question_answer

Match the organic compounds in column-I with the Lassaigne's test results in column-II appropriately:

	Column-I		Column-II
[A]	Aniline	(i)	Red colour with \[FeC{{l}_{3}}\]
[B]	Benzene sulfonic acid	(ii)	Violet colour with sodium
[C]	Thiourea	(iii)	Blue colour with hot and acidic solution of \[FeS{{O}_{4}}\]

A) A\[\to \](ii); B\[\to \](iii); C\[\to \](i)

B) A\[\to \](iii); B\[\to \](i); C\[\to \](ii)

C) A\[\to \](iii); B\[\to \](ii); C\[\to \](i)

D) A\[\to \](ii); B\[\to \](i); C\[\to \](iii)

Correct Answer: B

Solution :

[b] In Lassaigne's test, fusion with sodium take place and following species formed respectively. [a] Aniline \[\xrightarrow{{}}C{{N}^{-}}\] [b] Benzene sulfonic acid \[\xrightarrow{{}}\] [c] Thiourea \[\xrightarrow{{}}{{S}^{2-}}\] Reaction of \[C{{N}^{-}}\] with hot and acidic solution of \[FeS{{O}_{4}}\] lead to formation of \[F{{e}_{4}}{{[FeCN)}_{6}}{{]}_{3}}\] which is blue in colour. It contains iron in both II and III oxidation state. Reaction of \[{{S}^{2-}}\] with sodium nitroprusside \[N{{a}_{2}}S+N{{a}_{2}}[Fe{{(CN)}_{5}}NO]\xrightarrow{{}}\underset{(violet\,\,in\,\,colour)}{\mathop{N{{a}_{4}}[Fe{{(CN)}_{5}}NOS]}}\,\] Phenoxide ion on reacting with \[FeC{{l}_{3}}\] give red colour with \[FeC{{l}_{3}}.\]