Esterification
A carboxylic acid reacts with an alcohol in the presence of a few drops of concentrated H2SO4 to give an ester and water. Acid chlorides and anhydrides also give esters.
Ethanoic acidCH₃COOHCarboxylic acid - Step 1
CH₃CH₂OH, conc. H₂SO₄ (catalyst), heat
Ethyl ethanoateCH₃COOCH₂CH₃Ester
How it works
- The acid is protonated and the alcohol oxygen attacks the carbonyl carbon.
- Water is lost.
- The ester forms; the reaction is reversible.
What it makes
Esters such as ethyl ethanoate, methyl benzoate and aspirin.
Where it fails
Reversible, so remove water or use excess alcohol. Phenols need acid chlorides or anhydrides.
Class 12, Chapter 8 Aldehydes, Ketones and Carboxylic Acids
Esterification: quick answers
Why is the reaction reversible?
The ester and water can react back to acid and alcohol under the same conditions.
How is the yield raised?
Remove water or use an excess of one reactant.
How is aspirin made?
Salicylic acid is acetylated with acetic anhydride.