See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: OsO4 performs syn-dihydroxylation, adding two OH groups to the same face of a double bond. Step 1: Identify the substrate. Cyclopentene is a symmetric cyclic alkene. The double bond carbons (C1 and C2) are equivalent by symmetry. Step 2: Determine the product. OsO4 adds syn (cis) across the double bond of cyclopentene, giving cis-1,2-cyclopentanediol. Both OH groups are added to the same face. Step 3: Analyze stereochemistry of cis-1,2-cyclopentanediol. C1 and C2 are both stereocenters. Syn addition from the top face gives (1R,2S) and syn addition from the bottom face gives (1S,2R). However, because the molecule has an internal plane of symmetry (the mirror plane passing through the midpoint of C1-C2 and through C3, C4, C5 axis), (1R,2S) is actually the same compound as (1S,2R) — this is a meso compound. Step 4: A meso compound is achiral — it has stereocenters but is superimposable on its mirror image due to an internal plane of symmetry. Therefore it is not optically active and does not form a racemic mixture. Step 5: Evaluate options: - (a) achiral: CORRECT — meso compounds are achiral. - (b) racemic: INCORRECT — a racemic mixture consists of equal amounts of two enantiomers; here only one compound (the meso form) is produced. - (c) meso: CORRECT — cis-1,2-cyclopentanediol is a meso compound. - (d) optically active: INCORRECT — meso compounds do not rotate plane-polarized light. Therefore, the correct answer is A,C.