InterviewSolution
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InterviewSolution
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(a) Give reasons : (i) Although-NH_(2) group is o/p directing in electrophilic substitution reactions, yet aniline, on nitration gives good yield of m-nitroaniline. (ii) (CH_(3))_(2)NH is more basic than (CH_(3))_(3)N in an aqueous solution. (iii) Ammonolysis of alkyl halides is not a good method to prepare pure primary amines. (b) Distinguish between the following : (i) CH_(3)CH_(2)NH_(2) and (CH_(3)CH_(2))_(2)NH (ii) Aniline and CH_(3)NH_(2) |
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Answer» Solution :(a) (i) In acidic medium, aniline is protonated to form to anilinium ion which is meta directing. That is why a good yield of m-nitroaniline is also obtained. (ii) There is greater solvation of substituted ammonium cation due to the presence of two hydrogens in SECONDARY amine compared to ONE hydrogen in tertiary amine. Due to COMBINED effect of inductive effect and solvation effect, `(CH_(3))_(2)NH` is more basic than `(CH_(3))_(3)N`. (iii) This is because ammonolysis yields a mixture of primary, secondary, tertiary and quaternary ammonium salt. (B) (i) `CH_(3)CH_(2)NH_(2)` and `(CH_(3)CH_(2))_(2)NH` The two compounds can be distinguished with Hinsberg.s reagent. The reaction of benzenesulphonyl chloride with `CH_(3)CH_(2)NH_(2)` gives N-Ethylbenzenesulphonamide which is soluble in alkali. The compound obtained with `(CH_(3)CH_(2))_(2)NH` is not soluble in alkali. (ii) Aniline and `CH_(3)NH_(2)` `CH_(3)NH_(2)` reacts with nitrous acid to liberate nitrogen gas. Aniline does not evolve `N_(2)` gas but forms a diazonium salt at 273-278 K. |
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