MCAT Organic Chemistry Question 16: Answer and Explanation
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Question: 16
1. Which of the following does NOT show optical activity?
- A. (R)-2-butanol
- B. (S)-2-butanol
- C. A solution containing 1 M (R)-2-butanol and 2 M (S)-2-butanol
- D. A solution containing 2 M (R)-2-butanol and 2 M (S)-2-butanol
Correct Answer: D
Explanation:
This is a racemic mixture of 2-butanol because it consists of equimolar amounts of (R)-2-butanol and (S)-2-butanol. The (R)-2-butanol molecule rotates the plane of polarized light in one direction, and the (S)-2-butanol rotates it by the same angle but in the opposite direction; as a result, no net rotation of polarized light is observed.