How can Fischer esterification equilibrium be shifted to produce more ester?

Question

Paisley Boney · Accepted Answer

You can shift a Fischer esterification in the product direction either by (a) using a large excess of one reactant or (b) by removing one of the products.

The equation for a Fischer esterification is

#"RCOOH + R'OH" stackrelcolor (blue)("acid")(⇌) "RCOOR'" + "H"_2"O"#

According to Le Châtelier's Principle, we can shift the position of equilibrium to the right either by adding an excess of a reactant or by removing one of the products.

Adding an excess reactant

If we use a large excess of one reactant (usually the cheaper one!), we can push the position of equilibrium to the side that produces more ester.

Removing one of the products

If the ester is insoluble in water (and it usually is), the ester and the water will form two separate layers.

You can then use a Dean-Stark trap to collect the water and prevent it from returning to the reaction mixture.

The video below shows how to use a Dean-Stark trap to separate water from toluene, but you can also use it to separate the water from an esterification reaction.

Ryan Andrews · Answer

undefined To shift the Fischer esterification equilibrium to produce more ester, you can:
- Increase the concentration of the alcohol and carboxylic acid reactants.
- Use a dehydrating agent such as sulfuric acid to remove water from the reaction mixture.
- Remove the formed ester from the reaction mixture, which helps drive the equilibrium towards the product side according to Le Chatelier's principle.
- Use an excess of one of the reactants, typically the alcohol, to drive the equilibrium towards the ester formation.