistry · Chapter 9 · interactive diagram
Parts and what they mean
- Reduction of nitro compounds (नाइट्रो यौगिकों का अपचयन) — H₂ with finely divided Ni, Pd or Pt, or metal + acid (Sn/HCl, Fe/HCl). Fe scrap + HCl is preferred: FeCl₂ formed is hydrolysed and releases HCl, so only a little acid is needed.
- Ammonolysis of alkyl halides (ऐल्किल हैलाइडों का अमोनी-अपघटन) — Nucleophilic substitution of X by –NH₂ (ethanolic NH₃, sealed tube, 373 K). Disadvantage: mixture of 1°, 2°, 3° amines and quaternary salt; large excess of NH₃ gives mainly 1°. Reactivity RI > RBr > RCl.
- Reduction of nitriles (नाइट्राइलों का अपचयन) — LiAlH₄ or catalytic hydrogenation gives a 1° amine with one carbon MORE than the halide used → ascent of the amine series.
- Reduction of amides (ऐमाइडों का अपचयन) — (i) LiAlH₄ (ii) H₂O: the C=O becomes CH₂, so the amine keeps all the carbons of the amide.
- Gabriel phthalimide (गैब्रिएल थैलिमाइड संश्लेषण) — Phthalimide + ethanolic KOH → potassium phthalimide; heat with R–X; alkaline hydrolysis → pure 1° amine. Aryl halides do not react with the phthalimide anion, so ArNH₂ cannot be made this way.
- Hoffmann bromamide (हॉफमान ब्रोमेमाइड निम्नीकरण) — Amide + Br₂ + aqueous/ethanolic NaOH: the alkyl/aryl group migrates from the carbonyl C to N; the amine has one carbon LESS than the amide.
Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake