Kolbe–Schmitt reaction

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"Kolbe process" redirects here. For the electrochemical decarboxylation/dimerization reaction, see Kolbe electrolysis.
Kolbe–Schmitt reaction
Named after Hermann Kolbe
Rudolf Schmitt
Reaction type Addition reaction
Organic Chemistry Portal kolbe-schmitt-reaction
RSC ontology ID RXNO:0000182

The Kolbe–Schmitt reaction or Kolbe process (named after Hermann Kolbe and Rudolf Schmitt) is a carboxylation chemical reaction that proceeds by heating sodium phenoxide (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).[1][2][3]

The Kolbe–Schmitt reaction

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

Reaction mechanism[edit]

The Kolbe–Schmitt reaction proceeds via the nucleophile addition of a phenoxide, classically sodium phenoxide (NaOC6H5), 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


External links[edit]

  • [1] English Translation of Kolbe's seminal 1860 German article in Annalen der Chemie und Pharmacie that describes the discovery of this reaction. English title: 'On the syntheses of salicylic acid'; German title "Ueber Synthese der Salicylsäure".
  • [2] An animation of the reaction mechanism.