MCAT Biochemistry Question 80: Answer and Explanation
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Question: 80
5. For a compound to be aromatic, all of the following must be true EXCEPT:
- A. the molecule is cyclic.
- B. the molecule contains 4n + 2 π electrons.
- C. the molecule contains alternating single and double bonds.
- D. the molecule is planar.
Correct Answer: C
Explanation:
For a compound to be aromatic, it must be cyclic, planar, and conjugated, and contain 4n + 2 π electrons, where n is any integer. Conjugation requires that every atom in the ring have at least one unhybridized p-orbital. While most examples of aromatic compounds have alternating single and double bonds, compounds can be aromatic if they contain triple bonds as well; this would still permit at least one unhybridized p-orbital.