See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the stereocenters: Both compounds are 4-methylcyclohexan-1-one derivatives (more precisely, they appear to be 2-methyl or 4-methyl cyclohexanones with two stereocenters). Each molecule has two stereocenters: C1 (bearing H, adjacent to carbonyl) and C4 (bearing methyl and H). Step 2 - Assign configurations: In Compound 1, the H at C1 is on a wedge (coming forward) and the H at C4 is on a dash (going back) with methyl also configured at C4. In Compound 2, the H at C1 is on a wedge and the methyl/H arrangement at C4 is inverted relative to Compound 1. This means the two compounds differ in configuration at only ONE of the two stereocenters (C4), while C1 retains the same configuration. Step 3 - Define epimers: Epimers are a specific type of diastereomer that differ in configuration at exactly one stereocenter when two or more stereocenters are present. Since the two compounds differ at only one stereocenter (C4) out of two total stereocenters, they are epimers. Step 4 - Why not enantiomers: Enantiomers are non-superimposable mirror images that differ at ALL stereocenters. Here only one stereocenter is inverted, so they are not enantiomers. Step 5 - Why not simply diastereomers (option a): While epimers are technically a subset of diastereomers, the more precise and specific term here is epimers (option c), which is the best answer. Step 6 - Why not regiomers: Regiomers (constitutional isomers differing in position of a substituent) do not apply here since both compounds have the same connectivity. Therefore, the correct answer is C.