Asked in PMC National MDCAT 2020 2020Moderate

Phenol is more acidic than alcohols because of the following reason:

Correct answer: C. Delocalization of negative charge in the ring

  • A. Delocalization of negative charge in OH group
  • B. Delocation of positive charge on the carbon atom in ring
  • C. Delocalization of negative charge in the ring
  • D. Delocalization of positive charge in the OH group

Explanation

Phenol is more acidic than alcohols due to stabilisation of phenoxide ion through resonance of negative charge in the ring. Presence of electron withdrawing group (COOH,CF3) increases the acidity of phenol by stabilising phenoxide ion while presence of electron releasing group (OH, NH2) decreases the acidity of phenol by destabilising phenoxide 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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