Wednesday, May 12, 2010

Fischer esterification

Fischer esterification involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent:

R1COOH + R2OH is in equilibrium with R1COOR2 + H2O

Strong acids, typically sulfuric acid, catalyze this reaction. Many other acids are also used. Esterification is highly reversible. The yield of the product may be improved using le Chatelier's principle:

* using the alcohol in large excess (i.e. as a solvent),
* using a dehydrating agent. Sulfuric acid not only catalyzes the reaction but sequesters water (a reaction product). Other drying agents like molecular sieves can also be used.
* removal of water by physical means such as distillation as a low-boiling azeotropes with toluene, in conjunction with a Dean-Stark apparatus.

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