Question

Write the mechanism for the acetylation reaction of salicylic acid with acetic anhydride

Answer 1

1. Salicylic acid ionizes to little extend to its salicylate form and hence solution is slightly acidic.
2. The lone pair of electrons on Phenolic OH is available for donation. Hence O of phenolic OH attacks Carboyl carbon of Acetic anahydride.see reaction’s first step.
3. The Carbonyl O get –ve charge.meanwhile O of anhydride get protonated by proton in solution.
4. The reversal of –ve charge on carbonyl O knock out the Acetic acid molecule that could possible now. Drvinging force for this is the generation of neutral and quite stable molecule acetic acid.
5. Hence the Acylation of salicylic acid.