Answer: 108.9°.
- A 108.9°
- B 104.5°
- C 90°
- D 120°
Correct answer: A. 108.9°
Explanation: The oxygen is roughly sp<sup>3</sup>; slight lone-pair repulsion gives a C-O-H angle of about 108.9°.
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.