When an amide is treated with bromine in an aqueous solution of sodium hydroxide, degradation of amide take place leading to the formation of primary amines.
R – CH2 – C(0) – NH2 + 4 NaOH + Br2 →R – CH2 – NH2 + Na2 CO3 + 2NaBr + 2H2O
Aromatic primary amines react with nitrous acid at low temperatures to form diazonium salts. This conversion of aromatic primary amines into diazonium salts is nown as diazotization.
(iii) Gabriel phthalimide synthesis
Gabriel phthalimide synthesis is a very useful method for the preparation of aliphatic primary amines. It involves the reaction of phthalimide with ethanolic potassium hydroxide to form potassium salt of phthalimide. The product is further heated with alkyl halide, followed by alkaline hydrolysis to yield the corresponding amine.
(b) (i) (CH3)2NH is more basic than (CH3)3N in aqueos solutions because in(CH3)3N the lone pair of electrons on nitrogen atom is responsible forits basicity are quite hindered by the three methyl groups, hence are less available. Due to which it is less basic as compared to(CH3)2NH.
(ii)Aromatic diazonium salts are stable than aliphatic diazonium salts because the positive charge on nitrogen atom is stabilized by the resonance with attached phenyl group.
(b) Aniline can be distinguished from N,N-dimethyl aniline
by diazo couping reaction. Anline would react with benzene diazonium chloride to give yellow dye, where as N,N-dimethyl aniline won’t undergo this reaction.
(c) C2H5NH2 < C6H5NH2 < C6H5NHCH3
Ethylamine is soluble in water whereas aniline is not so pKb aniline is higher than that of ethylamine
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