MCAT Organic Chemistry Question 59: Answer and Explanation

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Question: 59

14. Aldehydes are generally more reactive than equivalent ketones to nucleophiles. This is likely due to differences in:

  • A. steric hindrance.
  • B. leaving-group ability.
  • C. resonance stabilization.
  • D. electron-withdrawing character.

Correct Answer: A

Explanation:

Aldehydes have one alkyl group connected to the carbonyl carbon, whereas ketones have two. This creates more steric hindrance in ketones, which lowers their reactivity to nucleophiles. Ketones are also less reactive because their carbonyl carbon has less positive charge character; the additional alkyl group can donate electron density—the opposite of choice (D)—which decreases the electrophilicity of the compound.

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