See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Dihydroxylation of alkenes can proceed via syn or anti addition. The stereochemical outcome depends on the reagent used. Step 1 - Understand the target: Trans-cyclohexane-1,2-diol has two OH groups on opposite faces of the ring (anti addition product). Step 2 - Analyze each reagent: (a) KMnO4 (cold, dilute) gives syn dihydroxylation → cis-diol. Hot, concentrated KMnO4 causes oxidative cleavage, not diol formation. So KMnO4 does not give the trans-diol. (b) OsO4 gives syn dihydroxylation (both OH groups added to the same face) → cis-diol. This is the classic reagent for cis-diols. (c) Peroxy formic acid (performic acid) first forms an epoxide (via epoxidation of cyclohexene), then H3O+ (acid-catalyzed hydrolysis) opens the epoxide via backside (anti) attack of water → anti addition → trans-cyclohexane-1,2-diol. This is the correct pathway. (d) SeO2 is used for allylic oxidation (introduction of a carbonyl or allylic alcohol), not for vicinal diol formation. Step 3 - Conclusion: Peroxy formic acid epoxidizes cyclohexene to give cyclohexene oxide, and subsequent acid-catalyzed ring opening with water proceeds with inversion (anti addition), yielding the trans-1,2-diol. Therefore, the correct answer is C.