NMR Nuclear Magnetic Resonance

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NMR Nuclear Magnetic Resonance

• Special NMR topics

Index
NMR-basics
H-NMR
NMR-Symmetry
Heteronuclear-NMR
Dynamic-NMR
NMR / Organometallic compounds
Special 1D-NMR
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Inversion Recovery
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Dinitrobenzene T1
H4/H6
H2
H5
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Inversion recovery 13C
t 50 s
D1 5T1
t 6 s
t 3 s
t 1.5 s
t 0.03 s
T1 tnull / ln2 1.443 tnull
e.g. C2 gt T1 4.3 s (tnull3 )
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Helping relaxation
One approach of reducing relaxation time is by
the addition of paramagnetic relaxation reagent
(Chromium III acetylacetonate gt Cr(acac)3)
With Cr(acac)3
1s delay, 30o pulse Without Cr(acac)3
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Refocusing of field inhomogeneity
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CPMG used to get rid of broad signals
90
180
t
Polystyrene (50,000) camphor
t 1.5 ms
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Heteronuclear Decoupling
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Heteronuclear nOe
For nuclei having positive g (e.g.
13C) Decoupling proton can produce higher
signals due to nOe. Enhancement is dependant on
motion and distance between interacting nuclei
As a consequence, quaternary carbons are much
smaller than protonated carbons
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Heteronuclear nOe

• Can yield higher positive signal for nuclei with
  positive g (e.g. 13C)
• For nuclei with negative g (e.g. 29Si, 15N) can
  yield larger (negative) signals or for partial
  T1DD can null the signal!!!

e.g. 15N 1H
S A0NOE -4
S A0NOE 0
S A0NOE -1.5
50 NOE
20 NOE
Without NOE S A0 1
100 NOE
NOE-1
NOE-2.5
gH
-5
NOEmax ?
2 gN
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APT Pulse Sequence
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Multiplet Modulation
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APT 8 msec delay
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APT 6 msec delay
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INEPT
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Comparing NOE Enhancement and INEPT Enhancement
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INEPT sequence
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Multiplet distortion in INEPT 29Si
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Multiplet distortion in coupled INEPT 13C
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Multiplet distortion in coupled INEPT 13C
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29Si INEPT coupled
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Refocused INEPT
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Multiplicity Modulation HX
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Multiplicity Modulation XH2
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Multiplicity Modulation XH3
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Decoupled INEPT Menthol
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Optimum delay in decoupled INEPT
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Decoupled INEPT compare normal and INEPT 29Si
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DEPT
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Intensity vs pulse angle
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Menthol in Acetone-d6
DEPT-135
DEPT-90
DEPT-90
DEPT-45
Normal 13C
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DEPT Ipsenol
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DEPT Editing
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ADEPT Editing
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Index
NMR-basics
H-NMR
NMR-Symmetry
Heteronuclear-NMR
Dynamic-NMR
NMR and Organometallic compounds
Special 1D-NMR
IR-basics