Topic 14 NMR Spectroscopy

Question 1

Which of the following statements about NMR spectroscopy are true? Select all that apply.
A. The area under a peak in an NMR spectrum tells us about the number of atoms experiencing the same chemical environment.
B. NMR spectroscopy can be used to tell us about any elements in a compound.
C. An NMR spectrum tells us about the different isotopes of an element that are present in a compound.
D. NMR spectroscopy exploits light in the radiofrequency region of the electromagnetic spectrum.

Answer 1

A. The area under a peak in an NMR spectrum tells us about the number of atoms experiencing the same chemical environment.
D. NMR spectroscopy exploits light in the radiofrequency region of the electromagnetic spectrum.

Question 2

The position of a peak in a 13C-NMR spectrum tells us information about which of the following?
A. The molecular mass of the sample being studied.
B. The atoms immediately surrounding a carbon atom.
C. The number of carbon atoms present in the sample.
D. The electrical charge carried by the sample.
E. The 3D structure of the sample being studied.

Answer 2

B. The atoms immediately surrounding a carbon atom.

Question 3

4 factors for determining the chemical structure from H-NMR spectra

Answer 3

1. number of peaks = number of different protons in a sample
2. chemical shift = function of the electronic environment of a proton
3. integration = the area under the peak -> gives the ratio of the number of equivalent protons
4. Splitting pattern = gives information about the nearest-neighbour protons. n+1 peaks