O Levels Chemistry (5070)•5070/11/M/J/21
Explanation
Esterification: Carboxylic acid + alcohol → ester Steps:
- Parse ester formula CH3COOC2H5: acyl group CH3COO- from ethanoic acid (CH3COOH); alkyl group C2H5- from ethanol (C2H5OH).
- Recall reaction: RCOOH + R'OH → RCOOR' + H2O (Fischer esterification).
- Match R = CH3 (ethanoic acid) and R' = C2H5 (ethanol).
- Confirm pair: ethanoic acid and ethanol produce CH3COOC2H5.
Why A is correct:
- Ethanoic acid provides CH3COO-; ethanol provides -C2H5, forming exact ester per esterification formula.
Why the others are wrong:
- B: Propanol (C3H7OH) and propanoic acid (C2H5COOH) form C2H5COOC3H7 (propyl propanoate).
- C: Ethanol (C2H5OH) and propanoic acid (C2H5COOH) form C2H5COOC2H5 (ethyl propanoate).
- D: Propanol (C3H7OH) and ethanoic acid (CH3COOH) form CH3COOC3H7 (propyl ethanoate).
Final answer: A
Topic: Formulae, functional groups and terminology
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