A Levels Chemistry (9701)•9701/13/M/J/23
Explanation
Dehydration to alkene followed by syn dihydroxylation
Steps:
- Cyclohexanol, a secondary alcohol, undergoes acid-catalyzed dehydration to form cyclohexene.
- Strong heating with Al2O3 acts as a dehydrating agent to yield the alkene.
- Cold, dilute KMnO4 in neutral or slightly basic conditions performs syn addition of two OH groups across the double bond.
- This sequence produces cyclohexane-1,2-diol without rearrangement.
Why A is correct:
- Al2O3 dehydration follows Zaitsev's rule to give cyclohexene; cold dilute KMnO4 enables Baeyer-Villiger-like syn dihydroxylation per organic reaction mechanisms.
Why the others are wrong:
- B: Reflux with NaOH deprotonates the alcohol but fails to dehydrate it to an alkene.
- C: Ethanolic NaOH forms alkoxide without dehydration; steam/H2SO4 hydrates any alkene to alcohol, not diol.
- D: Identical to C, yielding no diol via incorrect hydration.
Final answer: A
Topic: Hydroxy compounds
Practice more A Levels Chemistry (9701) questions on mMCQ.me