What is the Kolbe-Schmitt reaction?

The Kolbe-Schmitt reaction is a chemical process in which sodium phenoxide reacts with carbon dioxide under pressure to form salicylic acid, a key step in making aspirin.

In this reaction, phenol is first converted into sodium phenoxide by reacting with sodium hydroxide. Then, carbon dioxide gas is passed through this compound at about 125°C and 5–7 atmospheres of pressure.

The intermediate product is sodium salicylate, which upon acidification with hydrochloric acid yields salicylic acid. This reaction is important in organic chemistry and pharmaceutical manufacturing, especially for producing aspirin and dyes. The process demonstrates electrophilic substitution in aromatic chemistry and highlights how phenol derivatives react under controlled conditions.

Chemical equations

 C₆H₅ONa + CO₂ → C₆H₄(OH)COONa C₆H₄(OH)COONa + HCl → C₆H₄(OH)COOH + NaCl