Asked in UHS MDCAT 2017 2017Moderate

The phenoxide ion is more stable than ethoxide ion as:

Correct answer: A. The lone pair on the oxygen atom overlaps with the delocalized π- bonding system in benzene.

  • A. The lone pair on the oxygen atom overlaps with the delocalized π- bonding system in benzene.
  • B. Oxygen atom is directly bonded with the benzene ring in the phenoxide ion.
  • C. The negative charge is localized on the oxygen atom of phenoxide ion.
  • D. The negative charge is delocalized on oxygen atom of ethoxide ion.

Explanation

In phenoxide ion, the lone pair on the oxygen atom forms a delocalised pi system with the benzene ring by involving the electrons of the ring. Moreover, oxygen is highly electronegative and it is stabilized by resonance. That's why phenoxide ion is more stable than ethoxide ion.

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About Phenols

Phenols contain a hydroxyl group directly bonded to an aromatic ring, making them more acidic than alcohols because the phenoxide ion is resonance-stabilised. Reactions include ionisation with bases, electrophilic substitution, bromination, nitration and oxidation, with attention to the difference between phenols and aliphatic alcohols.

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