JEE Main 2026 Apr 6 Shift 2, Chemistry Q14: Properties and Important Reactions of Aldehydes & Ketones

JEE Main2026Apr 6, Shift 2Chemistry

' $x$ ' 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 ethanenitrile with methyl magnesium bromide in dry ether followed by hydrolysis. IUPAC name of the product obtained from ' $x$ ' and ' $y$ ' in the presence of barium hydroxide followed by heating is:

A
2-Methylpent-4-en-3-one
B
4-Methylpent-3-en-2-one
C
4-Methylpent-1-ene
D
2-Methylpent-3-one

Solution

Form $x$ . Kucherov hydration of propyne (CH $_{3}$ –C≡CH) with HgSO $_{4}$ /dil. H $_{2}$ SO $_{4}$ follows Markovnikov: the OH lands on the more substituted carbon, giving an enol that tautomerises to acetone (propan-2-one), CH $_{3}$ –CO–CH $_{3}$ .

Form $y$ . CH $_{3}$ –C≡N + CH $_{3}$ MgBr followed by aqueous workup gives a ketone: acetone as well (CH $_{3}$ –CO–CH $_{3}$ ). (Grignard + nitrile $\to$ imine $\to$ ketone on hydrolysis.)

Combine $x$ and $y$ . Two molecules of acetone undergo aldol condensation under Ba(OH) $_{2}$ /heat. The $α$ -carbanion of one acetone adds to the carbonyl of another, giving the $β$ -hydroxy ketone (diacetone alcohol), which dehydrates to mesityl oxide: (CH $_{3}$ ) $_{2}$ C=CH–CO–CH $_{3}$ .

IUPAC name: 4-methylpent-3-en-2-one.

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JEE Main 2026 Apr 6 Shift 2, Chemistry Q14: Properties and Important Reactions of Aldehydes & Ketones

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