1. NMR
Nuclear
Magnetic
Resonance
Chapter 13

2. Proton Nuclear Spin States
Magnetic
Field
Two states have the same energy in the absence of a magnetic field

3. Protons in an external magnetic field
Energy difference between the spin-states depends on the strength of the magnetic field.

4. NMR Spectrometer

5. Superconducting NMR Magnet

6. NMR Sample Tubes

7. NMR Probe
Coils
Sample goes in here
Insulated tube

11. Proton NMR Spectrum of Cl3CH
Signal
Magnetic Field

12. Field here less than Ho H Ho

13. Electrons shield nucleus from external magnetic field.

14. Energy to change spin state proportional to field strength
E =h
Measure field strength in FREQUENCY units
Cycles/second

15. Tetramethylsilane
TMS
Reference compound for NMR spectrum.

16. Cl3CH
NMR
signal
437 Hz
at 60x106 Hz
TMS
Magnetic Field

17. Chemical Shift Scale = 60x106Hz x106 437 Hz - 0 Hz x 106 = 7.28 ppm
Position of Signal - Position of TMS
x106
Chemical Shift =
Spectrometer Frequency
437 Hz - 0 Hz =
x 106 = 7.28 ppm
60x106Hz
Units = parts per million = ppm

18. Typical Chemical Shifts

19. Typical Chemical Shifts
9 - 10

20. Proton Chemical ShiftsRH
TMS
ppm down field from TMS

22. Sample NMR Spectrum

23. Area proportional to number of protons

24. Number of lines?
How many lines would you expect in the proton NMR spectrum of this compound?

26. Measure signal from this proton
AB Splitting
Field from this proton can be aligned or opposed to applied field
Measure signal from this proton
Magnetic Field

27. Spin Combinations - 2 adjacent protons
-C-CH2- H
1 : 2 : 1

28. Spin Combinations - 3 Adjacent Protons
-C-CH3 H
1: 3: 3: 1

29. Adjacent Protons
Lines 1 2 3 2 3 4
n + 1

31. What is the name of this compound?
Ethyl Bromide

32. NMR Ethyl Bromide

33. NMR Ethyl Acetate

34. NMR Anisaldehyde

35. NMR diethyl ketone

36. NMR i-PrOH

37. NMR n-Propyl iodide

38. Splitting n-PrI

39. Delta = 100 j=10

40. Delta = 49 J=10

41. Delta = 25 J=10

42. Delta=9 J=10

44. MeCOEt
What is this compound?
CH3COCH2CH3

45. What is this compound?
C6H5COCH3

46. What is this compound?
Ethyl Benzoate
C6H5COOCH2CH3

47. MRI y
Magnetic
field changes
across sample x