An alcohol is an organic compound containing the –OH functional group. A carboxylic acid is an organic compound containing the –COOH functional group. Alcohols react with carboxylic acids in the presence of an acid catalyst such as concentrated sulfuric acid to form a different type of organic compound called an ester. Many esters are sweet-smelling liquids that are used for making artificial flavours in food and drinks.

Ethanol, for example, reacts with ethanoic acid to form the ester ethyl ethanoate. This process is called esterification.

C₂H₅OH(l) + CH₃COOH(l) ↓  CH₃COOC₂H₅(l) + H₂O(l)

If esters are warmed with dilute acid the esterification process is reversed as the ester reacts with water to re-form the alcohol and carboxylic acid. This process is called hydrolysis. Ethyl ethanoate, for example, forms ethanol and ethanoic acid:

CH₃COOC₂H₅(l) + H₂O(l) ↓ C₂H₅OH(l) + CH₃COOH(l)

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Another word used to describe the hydrolysis of esters is saponification. This is because this type of reaction is used in making soap.

Why is the reaction in which an ester forms an alcohol and a carboxylic acid called hydrolysis?

The reaction is called hydrolysis because it involves the reaction of the ester with water. Other organic reactions that involve reaction with water are also called hydrolysis.

You can learn more about alcohols, carboxylic acids and esters by subscribing to the Carbon chemistry course.