Acidic hydrolysis is simply the reverse of esterification. The ester is heated with a large excess of water containing an acid catalyst. Like esterification, the reaction is reversible and does not go to completion.

As a specific example, butyl acetate and water react to form acetic acid and 1-butanol.

(Note: Butyl acetate should have one more CH₂ in the green part,  Also, the second to the last C in the green part should be CH₂ not CH₃.   MK)

Example 7

Write an equation for the acidic hydrolysis of ethyl butyrate (CH₃CH₂CH₂COOCH₂CH₃) and name the products.

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In acidic hydrolysis, water (HOH) splits the ester bond. The H of HOH joins to the oxygen atom in the OR part of the original ester, and the OH of HOH joins to the carbonyl carbon atom:

The products are butyric acid (butanoic acid) and ethanol.

When a base (such as sodium hydroxide [NaOH] or potassium hydroxide [KOH]) is used to hydrolyze an ester, the products are a carboxylate salt and an alcohol. Because soaps are prepared by the alkaline hydrolysis of fats and oils, alkaline hydrolysis of esters is called saponification from the Latin sapon, meaning “soap,” and facere, meaning “to make”. In a saponification reaction, the base is a reactant, not simply a catalyst. The reaction goes to completion:

As a specific example, ethyl acetate and NaOH react to form sodium acetate and ethanol:

Example 8

Write an equation for the hydrolysis of methyl benzoate in a potassium hydroxide solution.

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In basic hydrolysis, the molecule of the base splits the ester linkage. The acid portion of the ester ends up as the salt of the acid (in this case, the potassium salt). The alcohol portion of the ester ends up as the free alcohol.