Which of the following reactions represents the hydrolysis of an alkanoate?

Analyze the question: Hydrolysis of an alkanoate (an ester) means the ester reacts with water to break down into its parent carboxylic acid and alcohol. With an acid catalyst (H⁺), the reaction is reversible.

Concept: RCOOR' + H₂O ⇌ (H⁺) RCOOH + R'OH

This is the reverse of esterification (Fischer esterification).

Check each option:

• A. CH₃COOH + OH⁻ → CH₃COO⁻ + H₂O is a neutralisation (acid-base) reaction, not hydrolysis.
• B. CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O is esterification, the formation of an ester. This is the reverse of hydrolysis.
• C. CH₃COOC₂H₅ + H₂O → CH₃COO⁻ + CH₃CH₂OH starts with an ester and water, but the product is the carboxylate ion. That is characteristic of alkaline hydrolysis (saponification, with OH⁻), not the acid-catalysed pathway shown with H⁺. It is also not balanced for charge, since the H⁺ is not accounted for. So it is not the best representation.
• D. CH₃COOCH₂CH₃ + H₂O ⇌ (H⁺) CH₃COOH + CH₃CH₂OH takes ethyl ethanoate plus water and gives ethanoic acid and ethanol. This is a correct, balanced acid-catalysed hydrolysis of an ester.

Tip: Remember "ester + water → acid + alcohol" for hydrolysis, and "acid + alcohol → ester + water" for esterification. If the ester is hydrolysed with a base (NaOH), you get the carboxylate salt and alcohol instead, and this is called saponification.