JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

In the above reaction, the reagent "A" is:

(A) $NaBH_{4}, H_{3} O^{+}$
(B) $HCl, Zn - Hg$
(C) $LiAlH_{4}$
(D)Alkaline $KMnO_{4}, H^{+}$ ✓ Correct

Answer: (D)

Solution

The ring methyl group has become a carboxyl group while the methoxy group and the ring itself are untouched. Turning a side chain into

- COOH

calls for a strong oxidant that attacks the benzylic position, and acidification afterwards liberates the free acid from its salt. Sodium borohydride and lithium aluminium hydride are reducing agents and cannot raise the oxidation state of the side chain, while zinc amalgam with hydrochloric acid reduces a carbonyl group down to a methylene group. The reagent is alkaline potassium permanganate followed by acidification.

JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Single correct option

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JEE Main · 2021 · 16 Mar 2021 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Solution

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