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JEE Main 202624 JanuaryEvening Shift
Exam
JEE Main
Year
2026
Date
24 January
Shift
Evening Shift
Subject
Chemistry
Chapter
Alcohols Phenols and Ethers

JEE Main 2026 · 24 January · Evening Shift · Chemistry · Alcohols Phenols and Ethers

The unsaturated ether on acidic hydrolysis produces carbonyl...

The unsaturated ether on acidic hydrolysis produces carbonyl compounds as shown below:- CH3−CH=CH−O−CH=CH2↓H3O(+)CH3−CH2−CH=O and O=CH−CH3\begin{aligned} \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}- & \mathrm{O}-\mathrm{CH}=\mathrm{CH}_{2} \\ & \downarrow \mathrm{H}_{3} \mathrm{O}^{(+)} \\ \mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}= & \mathrm{O} \text{ and } \mathrm{O}=\mathrm{CH}-\mathrm{CH}_{3} \end{aligned} Based on this, predict the solution/reagent that will help to distinguish " P " and " Q " obtained in the following reaction:-

Options

  1. AFehling solution
  2. BLucas reagent
  3. C2, 4 - DNP reagent
  4. DSaturated NaHSO3\mathrm{NaHSO}_{3} solution

Correct answer

A. Fehling solution

Step-by-step solution

Acidic hydrolysis of vinyl ethers involves the addition of water across the double bond followed by the elimination of alcohol/phenol to form carbonyl compounds. In the given reaction:
CH3−CH=CH−O−C(CH3)=CH2→H3O+P+QCH_3-CH=CH-O-C(CH_3)=CH_2 \xrightarrow{H_3O^+} P + Q
The hydrolysis occurs at both vinyl ether linkages.
The left part CH3−CH=CH−O−CH_3-CH=CH-O- hydrolyzes to form propanal: CH3−CH2−CHOCH_3-CH_2-CHO (P).
The right part −O−C(CH3)=CH2-O-C(CH_3)=CH_2 hydrolyzes to form acetone: CH3−CO−CH3CH_3-CO-CH_3 (Q).
P is an aldehyde (propanal) and Q is a ketone (acetone).
Fehling solution is used to distinguish between aldehydes and ketones. Aldehydes (except benzaldehyde) reduce Fehling solution to give a red precipitate of Cu2OCu_2O, while ketones do not react.
Lucas reagent is used for alcohols. 2,4-DNP reacts with both aldehydes and ketones. Saturated NaHSO3NaHSO_3 reacts with most aldehydes and methyl ketones, so it is not the best choice for distinguishing these specific compounds compared to Fehling solution.
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