MCAT Organic Chemistry Question 99: Answer and Explanation
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Question: 99
9. α-hydrogens of a ketone are acidic due to:
I. resonance stabilization.
II. the electron-withdrawing properties of the alkyl groups.
III. the electronegative carbonyl oxygen.
- A. I only
- B. I and III only
- C. II and III only
- D. I, II, and III
Correct Answer: B
Explanation:
When α-carbons are deprotonated, the negative charge is resonance stabilized in part by the electronegative carbonyl oxygen, which is electron-withdrawing. Alkyl groups are actually electron-donating, which destabilizes carbanion intermediates; this invalidates statement II.