Kolbe-Schmitt reaction

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The Kolbe-Schmitt reaction/Kolbe process (named after Adolph Wilhelm Hermann Kolbe and R. Schmitt) is a carboxylation chemical reaction that proceeds by heating sodium phenolate (the sodium salt of phenol) with carbon dioxide under pressure (100 atm, 125°C), then treating the product with sulfuric acid. The final product is an aromatic hydroxy acid which is also known as salicylic acid (the precursor to aspirin).

The Kolbe-Schmitt reaction

By using the potassium salt 4-hydroxybenzoic acid is accessible, an important precursor for the versatile paraben class of biocides used e.g. in personal care products.

[edit] Reaction mechanism

The Kolbe-Schmitt reaction proceeds via the nucleophilic addition of a phenolate to carbon dioxide to give the salicylate. The final step is reaction of the salicylate with acid to form the desired salicylic acid.

Kolbe-Schmitt reaction mechanism

[edit] References

  • Kolbe, H. Ann. 1860, 113, 125.
  • Schmitt, R. J. Prakt. Chem. 1885, [2] 31, 397.
  • Lindsey, A. S.; Jeskey, H. Chem. Rev. 1957, 57(4), 583-620. (Review)
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