MCAT Organic Chemistry Question 153: Answer and Explanation
Home > MCAT Test > MCAT organic chemistry practice tests
Test Information
- Use your browser's back button to return to your test results.
- Do more MCAT organic chemistry practice tests.
Question: 153
3. If IR spectroscopy were employed to monitor the oxidation of benzyl alcohol to benzaldehyde, which of the following would provide the best evidence that the reaction was proceeding as planned?
- A. Comparing the fingerprint region of the spectra of starting material and product
- B. Noting the change in intensity of the peaks corresponding to the benzene ring
- C. Noting the appearance of a broad absorption peak in the region of 3100–3500 cm–1
- D. Noting the appearance of a strong absorption in the region of 1750 cm–1
Correct Answer: D
Explanation:
In this reaction, the functional group is changing from a hydroxyl to an aldehyde. This means that a sharp peak will appear around 1750 cm–1, which corresponds to the carbonyl functionality. Choice (C) is the opposite of what occurs; the reaction will be characterized by the disappearance of the O–H peak at 3100 to 3500 cm–1, not its appearance. Comparing the fingerprint regions, as in choice (A), will provide evidence that a reaction is occurring, but is not as useful for knowing that the reaction that occurred was indeed the one that was desired.