Kcal/mol

1
Kcal/mol
1.7 X 103
5.7 X 105
9.5 X 103
4.8 X 102
9.5 X 10-3
1.2
72
10-4
EIMS
NMR
2
Nuclear Magnetic Resonance (NMR) Spectroscopy
To here!
From here
3
The Nobel Prize in Physics 1952
"for their development of new methods for nuclear
magnetic precision measurements and discoveries
in connection therewith "
4

• Magnetic nuclei are in resonance with external
  magnetic field if they absorb energy and
  spin-flip from low energy state (parallel
  orientation) to high energy state (antiparallel
  orientation).

5
atomic nuclei in absence of magnetic field
atomic nuclei in presence of external magnetic
field
atomic nuclei can either align parallel (lower E)
or antiparallel (higher E)
6

• Magnetic nuclei are in resonance with external
  magnetic field if they absorb energy and
  spin-flip from low energy state (parallel
  orientation) to high energy state (antiparallel
  orientation).

7
Dependence of the difference in energy between
lower and higher nuclear spin levels of the
hydrogen atom
8
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
9

• Magnetic
• All nuclei with odd number of protons
• All nuclei with odd number of neutrons
• Nonmagnetic
• Nuclei with even number of both protons and
  neutrons

10

Fig. 13-4, p. 444
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Really Old School Continuous wave (CW) 40 MHz
NMR spectrometer
1960
13
1964
A little less old school Continuous wave (CW)
60 MHz NMR spectrum
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Not quite so old school 1980s 60 MHz
15
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
16
State-of-the-art
900 MHz NMR spectrometer Center for Biomolecular
NMR, Heinrich-Heine-Universität Düsseldorf
17
Colchitaxel, a coupled compound made from
microtubule inhibitors colchicine and paclitaxel
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Free-induction decay data and proton-decoupled
13C nuclear magnetic resonance spectra
19

20

21
The Nature of NMR Absorptions
1H NMR spectrum
13C NMR spectrum
22
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
23
The Nobel Prize in Medicine 2003
"for their discoveries concerning magnetic
resonance imaging "
24
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Magnetically distinct 13C NMR of methyl acetate
Chemically equivalent nuclei always show the same
absorption
26
Magnetically distinct hydrogens and carbons!
27

77 ppm CDCl3
Fig. 13-7, p. 448
28

sp3
77 ppm CDCl3
Fig. 13-7, p. 448
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• For each molecule below
• Determine the number of distinct carbon peaks
• Assign chemical shifts for each distinct carbon

32

Fig. 13-10a, p. 451
33
Information in a 1H NMR spectrum
1H NMR spectrum
13C NMR spectrum
34

Table 13-2, p. 457
35

Table 13-3, p. 458
36

6.5 8.0
Table 13-3, p. 458
37
1H NMR Integration
Area under each peak is proportional to number of
protons causing that peak.
Gives ratio, not always exact number!
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spin-spin splitting
39
Spin Spin Splitting
Absorption of a proton can split into multiple
peaks (multiplet)
Tiny magnetic field produced by one nucleus
affects magnetic field felt by neighboring nuclei
Fig. 11-13, p. 424
40

Fig. 13-13, p. 460
41

Chemical shift middle of multiplet
3.4130
3.4165
3.4270
3.4235
d 3.42
Fig. 13-13, p. 460
42
Common NMR splitting patterns
43
C3H7Br
Fig. 11-15, p. 425
44
12
C3H7Br
2
Fig. 11-15, p. 425
45
1.5
C10H12O2
1
1.5
1
1
Fig. 11-16, p. 427
46
C10H12O
4.5
4.5
3
3
3
47

Fig. 13-19, p. 466
48

Fig. 13-19, p. 466
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p. 409