Answer: Zn(Hg) with HCl.
- A Zn(Hg) with HCl
- B NH2NH<sub>2</sub> with KOH
- C LiAlH<sub>4</sub>
- D NaBH<sub>4</sub>
Correct answer: A. Zn(Hg) with HCl
Explanation: Clemmensen reduction uses zinc amalgam and hydrochloric acid to reduce carbonyls to CH<sub>2</sub>.
The phenoxide ion's negative charge spreads into the aromatic ring through resonance, lowering its energy and making phenol give up its proton more easily; an alkoxide ion (from a plain alcohol) has nowhere to delocalise the charge, making alcohols far less acidic.
Concept context
Oxygen-containing organic compounds. Understand the acidic nature of phenols, reactions of alcohols (dehydration, oxidation, esterification), and properties of ethers. Includes industrial applications and named reactions.