NEET 2019 · ChemistryPrevious Year Question
The compound that is most difficult to protonate is:
Answer: (D) (phenol). \textbf{Answer:} (d) phenol \textbf{Solution:} Ease of protonation depends on the availability (basicity) of the oxygen lone pair.
- A. (water)
- B. (methanol)
- C. (dimethyl ether)
- D. (phenol)✓
Correct Answer
(D) (phenol)
Solution & Explanation
\textbf{Answer:} (d) phenol \textbf{Solution:} Ease of protonation depends on the availability (basicity) of the oxygen lone pair. In phenol, one oxygen lone pair is delocalised into the benzene ring by resonance (the ring withdraws electron density via ), so the oxygen is the least basic and least available for protonation. In water, methanol and dimethyl ether the lone pairs are localised, and the alkyl groups are even electron-donating (), increasing basicity. Therefore phenol is the most difficult to protonate.
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