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Chemistry Question 64 – JEE-MAIN 2026

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'X' is the product which is obtained by the hydrolysis of prop-1-yne in the presence of mercuric sulphate under dilute acidic medium at 333 K. 'Y' is the product which is obtained by the reaction of ethane nitrile with methyl magnesium bromide in dry ether followed by hydrolysis. IUPAC name of product obtained from 'X' and 'Y' in the presence of barium hydroxide followed by heating is :

Identify the type of reactions involved in forming 'X' and 'Y', and then the reaction between 'X' and 'Y'.

Step 1: Determine the structures of 'X' and 'Y'✦ Active

Product 'X' is obtained by the hydrolysis of prop-1-yne (CH3−C≡CH) in the presence of HgSO4/H2SO4. This is Markovnikov's addition of water to an alkyne, forming an enol (CH3−C(OH)=CH2) which tautomerizes to propan-2-one (CH3−CO−CH3). Thus, X=CH3−CO−CH3.

Product 'Y' is obtained by the reaction of ethane nitrile (CH3−C≡N) with methyl magnesium bromide (CH3MgBr) followed by hydrolysis. The Grignard reagent adds to the nitrile, forming an imine intermediate (CH3−C(=NMgBr)−CH3), which upon hydrolysis yields propan-2-one (CH3−CO−CH3). Thus, Y=CH3−CO−CH3.

Step 2: Identify the reaction between 'X' and 'Y' and the intermediate product○ Expand

The reaction of propan-2-one (X) with propan-2-one (Y) in the presence of barium hydroxide (Ba(OH)2) followed by heating is an aldol condensation. Propan-2-one has α-hydrogens, allowing it to form an enolate and act as a nucleophile. The aldol product formed before heating is 4-hydroxy-4-methylpentan-2-one.

2CH3−CO−CH3→Ba(OH)2(CH3)2C(OH)−CH2−CO−CH3
💡 Teacher's Secret Hint

Remember that aldol condensation involves both addition and subsequent dehydration upon heating.

Step 3: Determine the final product after heating and its IUPAC name○ Expand

Upon heating, the aldol product (4-hydroxy-4-methylpentan-2-one) undergoes dehydration to form an α,β-unsaturated ketone.

(CH3)2C(OH)−CH2−CO−CH3→Δ(CH3)2C=CH−CO−CH3+H2O

The IUPAC name of this final product is 4-methylpent-3-en-2-one. This matches option 2.

💡 Teacher's Secret Hint

Ensure correct numbering for the IUPAC name, prioritizing the carbonyl group.

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