A Levels Chemistry (9701)•9701/12/M/J/24
Explanation
Ester Hydrolysis Yields Carboxylic Acid from Acyl Group
Steps:
- Identify the acyl (RCO-) group in each ester structure, as hydrolysis cleaves the ester bond to produce RCOOH and alcohol.
- For ester X, the acyl group is CH3CH2CO-, yielding CH3CH2COOH (propanoic acid).
- For ester Y, the acyl group is CH3CH2CH2CO-, yielding CH3CH2CH2COOH (butanoic acid).
- Match the pair of acids to the options.
Why B is correct:
- Acid hydrolysis of esters follows the reaction RCOOR' + H2O → RCOOH + R'OH, where the carboxylic acids match the acyl groups in X (propanoate) and Y (butanoate).
Why the others are wrong:
- A: Incorrectly assigns acetic acid to X, which has propanoyl group.
- C: Swaps the acids, assigning butanoic to X and acetic to Y.
- D: Assigns butanoic acid to both, ignoring X's propanoyl group.
Final answer: B
Topic: Carboxylic acids and derivatives
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