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Q.Give two general methods for preparation of ammine. OR Convert aniline to benzoic acid.

Manipur CohsemCOHSEM Manipur Higher Secondary Board 2024Subjective· 3mImportance★★★★★
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This question offers a choice between general amine-preparation methods (primary) and converting aniline all the way to benzoic acid (the alternative). Both are answered below.

(Primary) — Two general methods for preparation of amines:

Method 1 — Reduction of nitro compounds: Aromatic/aliphatic nitro compounds are reduced (catalytic hydrogenation, H2/PdH_2/Pd, or with Fe/HClFe/HCl, Sn/HClSn/HCl) to primary amines:

R−NO2→H2/Pd or Fe/HClR−NH2R-NO_2 \xrightarrow{H_2/Pd\ \text{or}\ Fe/HCl} R-NH_2

Method 2 — Reduction of nitriles (or amides): Nitriles are reduced with LiAlH4LiAlH_4 or catalytic hydrogenation to give primary amines with one extra carbon compared to the halide they were made from:

R−C≡N→LiAlH4 or H2/NiR−CH2−NH2R-C\equiv N \xrightarrow{LiAlH_4\ \text{or}\ H_2/Ni} R-CH_2-NH_2

(A third well-known method is the Gabriel phthalimide synthesis, which gives pure primary amines free of secondary/tertiary contamination, via alkylation of potassium phthalimide followed by hydrolysis.)

OR — Convert aniline to benzoic acid:

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