Q. 19

(a) Give one chem

Answer :

a(i)


Methylamine is an aliphatic primary amine and dimethylamine is a secondary amine, hence they can be distinguish on the basis of their degree and corresponding reaction.


Carbylamine test might be the most suitable test to distinguish between them in which the only aliphatic primary amine reacts on heating with chloroform in alcoholic KOH medium which produces foul-smelling isocyanides or carbylamines.


Hence the foul smell is the physical indicator of the reaction and methylamine responds to it while dimethylamine does not which clearly the difference between them.


CH3-NH2 + CHCl3 + 3KOH CH3-NC + 3KCl + 3H2


Methylamine(1°) Methyl isocyanide(foul smell)


(CH3)2NH + CHCl3 + 3KOH No reaction.


a(ii)


Aniline and benzylamine this two aromatic compounds can be distinguished by their characteristic reactions towards nitrous acid (diazotization) followed by test of coupling reaction.


Aniline on reaction with HNO2 gives a very stable diazonium salt which on coupling/azo-dye test obviously gives azo dye (the colour and texture is the identification)



whereas same reaction of HNO2 andbenzylamine gives rise to a very unstable diazonium salt which ultimately produces benzyl alcohol (with water) with the evolution of N2 gas which is not the case for aniline.


therefore, does not give positive azo-dye test which is the clear distinguishing test for both.



(b) There are 4 types of different structures as follows;


CH3-CH2-CH2_NH2


Propan-1-amine(Primary)


N-methylethanamine(Secondary)



N, N-Dimethyl methanamine(Tertiary)



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