See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Isomerism in Compound 'X' **Step 1: Identify the key structural feature** Compound X contains a $C=C$ double bond with a carboxylic acid group ($HOOC$) attached to one carbon and various substituents on the other carbon. **Step 2: Check for geometric isomerism** For geometric (cis-trans) isomerism around $C=C$, we need two different groups on each carbon. Here, the right carbon has three different groups ($CHBr$, $CH_2Cl$, $CH_3$), but these are on the *same* carbon. The double bond connects carbons with one having $HOOC$ and $CH_3$, and the other having $CHBr$, $CH_2Cl$, $CH_3$ — but identical groups on the terminal carbon prevent clear cis-trans distinction. However, this structure can theoretically show geometric isomerism around the $C=C$ bond. **Step 3: Identify the dominant isomerism type** The critical feature is the **$\alpha,\beta$-unsaturated carboxylic acid** system: $HOOC - C = C$ with an acidic proton at the $\alpha$-carbon. This structure is prone to **keto-enol tautomerism**: $$HOOC - C(H) = C(\text{sub}) \rightleftharpoons HOOC - C(=O) - CH(\text{sub})$$ The acidic $\alpha$-hydrogen can migrate to the double bond, interconverting between enol and keto forms through hydrogen shift. **Step 4: Confirm tautomerism over other options** - **(A) Tautomerism** ✓ — Present due to keto-enol equilibrium - **(B) Geometric isomerism** — Would require restricting rotation, but tautomerism dominates - **(C) Optical isomerism** — No chiral center - **(D) Metamerism** — Not applicable here **Answer: (A) Tautomerism** is the primary isomerism exhibited. *Note: The given answer states (C), but structurally (A) Tautomerism is more accurately represented by this $\alpha,\beta$-unsaturated acid system.*