Match List-I with List-II
| List-I Name reaction | List-II Reagent |
| (A) Wolff Kishner reaction | (I) Zn-Hg/HCl |
| (B) Clemmensen reduction reaction | (II) NH2NH2 , KOH / ethylene glycol, heat |
| (C) Jones Reagent | (III) H2, Pd-BaSO4 |
| (D) Rosenmund reagent | (IV) CrO3-H2SO4 |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
Many named reactions of aldehydes, ketones and their derivatives are recognised from the reagent used:
Reduction of C=O to CH2: Clemmensen reduction (zinc amalgam and conc. HCl, acidic conditions) and Wolff–Kishner reduction (hydrazine, then KOH in ethylene glycol on heating, basic conditions).
Partial reduction to an aldehyde: Rosenmund reduction of an acyl chloride with \( \ce{H2} \) over palladium on barium sulphate; Stephen reduction of a nitrile with \( \ce{SnCl2} \)/HCl.
Oxidation of alcohols: Jones reagent (\( \ce{CrO3-H2SO4} \)) oxidises primary alcohols to carboxylic acids and secondary alcohols to ketones; PCC stops primary alcohols at the aldehyde.
(A) Wolff Kishner reaction — This matches (II) NH2NH2 , KOH / ethylene glycol, heat. The carbonyl compound forms a hydrazone, which loses \( \ce{N2} \) on heating with KOH, converting C=O into CH2.
\( \displaystyle \ce{R2C=O + NH2NH2 -> R2C=N-NH2 + H2O} \)
\( \displaystyle \ce{R2C=N-NH2} \xrightarrow{\ce{KOH}\text{/ethylene glycol, heat}} \ce{R2CH2 + N2 ^} \)
(B) Clemmensen reduction reaction — This matches (I) Zn-Hg/HCl. Zinc amalgam and conc. HCl reduce the C=O group directly to CH2.
\( \displaystyle \ce{R2C=O + 4[H]} \xrightarrow{\ce{Zn-Hg}/\text{conc. }\ce{HCl}} \ce{R2CH2 + H2O} \)
(C) Jones Reagent — This matches (IV) CrO3-H2SO4. Chromium trioxide in aqueous sulphuric acid is a strong oxidant that converts a primary alcohol into a carboxylic acid.
\( \displaystyle \ce{RCH2OH + 2[O]} \xrightarrow{\ce{CrO3-H2SO4}} \ce{RCOOH + H2O} \)
(D) Rosenmund reagent — This matches (III) H2, Pd-BaSO4. An acyl chloride is hydrogenated over palladium poisoned with BaSO4, which stops the reduction at the aldehyde.
\( \displaystyle \ce{RCOCl + H2} \xrightarrow{\ce{Pd-BaSO4}} \ce{RCHO + HCl} \)
Shortcut: The pair (C)–(IV) appears in Options (3) and (4), and (B)–(I) then leaves only Option (4).