An aromatic compound ‘A’ on treatment with aqueous ammonia and heating forms compound ‘B’ which on heating with Br2 and KOH forms a compound ‘C’ of molecular formula C6H7N. Write the structures and IUPAC names of compounds A, B and C
It is given that compound 'C' having the molecular formula, C6H7N is formed by heating compound 'B' with Br2 and KOH. This is a Hoffmann bromamide degradation reaction. Therefore, compound 'B' is an amide and compound 'C' is an amine. The only amine having the molecular formula, C6H7N is aniline, (C6H5NH2).
Therefore, compound 'B' (from which 'C' is formed) must be benzamide, (C6H5CONH2).
Further, benzamide is formed by heating compound 'A' with aqueous ammonia. Therefore, compound 'A' must be benzoic acid.
The given reactions can be explained with the help of the following equations:
Reduction of nitro compounds: Nitro compounds are reduced to amines by reduction with metals in an acidic medium or by passing them through hydrogen gas in the presence of finely divided nickel, palladium, or platinum.
Ammonolysis of alkyl halides: Alkyl benzyl halide undergoes a nucleophilic substitution reaction while reacting with an ethanolic solution of ammonia where the halogen atom is replaced by an amino group and this process of splitting of the C-X bond by an ammonia molecule is called ammonolysis.
Reduction of Nitriles: On reduction of nitriles with lithium or aluminum hydride or catalytic hydrogenation are used.
Reduction of amides: On reduction, the amides with lithium aluminum hydride yield amines.
Gabriel phthalimide synthesis: Gabriel synthesis is used to prepare primary amines. Phthalimidewhen treated with ethanolic potassium hydroxide, forms potassium salt of phthalimide which when heated with alkyl halide followed by alkaline hydrolysis leads to the formation of the corresponding primary amine.
Hoffmann bromamide degradation reaction: In the Hoffmann bromamide degradation reaction, the transfer of an alkyl or aryl group takes place from the carbonyl carbon of the amide to the nitrogen atom. The amine so formed, therefore, contains one carbon less than that present in the initial amine.
