See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: Stereoisomers of cyclic compounds arise from cis/trans relationships at stereocenters, and we must check for meso forms (which reduce the count of distinct stereoisomers). Step 1: Identify the stereocenters. In 1,3-dichlorocyclohexane, C1 and C3 each bear one Cl and are stereocenters (each has four different substituents when considering the ring connectivity). Step 2: Enumerate possible configurations. With two stereocenters, there are at most 2^2 = 4 stereoisomers. These correspond to: (1R,3R), (1S,3S), (1R,3S), and (1S,3R). Step 3: Check for meso forms. The molecule has a plane of symmetry consideration: (1R,3S) and (1S,3R) — because C1 and C3 are related by the mirror plane passing through C2 and C5 of the ring, the (1R,3S) form is identical to the (1S,3R) form. This is the cis isomer (both Cl on same face), and it is a meso compound — it is superimposable on its mirror image. So (1R,3S) and (1S,3R) count as only ONE compound (the cis-meso form). Step 4: Count distinct stereoisomers. - cis-1,3-dichlorocyclohexane: (1R,3S)/(1S,3R) → meso compound → 1 stereoisomer - trans-1,3-dichlorocyclohexane: (1R,3R) and (1S,3S) → enantiomers, not superimposable → 2 stereoisomers Total = 1 (cis-meso) + 2 (trans enantiomers) = 3 stereoisomers. Step 5: Why other options fail. - (a) 0: Incorrect; stereoisomers do exist. - (b) 1: Incorrect; this would ignore the trans enantiomeric pair. - (d) 4: Incorrect; this counts the meso pair as two separate compounds, which they are not. Therefore, the correct answer is C.