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NMR

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Nuclear Magnetic Resonance Chapter 13 Proton Nuclear Spin States Protons in an external magnetic field NMR Spectrometer Superconducting NMR Magnet NMR Sample Tubes ... – PowerPoint PPT presentation

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Title: NMR


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
8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
Proton NMR Spectrum of Cl3CH
NMR Signal
Magnetic Field
12
Field here less than Ho
H
Ho
13
Electrons shield nucleus from external magnetic
field.
Magnetic field
14
Energy to change spin state proportional to field
strength
E
H
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

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
0.9 - 1.8
2.7 - 4.1
2.1 - 2.5
3.3 - 3.7
3.1 - 4.1
19
Typical Chemical Shifts
2.3 - 2.8
9 - 10
4.5 - 6.5
0.5 - 5
6.5 - 8.5
20
Proton Chemical Shifts
TMS
RH
10 9 8 7 6 5 4
3 2 1 0
ppm down field from TMS
21
(No Transcript)
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?
25
(No Transcript)
26
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

30
(No Transcript)
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 j10
40
Delta 49 J10
41
Delta 25 J10
42
Delta9 J10
43
(No Transcript)
44
MeCOEt
What is this compound?
CH3COCH2CH3
45
What is this compound?
  • C6H5COCH3

46
Ethyl Benzoate
What is this compound?
C6H5COOCH2CH3
47
MRI
y
Magnetic field changes across sample
x
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