Match List-I with List-II
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List-I |
List-II |
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(A) Coupling reaction |
(I) Primary amines |
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(B) Hofmann's degradation |
(II) Aromatic amines |
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(C) Isocyanide test |
(III) Phenols and aromatic amines |
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(D) Diazonium salts |
(IV) Amide to amine |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) - (III), (B) - (IV), (C) - (I), (D) - (II)
The four items are reactions and tests from the chemistry of amines and diazonium salts. Each one needs a particular kind of compound: an activated aromatic ring for coupling, an amide for the Hofmann reaction, a primary amine for the isocyanide test, and an aromatic primary amine for a stable diazonium salt.
(A) Coupling reaction — This matches (III) Phenols and aromatic amines. Benzenediazonium chloride couples with phenol (in alkaline medium) or with aniline (in acidic medium) at the para position to give coloured azo compounds.
\( \displaystyle \ce{C6H5N2+Cl^- + C6H5OH} \xrightarrow{\ce{OH-}} \ce{C6H5N=NC6H4OH}\,(p\text{-hydroxyazobenzene, orange}) + \ce{HCl} \)
(B) Hofmann's degradation — This matches (IV) Amide to amine. An amide heated with bromine and sodium hydroxide gives a primary amine with one carbon atom less.
\( \displaystyle \ce{RCONH2 + Br2 + 4NaOH -> RNH2 + Na2CO3 + 2NaBr + 2H2O} \)
(C) Isocyanide test — This matches (I) Primary amines. Primary amines (aliphatic and aromatic) heated with chloroform and alcoholic KOH give foul-smelling isocyanides; secondary and tertiary amines do not.
\( \displaystyle \ce{RNH2 + CHCl3 + 3KOH} \xrightarrow{\Delta} \ce{RNC + 3KCl + 3H2O} \)
(D) Diazonium salts — This matches (II) Aromatic amines. Primary aromatic amines react with nitrous acid at 273–278 K to give arenediazonium salts, which are stable at low temperature (aliphatic ones decompose at once).
\( \displaystyle \ce{C6H5NH2 + NaNO2 + 2HCl} \xrightarrow{273-278\ \mathrm{K}} \ce{C6H5N2+Cl^- + NaCl + 2H2O} \)