VIII. NMR Basic Principles Test

1. Diagram and label the three components of the 1PULSE FT-NMR experiment. Give the parameter names used for the three components in the Unity+300 and VXR-S 400 NMR spectrometers.

2. What is the result when you apply the FT to an FID (time domain signal)?

3. What is the relationship between number of points, spectral width, acquisition time, and digital resolution? Which of these parameters would you change if you wanted better digital resolution, and why? What are the parameter names for number of points, spectral width and acquisition time in the Unity+300 and VXR-S 400NMR spectrometers?

4. What is the peak shape found in most solution NMR spectra?

5. What shim(s) should be adjusted if the peak shape is asymmetrically distorted? Label the shim probably responsible for the distortions below.

6. What is the single best factor to tell whether a sample is poorly shimmed?

7. Given that after 100 transients (8.5 minutes) the S/N for a sample is 25:1 on the Unity+300, and 35:1 on the VXR-S 400, how long will it take to achieve a S/N of 350:1 on each instrument?

8. What are the six factors that can affect the accuracy of a ¹H integration? Why? Are there any additional factors that affect the accuracy of a ¹³C{¹H} integration? Why?

9. When would you use a homonuclear decoupling experiment?

10. Is there a difference between the 1PULSE FT-NMR experiment used to acquire ¹³C{¹H}NMR spectra and that used to acquire ¹H NMR spectra? If yes, what is the difference?