ASSIGNMENT OF SPIN SYSTEMSNMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

1

For each compound:

Describe all spin systems

Determine the number of protons that are: • Chemical shift equivalent• Magnetic equivalent • Enantiotopic• Diastereotopic

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 114

MW 116

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

3

MW 169has -Br

MW 150

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

4

MW 100

MW 74

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 73

MW 56

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

6

MW 89

MW 138

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 122

MW 102

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 113

MW 94

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 152

MW 157has -Cl

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 208

MW 98

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 126

MW 116

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

12

MW 1622 -Cl

MW 122

SPLITTING OF SIGNALS – STRUCTURE DETERMINATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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MW 96

PRACTICE WITH POPLE NOTATIONNMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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On graph paper, draw a schematic (line) representation of the pure first-order spectrum AMX3 corresponding to the following parameters: 

n (Hz from TMS): nA = 80; nM = 220; nX = 320J (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).

PRACTICE WITH POPLE NOTATIONNMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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AMX3

n (Hz from TMS): nA = 80; nM = 220; nX = 320J (Hz): JAM = 10; JAX = 12; JMX = 0

 

STRUCTURE DETERMINATION WITH POPLE NOTATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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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.

STRUCTURE DETERMINATION WITH POPLE NOTATION

NMR - The Coupling Constant 4-1

CHEM 430 – NMR Spectroscopy

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