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Which of the following reactions can produce phenol as a product? (A) Salicylic acid (o-hydroxybenzoic acid) treated with NaOH/CaO and heat. (B) Benzenesulfonic acid treated with fused KOH. (C) Phenylcyclohexane treated with O2 under light/heat to give intermediate A, then A treated with H+ and heat. (D) Chlorobenzene treated with aqueous KOH.
- (A) Decarboxylation of salicylic acid with NaOH/CaO and heat
- (B) Alkali fusion of benzenesulfonic acid with fused KOH
- (C) Oxidative cleavage of phenylcyclohexane via hydroperoxide and acid
- (D) Hydrolysis of chlorobenzene with aqueous KOH
Correct answer: (A) Decarboxylation of salicylic acid with NaOH/CaO and heat
Solution
A: Salicylic acid + NaOH/CaO, heat = decarboxylation (soda lime reaction) -> phenol + CO2. YES. B: Benzenesulfonic acid + fused KOH = alkali fusion -> sodium phenoxide -> phenol on acidification. YES. C: Phenylcyclohexane + O2/hv,heat -> hydroperoxide (Hock rearrangement) -> phenol + cyclohexanone under H+. YES. D: Chlorobenzene + aq.KOH at room temperature or mild heat -> no significant reaction. Requires ~300 C and high pressure (Dow process) or special catalysts. Under normal conditions: NO phenol. Answer: A, B, C.
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