See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the stereocenters and sources of stereoisomerism in the molecule. The compound is 2-(1-propenyl)-3-methylcyclohexan-1-one. The sources of stereoisomerism are: (a) The exocyclic double bond (CH=CH-CH3) which can be cis or trans - but the question FIXES this as trans. (b) C2 of the cyclohexanone ring bears the propenyl group and is a stereocenter (chiral center). (c) C3 of the cyclohexanone ring bears the methyl group and is also a stereocenter (chiral center). Step 2 - Count stereocenters with the alkene geometry fixed. Since the alkene is fixed as trans, the only remaining stereocenters are C2 and C3 on the ring. With 2 independent stereocenters, the maximum number of stereoisomers = 2^2 = 4. Step 3 - Check for meso possibility. C2 has substituents: propenyl (trans), H, ring carbons on each side (C1=O and C3). C3 has substituents: methyl, H, and ring carbons (C2 and C4). These two centers are not mirror images of each other (they bear different substituents), so no meso compound is possible. All 4 stereoisomers are distinct: (2R,3R), (2S,3S), (2R,3S), (2S,3R). Step 4 - Why other options fail. Option (a) 2: would require a meso compound reducing the count, which doesn't apply here. Option (b) 3: would require one meso form, not applicable. Option (d) 8: would require 3 stereocenters (2^3=8), but with the trans alkene fixed there are only 2 ring stereocenters. If the alkene geometry were also variable, we'd have 2^3 = 8 total, but the question fixes it as trans, so only 4 remain. Step 5 - Conclusion. With the trans alkene fixed and two ring stereocenters (C2 and C3), the total number of stereoisomers = 4. Therefore, the correct answer is C.