JEE Main 2026 — Jan 24, Shift 2 — Chemistry solution

JEE Main2026Jan 24, Shift 2Chemistry

The unsaturated ether on acidic hydrolysis produces carbonyl compounds as shown below:

$CH_{3} - CH = CH - O - CH = CH_{2} H_{3} O^{+} CH_{3} - CH_{2} - CH = O and O = CH - CH_{3}$

Based on this, predict the solution / reagent that will help to distinguish "P" and "Q" obtained in the following reaction.

Solution

Acidic hydrolysis of the unsaturated ether cleaves the $C - O - C$ linkage and tautomerizes the resulting enols to carbonyls:

$P = CH_{3} CH_{2} CHO$ (propanal, an aldehyde)

$Q = CH_{3} COCH_{3}$ (acetone, a ketone)

Fehling's solution oxidizes aliphatic aldehydes to give a red-brown $Cu_{2} O$ precipitate but does not react with ketones.

$∴$ P gives a positive Fehling test; Q gives a negative Fehling test. Fehling solution distinguishes them.

2,4-DNP and $NaHSO_{3}$ react with both aldehydes and ketones, so they cannot distinguish. Lucas reagent is for alcohols.

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