See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of the Given Structure **Identifying the functional groups:** - The structure contains a C=C double bond with different substituents (geometric isomerism potential) - More critically, it has a **carboxylic acid group (–COOH)** adjacent to a carbon bearing a **methyl group (–CH₃)** **Why this is Tautomerism, not just geometric/optical isomerism:** The carboxylic acid can undergo **keto-enol tautomerism**: $$\text{R-CH}_2\text{-COOH} \rightleftharpoons \text{R-CH=C(OH)}_2 \rightleftharpoons \text{R-C(OH)=CH}_2$$ More specifically, the acidic hydrogen of –COOH can migrate to the adjacent C=C double bond, converting it to a C–C single bond while the C=C becomes a ketone or enol form. This represents **rapid, dynamic equilibrium between different structural isomers** (not just stereoisomers). **Why not (A), (B), or (C):** - (A) Geometric isomerism alone: Doesn't account for the structural changes from tautomerism - (B) Optical isomerism: No chiral center is created/destroyed - (C) Both geometric & optical: Still doesn't explain the hydrogen migration **Answer: (D) Tautomerism** — The compound exhibits keto-enol tautomerism due to the α-hydrogen on the carboxylic acid group being in equilibrium with enolic forms.