Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon than in aldehydes having only one such substituent. Electronically, aldehydes are more reactive than ketones because two alkyl groups reduce the electrophilicity of the carbonyl more efficiently than in the former.
Match List I with List II
| List I | List II |
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I. \(CrO_3 / H_2SO_4\) |
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II. \(H_3O^+ / \Delta\) |
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III. Ammoniacal silver nitrate |
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IV. \(KMnO_4 - H_2SO_4/\Delta\) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-IV, C-I, D-II
Each conversion is matched with the reagent that does that particular job: a mild oxidant for an aldehyde, a vigorous oxidant to cleave a C=C bond, an acidic chromium(VI) oxidant for a primary alcohol, and acid hydrolysis for an amide.
(A) \( \ce{CH3CH2CH2CHO -> CH3CH2CH2COOH} \) — This matches (III) Ammoniacal silver nitrate. An aldehyde is oxidised even by a mild oxidising agent such as Tollens’ reagent; acidification then gives the acid.
\( \displaystyle \ce{RCHO + 2[Ag(NH3)2]^+ + 3OH^- -> RCOO^- + 2Ag v + 2H2O + 4NH3} \)
(B) Cyclohexene → hexane-1,6-dioic acid (adipic acid) — This matches (IV) KMnO4–H2SO4/Δ. Vigorous oxidation cleaves the C=C bond, and each end becomes –COOH.
\( \displaystyle \ce{C6H10 + 4[O]} \xrightarrow{\ce{KMnO4/H2SO4},\ \Delta} \ce{HOOC(CH2)4COOH} \)
(C) \( \ce{CH3CH2CH2CH2OH -> CH3CH2CH2COOH} \) — This matches (I) CrO3/H2SO4. A primary alcohol is oxidised to the acid by chromium trioxide in acid (Jones reagent).
\( \displaystyle \ce{CH3CH2CH2CH2OH + 2[O]} \xrightarrow{\ce{CrO3/H2SO4}} \ce{CH3CH2CH2COOH + H2O} \)
(D) \( \ce{CH3CONH2 -> CH3COOH} \) — This matches (II) H3O+/Δ. An amide is hydrolysed by heating with dilute acid.
\( \displaystyle \ce{CH3CONH2 + H2O + H+} \xrightarrow{\Delta} \ce{CH3COOH + NH4+} \)
Shortcut: D, an amide, can only be converted to the acid by hydrolysis (II), and only Option (2) has D-II.
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 12-06 S3 10-06 S1 | – |