Aldehydes and Ketones, having at least one methyl group linked to the carbonyl carbon atom (methyl Ketones), are oxidised by sodium hypohalite to sodium salts of corresponding carboxylic acids having one carbon atom less than that of carbonyl compound is converted to haloform. This oxidation does not affect a carbon–carbon double bond, if present in a molecule.
Match List-I with List-II
| List-I | List-II |
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(I) Hydrazones |
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(II) oximes |
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(III) Ethane |
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(IV) Phenyl hydrazones |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A)-(II), (B)-(I), (C)-(IV), (D)-(III)
Ammonia derivatives (Z–NH2) add to the C=O group of aldehydes and ketones and then lose water (addition–elimination), giving a C=N–Z product. Clemmensen reduction removes the oxygen completely and turns >C=O into >\( \ce{CH2} \).
(A) \( \ce{CH3CHO} \) + \( \ce{H2NOH} \) — This matches (II) oximes. Hydroxylamine gives acetaldoxime:
\( \ce{CH3CHO + H2NOH} \xrightarrow{\ce{H+}} \ce{CH3CH=NOH + H2O} \)
(B) \( \ce{CH3CHO} \) + \( \ce{H2NNH2} \) — This matches (I) Hydrazones. Hydrazine gives acetaldehyde hydrazone:
\( \ce{CH3CHO + H2NNH2} \xrightarrow{\ce{H+}} \ce{CH3CH=NNH2 + H2O} \)
(C) \( \ce{CH3CHO} \) + \( \ce{H2NNHC6H5} \) — This matches (IV) phenyl hydrazones. Phenylhydrazine gives acetaldehyde phenylhydrazone:
\( \ce{CH3CHO + H2NNHC6H5} \xrightarrow{\ce{H+}} \ce{CH3CH=NNHC6H5 + H2O} \)
(D) \( \ce{CH3CHO} \) + Zn–Hg/HCl — This matches (III) Ethane. In Clemmensen reduction the carbonyl group is reduced to \( \ce{CH2} \):
\( \ce{CH3CHO + 4[H]} \xrightarrow[\ce{HCl}]{\ce{Zn-Hg}} \ce{CH3CH3 + H2O} \)
Shortcut: (D)-(III) appears only in Option (2).
Note: It seems that there is a mistake in the original NTA paper, which prints “… than that of carbonyl compound is converted to haloform” when it should read “… than that of carbonyl compound. The methyl group is converted to haloform”.