See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

## Solution **Step 1: Determine the molecular formula of propionic acid** Propionic acid is $CH_3CH_2COOH$ with molecular formula $\boxed{C_3H_6O_2}$ **Step 2: Check each option for isomers with formula $C_3H_6O_2$** **(A)** $HCOOC_2H_5$ & $CH_3COOCH_3$ - $HCOOC_2H_5$ = $HC_2H_5O_2$ = $C_3H_6O_2$ ✓ (ethyl formate) - $CH_3COOCH_3$ = $C_2H_3O_2 \cdot CH_3$ = $C_3H_6O_2$ ✓ (methyl acetate) - Both are esters and functional isomers of propionic acid ✓ **(B)** $HCOOC_2H_5$ & $C_3H_7COOH$ - $HCOOC_2H_5$ = $C_3H_6O_2$ ✓ - $C_3H_7COOH$ = $C_4H_8O_2$ ✗ (different molecular formula—too many carbons) **(C)** $CH_3COOC_2H_5$ & $C_3H_7OH$ - $CH_3COOC_2H_5$ = $C_4H_8O_2$ ✗ (butanoate, not propionic acid) - Wrong formula **(D)** $C_3H_7OH$ & $CH_3COOCH_3$ - $C_3H_7OH$ = $C_3H_8O$ ✗ (propanol, not $C_3H_6O_2$) - Wrong formula **Answer: (A)** Both ethyl formate and methyl acetate are $C_3H_6O_2$ isomers—functional isomers of propionic acid (ester vs. carboxylic acid).