Exam Practice

Report
NMR - The
Coupling Constant
4-1
ASSIGNMENT OF SPIN SYSTEMS
For each compound:
Describe all spin systems
Determine the number of
protons that are:
• Chemical shift equivalent
• Magnetic equivalent
• Enantiotopic
• Diastereotopic
CHEM 430 – NMR Spectroscopy
1
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 114
MW 116
CHEM 430 – NMR Spectroscopy
2
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 169
has -Br
MW 150
CHEM 430 – NMR Spectroscopy
3
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 100
MW 74
CHEM 430 – NMR Spectroscopy
4
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 73
MW 56
CHEM 430 – NMR Spectroscopy
5
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 89
MW 138
CHEM 430 – NMR Spectroscopy
6
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 122
MW 102
CHEM 430 – NMR Spectroscopy
7
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 113
MW 94
CHEM 430 – NMR Spectroscopy
8
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 152
MW 157
has -Cl
CHEM 430 – NMR Spectroscopy
9
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 208
MW 98
CHEM 430 – NMR Spectroscopy
10
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 126
MW 116
CHEM 430 – NMR Spectroscopy
11
NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 162
2 -Cl
MW 122
CHEM 430 – NMR Spectroscopy
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NMR - The
Coupling Constant
4-1
SPLITTING OF SIGNALS – STRUCTURE DETERMINATION
MW 96
CHEM 430 – NMR Spectroscopy
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NMR - The
Coupling Constant
4-1
PRACTICE WITH POPLE NOTATION
On graph paper, draw a schematic (line) representation of the pure firstorder spectrum AMX3 corresponding to the following parameters:
n (Hz from TMS): nA = 80; nM = 220; nX = 320
J (Hz): JAM = 10; JAX = 12; JMX = 0
• Assume spectrum is a pure 1st order spectrum and ignore small
distortions in relative intensities that would occur in a ‘real’ spectrum.
• Sketch in “splitting diagrams” above the schematic spectrum to
indicate which splittings correspond to which coupling constants.
• Give the shifts on the d scale corresponding to the above spectrum on a
60 MHz NMR (1H).
CHEM 430 – NMR Spectroscopy
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NMR - The
Coupling Constant
4-1
PRACTICE WITH POPLE NOTATION
AMX3
n (Hz from TMS): nA = 80; nM = 220; nX = 320
J (Hz): JAM = 10; JAX = 12; JMX = 0
CHEM 430 – NMR Spectroscopy
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NMR - The
Coupling Constant
4-1
STRUCTURE DETERMINATION WITH POPLE NOTATION
The 400 MHz 1H NMR spectrum of
one of the following isomeric
hydroxycinnamic acids is given below.
Which one is it? Justify your answer
based on chemical shift and coupling
constants.
CHEM 430 – NMR Spectroscopy
16
NMR - The
Coupling Constant
4-1
STRUCTURE DETERMINATION WITH POPLE NOTATION
CHEM 430 – NMR Spectroscopy
17

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