Answer: an alkene.
- A an aldehyde
- B an alkene
- C a ketone
- D a carboxylic acid
Correct answer: B. an alkene
Explanation: Lacking an alpha-hydrogen on the carbinol carbon, a tertiary alcohol cannot dehydrogenate; over hot copper it dehydrates to an alkene.
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.