Hydrolysis of Esters

Hydrolysis of an ester means splitting it by reaction with water. It is the reverse of esterification and can be done with an acid or an alkali, giving different products.Acid hydrolysis. The ester is heated under reflux with dilute acid (such as dilute sulfuric or hydrochloric acid), which acts as a catalyst. The products are a carboxylic acid and an alcohol. The reaction is reversible, so it does not go to completion; an excess of water pushes the equilibrium to the right.CH₃COOCH₂CH₃ + H₂O ⇌ CH₃COOH + CH₃CH₂OHAlkaline (base) hydrolysis. The ester is heated under reflux with aqueous sodium hydroxide. The products are the salt of the carboxylic acid (a carboxylate) and an alcohol.CH₃COOCH₂CH₃ + NaOH → CH₃COONa + CH₃CH₂OHThis reaction goes to completion because the carboxylate ion formed does not react with the alcohol, so the reverse reaction cannot happen. To obtain the free carboxylic acid, the mixture is then acidified with a strong acid such as dilute hydrochloric acid.Example: heating methyl propanoate with NaOH(aq) gives sodium propanoate and methanol; with dilute acid it gives propanoic acid and methanol.