Answer: has intramolecular hydrogen bonding.
- A is the only aromatic one
- B has a much higher molar mass
- C is a far stronger acid
- D has intramolecular hydrogen bonding
Correct answer: D. has intramolecular hydrogen bonding
Explanation: Intramolecular H-bonding (chelation) in o-nitrophenol keeps molecules separate, while p-nitrophenol forms intermolecular H-bonds and is non-volatile.
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.