See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Identifying Non-Isomeric Pairs **Isomers** have the same molecular formula but different structural arrangements. Let me check the molecular formula for each pair: ## (1) Ethyl ethanoate and methyl propanoate - Ethyl ethanoate: $CH_3COOC_2H_5$ → $C_4H_8O_2$ - Methyl propanoate: $C_2H_5COOCH_3$ → $C_4H_8O_2$ - **Same formula** ✓ (isomers) ## (2) Butanone and butanal - Butanone: $CH_3COCH_2CH_3$ → $C_4H_8O$ - Butanal: $CH_3CH_2CH_2CHO$ → $C_4H_8O$ - **Same formula** ✓ (functional isomers) ## (3) Ethoxy propane and ethyl propyl ether - Ethoxy propane: $C_2H_5OC_3H_7$ → $C_5H_{12}O$ - Ethyl propyl ether: $C_2H_5OC_3H_7$ → $C_5H_{12}O$ - **Same formula** ✓ (structural isomers) ## (4) Methoxy methane and ethanol - Methoxy methane (dimethyl ether): $CH_3OCH_3$ → $C_2H_6O$ - Ethanol: $C_2H_5OH$ → $C_2H_6O$ - **Same formula** ✓ (isomers) **Answer: (4)** — Despite both having the same molecular formula $C_2H_6O$, methoxy methane is an **ether** while ethanol is an **alcohol**. They are actually **functional isomers**, not "non-isomeric." If the question asks which pair are NOT isomeric, there may be an error in the question. However, if interpreted as "which pair differs most in properties despite same formula," **(4)** shows the greatest functional difference.