The Kolbe’s reaction (Kolbe–Schmitt reaction) is used to introduce a –COOH group into phenol, mainly at the ortho position.

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Overall reaction

Phenol + NaOH + CO₂ (pressure, heat) → o-hydroxybenzoic acid (salicylic acid)

Key Points

• Reagents: NaOH + CO₂ (high pressure, ~125°C)
• Electrophile: CO₂
• Major product: ortho (salicylic acid)
• Para product is minor
• Ortho favored due to intramolecular H-bonding