question_answer

                                        Describe a chemical test to distinguish between N-methylpropan-2-amine and N-ethyl-N-methylethanamine.                                   

Answer:

                                                These amines can distinguished by Liebermann nitrosoamine reaction and Hinsberg's reagent test. (i) Liebermann nitrosoamine reaction. N-methylpropan-2-amine being a \[2{}^\circ \] amine reacts with \[HN{{O}_{2}}(NaN{{O}_{2}}+HCl)\]at 273-278 K to give yellow coloured oily N-methyl-N-nitrosopropan-2 -amine. This, on warming with a crystal of phenol and conc. \[{{H}_{2}}S{{O}_{4}}\]gives a green solution which when made alkaline with aqueous \[NaOH\] turns deep blue and then red on dilution. This is called Liebermann nitrosoamine reaction.                                                                                                                                                                                                                     On the other hand, N-ethyl-N-methylethanamine being a amine does not give this test.               (ii) Hinsberg's reagent test. N-Methylpropan-2-amine being a \[2{}^\circ \] amine, on treatment with Hinsberg's reagent, i.e., benzenesulphonyl chloride \[({{C}_{6}}{{H}_{5}}S{{O}_{2}}Cl)\] forms N-isopropyl-N-methylbenzenesulphonainide which does not dissolve in aqueous NaOH due to absence of a H atom on the N-atom, On the other hand, N-ethyl-N-methylethanamine being a \[3{}^\circ \] amine does not react with Hinseberg's reagent and hence can be easily distilled off from the reaction mixture.