Acid to Ester (Fischer Esterification)

Reaction, Reagents
& Mechanism

Reaction & Reagents info

  • Fischer Esterification: It involves the conversion of acid to esters under acidic conditions
  • It is a reversible reaction. In order to push the reaction to the forward reaction, a large excess of alcohol is used and the by-product (water) is removed by azeotropic distillation

Advantages

  • Inexpensive oxidation method on manufacturing scale

Disadvantages

  • It is useful, only if alcohol is inexpensive and commercially available.
  • The reaction is reversible and rate of the reaction is slow

Useful Links on Reagent & Reaction:


For review papers and other articles, 
refer to the tab "References"

Mechanism

Additional details

Scheme & Procedure

General Procedure:

To a solution of carboxylic acid (1 eq.) in alcohol (10 Vol) at 0 oC is added few drops of Conc. H2SO4 (about 5 drops) and stirred at room temperature for 4 h. The reaction is monitored by TLC. If the reaction does not proceed, it shall be refluxed for 4 to 6 h. After the completion of the reaction, the reaction mixture is distilled off and diluted with DCM or EtOAc. The organic layer is then successively washed with water (10 Vol x 2), and brine solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is purified by column chromatography

Note:

  • This reaction is very useful, if alcohol is inexpensive and commercially available. Methyl and Ethyl esters could be prepared easily by this method
  • In place of Conc. H2SO4, PTSA could also be used
  • This reaction is in equilibrium, though is more favoured. Water (i.e. moisture) tends to hydrolyze the ester back to acid. In order to drive it to the forward reaction, high-temperature reflux, Dean-Stark apparatus and molecular sieves are usually used

For more details on reactions and reagents, 
refer to the tab "Reaction, Reagents and Mechanism"

Typical Procedure:

For more details on large-scale reactions and OPRD procedures, 
refer to the tab "Scale-up & Green Chem"

Patent references

Scale-up &
Green Chem.

  • Fischer esterification is very useful, if alcohol is inexpensive and commercially available. Methyl and Ethyl esters could be prepared easily by this method on manufacturing scale.
  • In place of Conc. H2SO4, PTSA could also be used

Scale-Up Typical Procedure:

Reaction Tree

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