Asked in PMC Practice Test 13 (2021) 2021Moderate

Phenol gives electrophilic substitution reactions due to?

Correct answer: A. OH group

  • A. OH group
  • B. Phenoxide ion
  • C. Benzene ring
  • D. All of these options are correct

Explanation

OPTION A: Phenol is an aromatic alcohol, and the presence of a hydroxyl (OH) group in the molecule makes it an electrophilic substrate. The electrophilic character of the hydroxyl group arises due to the high electron density of the oxygen atom, which makes the hydroxyl proton acidic and a good leaving group. This makes the phenol molecule susceptible to electrophilic substitution reactions, where an electrophile can attack the molecule and replace the hydrogen in the hydroxyl group. OPTION B: Phenol does not give electrophilic substitution reactions due to Phenoxide ion because Phenoxide ion is a relatively stable species and is not very reactive. The negative charge on the oxygen in the Phenoxide ion is delocalized over the entire ring, reducing its reactivity and making it a poor electrophile. OPTION C: The benzene ring in the phenol does not contribute to its electrophilic character as it is a relatively stable and unactivated ring due to the delocalization of electrons in the aromatic system, so electrophilic substitution reactions typically occur at the OH group rather than the ring. OPTION D: This option is incorrect.

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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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