Question

Write the preparation of salicylic acid with mechanism.

Answer 1

The preparation of salicylic acid by Kolbe-Schmitt reaction:
sodium phenolate (the sodium salt of phenol) is treated with carbon dioxide at 100 atm pressure and 390 K temperature. This is followed by acidification. The mechanism is as shown.
In the first step, hydroxide ion abstracts an acidic proton from phenol to form phenoxide ion. In the next step, phenoxide ion attack C atom of carbon dioxide molecule. Final step is the protonation of carboxylate ion.