Match List-I with List-II
|
List-I |
List-II |
|
(A) Acetone to secondary alcohol |
(I) \( CrO_3 \) |
|
(B) Ethanol to Diethyl ether |
(II) Zn |
|
(C) Ethanol to ethanal |
(III) \( NaBH_4 \) |
|
(D) Phenol to Benzene |
(IV) \( H_2SO_4 \) at 413 K |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
Each conversion needs a reagent of a different kind: a reducing agent to turn a ketone into an alcohol, an acid at a controlled temperature to dehydrate an alcohol to an ether, a mild oxidising agent to stop the oxidation of a primary alcohol at the aldehyde, and a metal that removes oxygen from phenol.
(A) Acetone to secondary alcohol — This matches (III) \(NaBH_4\). Sodium borohydride transfers a hydride ion to the carbonyl carbon; ketones give secondary alcohols:
\( \displaystyle \ce{CH3COCH3} \xrightarrow{\ce{NaBH4}} \ce{CH3CH(OH)CH3} \quad (\text{propan-2-ol}) \)
(B) Ethanol to Diethyl ether — This matches (IV) \(H_2SO_4\) at 413 K. At 413 K two molecules of ethanol lose one molecule of water between them; at 443 K the same acid gives ethene instead:
\( \displaystyle \ce{2C2H5OH} \xrightarrow[\text{413 K}]{\text{conc. }\ce{H2SO4}} \ce{C2H5-O-C2H5 + H2O} \)
(C) Ethanol to ethanal — This matches (I) \(CrO_3\). \( \ce{CrO3} \) in anhydrous medium oxidises a primary alcohol only as far as the aldehyde; a strong oxidising agent such as acidified \( \ce{KMnO4} \) would go on to the acid:
\( \displaystyle \ce{CH3CH2OH} \xrightarrow{\ce{CrO3}} \ce{CH3CHO} \)
(D) Phenol to Benzene — This matches (II) Zn. When phenol is heated with zinc dust, zinc takes up the oxygen:
\( \displaystyle \ce{C6H5OH + Zn} \xrightarrow{\Delta} \ce{C6H6 + ZnO} \)
Shortcut: (A)-(III) appears only in Option (4).