See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Tautomerism Analysis **Tautomerism** requires the presence of an active hydrogen atom (typically on a carbon adjacent to a carbonyl or similar group) that can migrate to form a structural isomer. ## Evaluating Each Option: **(A) PhCOCOPh** ✗ Cannot exhibit tautomerism - Both carbonyls are directly bonded to each other (α-dicarbonyl) - No hydrogen atom exists on the carbon between the two carbonyls - No migration possible → **No tautomerism** **(B) PhCOCH(CH₃)COPh** ✓ Can exhibit tautomerism - Has active hydrogen on the central carbon (CH group between two carbonyls) - Can undergo keto-enol tautomerism: $$\text{PhCOCH(CH}_3\text{)COPh} \rightleftharpoons \text{PhC(OH)=C(CH}_3\text{)COPh}$$ **(C) PhCOCMe₃** ✗ Cannot exhibit tautomerism - The carbon attached to the carbonyl is quaternary (CMe₃) - No hydrogen atoms on this carbon - Cannot migrate → **No tautomerism** **(D) Cl₃C-CHO** ✗ Cannot exhibit tautomerism - The aldehyde carbon has no neighboring carbon with hydrogens - The adjacent carbon (CCl₃) is quaternary with no hydrogens - No active hydrogen available → **No tautomerism** **(E) HO-CH₂-C(=O)-Ph** ✓ Can exhibit tautomerism - Has active hydrogen on α-carbon - Can form enol form through keto-enol tautomerism **Answer: A, C, D cannot exhibit tautomerism** due to absence of active hydrogen atoms on carbons adjacent to the carbonyl group.