1. NMR Nuclear Magnetic Resonance Chapter 13

2. Proton Nuclear Spin States Two states have the same energy in the absence of a magnetic field 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 Sample goes in here Coils Insulated tube

11. NMR Signal Proton NMR Spectrum of Cl 3 CH Magnetic Field

12. H HoHo Field here less than H o

13. Electrons shield nucleus from external magnetic field. Magnetic field

14. E =H 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. NMR signal Magnetic Field Cl 3 CH TMS 437 Hz at 60x10 6 Hz

17. Chemical Shift = Position of Signal - Position of TMS Spectrometer Frequency x10 6 Units = parts per million = ppm Chemical Shift Scale = 437 Hz - 0 Hz 60x10 6 Hz x 10 6 = 7.28 ppm

18. Typical Chemical Shifts 0.9 - 1.8 2.1 - 2.5 3.1 - 4.1 2.7 - 4.1 3.3 - 3.7

19. Typical Chemical Shifts 2.3 - 2.8 4.5 - 6.5 6.5 - 8.5 9 - 10 0.5 - 5

20. 10 9 8 7 6 5 4 3 2 1 0 TMSRH Proton Chemical Shifts ppm down field from TMS

23. Area proportional to number of protons

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

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

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

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

29. Adjacent ProtonsLines 123123 234234 n + 1

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

44. What is this compound? CH 3 COCH 2 CH 3

45. C 6 H 5 COCH 3 What is this compound?

46. C 6 H 5 COOCH 2 CH 3

47. y x Magnetic field changes across sample