Answer: but-2-ene.
- A but-1-ene
- B butane
- C but-2-ene
- D butan-1-ol
Correct answer: C. but-2-ene
Explanation: Dehydration goes through a carbocation and follows Saytzeff's rule, favouring the more substituted but-2-ene.
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.