NMR spectroscopy: chemical shift, spin–spin coupling and relaxation phenomena - Question Bank
1. Which type of nucleus is most susceptible to quadrupolar relaxation, leading to very short relaxation times and often broad signals?
2. In solid-state NMR, which relaxation process is often dominant and leads to very broad signals without special techniques?
3. The phenomenon of 'nuclear Overhauser effect' (NOE) is primarily used to determine:
4. What is the primary difference between T2 and T2* relaxation?
5. The phenomenon of 'spin locking' is related to which relaxation process?
6. Which of the following is NOT a typical relaxation mechanism in NMR?
7. What is 'spin decoupling' in NMR spectroscopy?
8. The intensity of an NMR signal is directly proportional to:
9. A proton in a CH2 group adjacent to a CH3 group will be split into a:
10. A proton in a CH3 group adjacent to a CH2 group will be split into a:
11. What does a broad signal in an NMR spectrum usually indicate?
12. The phenomenon where nuclei in different chemical environments have different resonance frequencies is called:
13. Which nucleus has a spin quantum number of 3/2?
14. What is the typical range for the coupling constant (J) between two vicinal protons (separated by 3 bonds)?
15. Which of the following factors does NOT directly influence the chemical shift of a nucleus?
16. In proton NMR, a signal appearing at 7.2 ppm typically suggests the presence of:
17. What phenomenon causes the splitting of a signal into a doublet of doublets?
18. The relaxation time T2 is also known as:
19. The relaxation time T1 is also known as:
20. Which nucleus is commonly used in NMR and has a spin quantum number of 1/2?
21. The 'second-order effects' in NMR spectra become more pronounced when:
22. A signal that is split into a 1:2:1 ratio is characteristic of coupling to:
23. In a molecule with multiple protons, a signal that appears as a triplet indicates coupling to:
24. The term 'isotropic chemical shift' refers to:
25. What is the effect of increasing the strength of the external magnetic field (B0) on coupling constants (J values)?
26. What is the effect of increasing the strength of the external magnetic field (B0) on chemical shift values?
27. Paramagnetic impurities in an NMR sample typically:
28. In the absence of other relaxation mechanisms, T2 is always:
29. Which relaxation process is responsible for the loss of transverse magnetization?
30. A shorter T2 relaxation time leads to:
31. A shorter T1 relaxation time means:
32. Spin-spin relaxation (T2) describes the process where:
33. Spin-lattice relaxation (T1) describes the process where:
34. What are the two main types of relaxation processes in NMR?
35. Relaxation phenomena in NMR spectroscopy refer to:
36. The coupling between a proton and a 13C nucleus one bond away is denoted as:
37. Which of the following nuclei commonly exhibits spin-spin coupling with protons?
38. When is spin-spin coupling observed across four or more bonds (long-range coupling)?
39. Spin-spin coupling is typically observed between nuclei that are separated by how many bonds?
40. The magnitude of spin-spin coupling is quantified by the coupling constant, J, measured in:
41. A proton coupled to two equivalent neighboring protons will typically appear as a:
42. A proton coupled to one equivalent neighboring proton will typically appear as a:
43. The splitting of an NMR signal into multiple peaks due to spin-spin coupling is often described by the 'n+1 rule'. This rule applies when:
44. What is the primary cause of spin-spin coupling in NMR spectroscopy?
45. Electronegative atoms attached to a carbon atom generally cause a deshielding effect, leading to a chemical shift that is:
46. Nuclei that are shielded by electron density will resonate at a chemical shift that is:
47. In an NMR spectrum, the reference compound tetramethylsilane (TMS) is typically assigned a chemical shift value of:
48. The unit commonly used to express chemical shift in NMR spectroscopy is:
49. In NMR spectroscopy, the 'chemical shift' refers to:
50. What fundamental property of atomic nuclei is exploited in Nuclear Magnetic Resonance (NMR) spectroscopy?