NMR Nuclear Magnetic Resonance

1
NMR Nuclear Magnetic Resonance

• Proton NMR (and other nuclei)
• Conformational exchange

Index
NMR-basics
H-NMR
NMR-Symmetry
Heteronuclear-NMR
Dynamic-NMR
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Chemical Equivalence by Interconversion
Equivalence in Shift Depends on Temperature,
Solvent, Catalyst

• Keto-Enol Interconversion
• Restricted Rotation (amides)
• Rings InterconversionAxial H -gt equatorial H
• Rapid at room temperature, Slow at 60C

3
Keto-Enol Interconversion
4
Keto-Enol Interconversion
CH3
CH2
CH
CH
Keto CH2
OH enol
5
Keto-Enol Interconversion
CH
CH3
Keto CH2
enol
Keto
6
Restricted Rotation
7
Restricted Rotation
8
Ring Interconversion
9
Ring Interconversion
C-NMR
30oC
Cis-1,4-dimethylcyclohexane
-60oC
10
Ring Interconversion
11
Exchange DNMR Dynamic NMR
NMR is a convenient way to study rate of
reactions provided that the lifetime of
participating species are comparable to NMR time
scale (10-5 s)
At low temperature, hydrogens form an A2B2X spin
system At higher temperature germanium hop from
one C to the next
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Index
NMR-basics
H-NMR
NMR-Symmetry
Heteronuclear-NMR
Dynamic-NMR
NMR and Organometallic compounds