MCAT Organic Chemistry Question 18: Answer and Explanation
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Question: 18
3. Which of the following compounds is optically inactive?
- A.
- B.
- C.
- D.
Correct Answer: C
Explanation:
This answer choice is an example of a meso compound—a compound that contains chiral centers but has an internal plane of symmetry:
Owing to this internal plane of symmetry, the molecule is achiral and, hence, optically inactive. Choices (A) and (B) are enantiomers of each other and will certainly show optical activity on their own. Choice (D), because it contains a chiral carbon and no internal plane of symmetry, is optically active as well.