MCAT Organic Chemistry Question 114: Answer and Explanation

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Question: 114

9. In the presence of an acid catalyst, the major product of ethanoic acid and ethanol is:

  • A. acetic anhydride.
  • B. butane.
  • C. diethyl ether.
  • D. ethyl acetate.

Correct Answer: D

Explanation:

The reaction described is esterification, in which the nucleophilic oxygen atom of ethanol attacks the electrophilic carbonyl carbon of ethanoic acid, ultimately displacing water to form ethyl acetate. The acid catalyst is regenerated from ethanol’s released proton. Although acetic anhydride can form via the coupling of two acetic acid molecules, it would not be a major product given the conditions listed in the question, so choice (A) is incorrect. Ethers and alkenes do not form under these conditions either, so choices (B) and (C) are also incorrect.

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