1. 13. Structure Determination: Nuclear Magnetic Resonance Spectroscopy
Based on McMurry’s Organic Chemistry, 7th edition

2. Analyzing organic compounds
Proof of identity

3. Kcal/mol
1.7 X 103
5.7 X 105
9.5 X 103
4.8 X 102 72
1.2
9.5 X 10-3
10-4
EIMS
NMR

4. The Nobel Prize in Physics 1952
"for their development of new methods for nuclear magnetic precision measurements and discoveries in connection therewith "
Felix Bloch
Edward Mills Purcell

5. Figure 13.1: (a) Nuclear spins are oriented randomly in the absence of an external magnetic field but (b) have a specific orientation in the presence of an external field, B0. Some of the spins (red) are aligned parallel to the external field while others (blue) are antiparallel. The parallel spin state is slightly lower in energy and therefore favored.
Fig. 13-1, p. 441

6. Figure 13.2: Dependence of the difference in energy between lower and higher nuclear spin levels of the hydrogen atom
Nuclei in different environments (i.e. with different amounts of electron density around them) will require different amounts of energy to “flip” to higher energy different spin state

7. Table 13-1, p. 442

8. Figure 13. 4: Schematic operation of an NMR spectrometer
Figure 13.4: Schematic operation of an NMR spectrometer. A thin glass tube containing the sample solution is placed between the poles of a strong magnet and irradiated with rf energy.
Fig. 13-4, p. 444

9. Old School:
Continuous wave (CW)
40 MHz NMR spectrometer
1960

10. Continuous wave (CW) 60 MHz NMR spectrum
1964
Old School:
Continuous wave (CW) 60 MHz NMR spectrum

11. Not so old: 1980’s
60 MHz

12. Yokohama City University 500 MHz NMR spectrometer
Northern Kentucky University

13. The Nobel Prize in Chemistry 1991
"for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy"
Richard R. Ernst

14. Free-induction decay data and proton-decoupled 13C nuclear magnetic resonance spectra

15. 13C NMR spectrum 1-pentanol : 1 scan 1-pentanol : 200 scans
Fig. 13-6, p. 447
13C NMR spectrum
1-pentanol : 1 scan
1-pentanol : 200 scans
Figure 13.6: Carbon-13 NMR spectra of 1-pentanol, CH3CH2CH2CH2CH2OH. Spectrum (a) is a single run, showing the large amount of background noise. Spectrum (b) is an average of 200 runs.

16. 13.3 The Nature of NMR Absorptions
1H NMR spectrum
13C NMR spectrum

17. The Nobel Prize in Chemistry 2002
"for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution"
Kurt Wüthrich

18. The Nobel Prize in Medicine 2003
"for their discoveries concerning magnetic resonance imaging "
Paul C. Lauterbur
Sir Peter Mansfield

19. More energy to flip nucleus
Less energy to flip nucleus
d, ppm
chemical shift

20. Information in a 13C NMR spectrum

21. sp3
Figure 13.7: Chemical shift correlations for 13C NMR.
77 ppm
CDCl3
Fig. 13-7, p. 448

23. Figure 13.10: DEPT–NMR spectra for 6-methyl-5-hepten-2-ol.
Part (a) is an ordinary broadband-decoupled spectrum, which shows signals for all eight carbons.
Fig a, p. 451

24. Information in a 1H NMR spectrum
13C NMR spectrum

25. Table 13-2, p. 457

26. 6.5 – 8.0
Table 13-3, p. 458

27. C6H12O2

28. Figure 13. 13: The 1H NMR spectrum of bromoethane, CH3CH2Br
Figure 13.13: The 1H NMR spectrum of bromoethane, CH3CH2Br. The –CH2Br protons appear as a quartet at 3.42δ, and the –CH3 protons appear as a triplet at 1.68δ.
Fig , p. 460

29. Figure 13. 13: The 1H NMR spectrum of bromoethane, CH3CH2Br
Figure 13.13: The 1H NMR spectrum of bromoethane, CH3CH2Br. The –CH2Br protons appear as a quartet at 3.42δ, and the –CH3 protons appear as a triplet at 1.68δ.
Fig , p. 460

30. C3H7Br

31. Figure 13. 19: The 1H NMR spectrum of trans-cinnamaldehyde
Figure 13.19: The 1H NMR spectrum of trans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaks—a doublet of doublets—by the two nonequivalent neighboring protons.
Fig , p. 466

32. Figure 13. 19: The 1H NMR spectrum of trans-cinnamaldehyde
Figure 13.19: The 1H NMR spectrum of trans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaks—a doublet of doublets—by the two nonequivalent neighboring protons.
Fig , p. 466

33. C10H12O

35. 3H 2H
C10H12O2 3H 2H 2H