JEE Advanced 2026 — Paper 1 — CHEM-III solution

JEE Advanced2026Paper 1CHEM-III

The sum of total number of carbonyl groups (>C=O) present in the major products $X$ and $Y$ in the following reactions is _____.

Your answer

Solution

Reaction (i). A β-keto acid loses CO $_{2}$ on heating (decarboxylation). The given diacid has two β-keto carboxylic acid groups (each CO $_{2}$ H is β to the central ketone), so both decarboxylate to give pentan-3-one (CH $_{3}$ CH $_{2}$ –CO–CH $_{2}$ CH $_{3}$ ). $X$ contains 1 carbonyl group.

Reaction (ii). trans-3,4-dicarboxy-cyclopentanone has two adjacent –CO $_{2}$ H groups on neighbouring ring carbons. On heating, these undergo intramolecular dehydration to form a cyclic anhydride, fused to the unchanged cyclopentanone ring. The product $Y$ is a bicyclic system containing one ring ketone (C=O) and two anhydride carbonyls (–CO–O–CO–), giving 3 carbonyl groups.

Sum = $1 + 3 = 4.00$ .

← Back to full paper

Practice more CHEM-III

Concept-wise practice with instant solutions on Fundamenthol.

Start practicing →