MCAT Organic Chemistry Question 154: 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: 154

4. Which of the following chemical shifts could correspond to an aldehydic proton signal in a ¹H–NMR spectrum?

A. 9.5 ppm
B. 7.0 ppm
C. 11.0 ppm
D. 1.0 ppm

Correct Answer: A

Explanation:

The peak at 9.5 ppm corresponds to an aldehydic proton. This signal lies downfield because the carbonyl oxygen is electron-withdrawing and deshields the proton. Choice (C) corresponds to a carboxyl proton and is even further downfield because the acidic proton is deshielded to a greater degree than the aldehyde proton. Choice (B) corresponds to aromatic protons. Choice (D) is characteristic of an alkyl proton on an sp³-hybridized carbon.

Previous Next