Fischer esterification

Fischer esterification is the process of forming an ester by refluxing a carboxylic acid and an alcohol in the presence of an acid (catalyst).

Acid catalysts

Commonly used acid catalysts for a Fischer esterification include:

• Sulfuric acid

Mechanism

1. Proton transfer from acid catalyst to carbonyl oxygen increases electrophilicity of carbonyl carbon.
2. The carbonyl carbon is attacked by the nucleophilic oxygen atom of the alcohol.
3. Formation of an oxonium ion.
4. Proton transfer from the oxonium ion to a second molecule of alcohol gives a TCAC
5. Proton transfer from one of the hydroxyl groups of the TCAC gives a new oxonium ion.
6. Loss of water from this oxonium ion gives the ester and water

Examples

• The formation of benzocaine.