MCAT Organic Chemistry Question 157: Answer and Explanation
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Question: 157
7. Compared to IR and NMR spectroscopy, UV spectroscopy is preferred for detecting:
- A. aldehydes and ketones.
- B. unconjugated alkenes.
- C. conjugated alkenes.
- D. aliphatic acids and amines.
Correct Answer: C
Explanation:
Most conjugated alkenes have an intense ultraviolet absorption. Aldehydes, ketones, acids, and amines, mentioned in choices (A) and (D), all absorb in the ultraviolet range. However, other forms of spectroscopy (mainly IR and NMR) are more useful for precise identification. Isolated alkenes, choice (B), can rarely be identified by UV.