Phenoxide ion, produced by treating phenol with sodium hydroxide, undergoes electrophilic substitution with carbon dioxide in Kolbe’s reaction, forming ortho hydroxybenzoic acid as the main product. The phenoxide ion is more reactive than phenol due to its enhanced nucleophilicity.
Describe the electrophilic aromatic substitution in Kolbe’s reaction with phenoxide ion generated from phenol. What is the main product, and why is the phenoxide ion more reactive than phenol in this reaction?
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In Kolbe’s reaction, phenol undergoes electrophilic aromatic substitution with sodium phenoxide (generated from phenol by reacting it with sodium hydroxide). The main product is salicylic acid. The phenoxide ion is more reactive than phenol due to resonance stabilization. The negative charge on oxygen can delocalize onto the aromatic ring, creating a more stable intermediate. This enhanced stability makes the phenoxide ion a better nucleophile in electrophilic aromatic substitution reactions. The nucleophilic attack on carbon dioxide (CO₂) results in the formation of salicylate, and subsequent acidification produces salicylic acid as the primary product.