The formation of picric acid by phenols is called _.
Correct answer: D. Nitration
- A. Decomposition
- B. Halogenation
- C. Sulphonation
- D. Nitration
Explanation
When we are converting phenols into picric acid, which contains three nitronium ions, the first sulphonation takes place. The OH group of phenol is very active and therefore the nitration mixture gets overheated even using dilute nitric acid and oxidation takes place. Thus first we heat phenol with sulfuric acid to get phenol-2,4-disulphonic acid. This sulphonic acid is so electron-withdrawing that it starts the nitration more slowly and in a controlled manner. And then after that sulphonic acid groups keep substituting nitronium ions to make picric acid.
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About Alcohols and Phenols
Alcohols are classified as primary, secondary or tertiary and studied through their hydrogen bonding, acidity, oxidation and reactions with active metals, acids and halogenating agents. Phenols require separate treatment because the hydroxyl group is attached to an aromatic ring, making their acidity and electrophilic substitution different from ordinary alcohols.
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