LECTURE 23 MULTIPULSE

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LECTURE 23MULTI-PULSE MULTI-DIMENSIONAL NMR
TECHNIQUES
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Important NMR Techniques for Structure
Elucidation
For Planer Structure DEPT (distortionless
enhancement by polarization transfer) Identify
protonated carbons ---- CnHm 1H-1H COSY
(Correlated Spectroscopy) Spin system (3J
vicinal coupling) TOCSY (Total Correlation
Spectroscopy) Spin system (amino acid,
protein) HMQC (Heteronuclear Multiple Quantum
Coherence) HSQC (Heteronuclear Single Quantum
Coherence) H-C 1 bond (J 140 Hz) HMBC
(Heteronuclear Multiple Bond Correlation) H-C 2-4
bond (J 8 Hz)
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Important NMR Techniques for Structure
Elucidation
For Relative Structure NOESY (Nuclear Overhauser
Enhancement Spectroscopy) ROESY (Rotating Frame
O. E. S.Y.) Through Space Coupling
Interrelate JS ?S Rapidly make aciculate
assignment Generate Working Structure
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SINGLE PULSE EXPERIMENTS
P170
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SINGLE-PULSE VS. MULTI-PULSE
PREP 90X
DETECTION FID FT
t2
f2 PREP 90X EVOLUTION
MIXING DETECTION FID FT
t1 ?
t2 f2
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MULTI-PULSE EXPERIMENTS
P171
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MULTI-PULSE EXPERIMENTS
THIS IS INVERSION RECOVERY SEE ALSO SPIN-ECHO
P174
P171
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CH3, CH
CH2
P177
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Procedure for Full Structure Elucidation

• MS data
• HRMS --- MF, LRMS --- needs DEPT data CmHnOx
• 2. 1H NMR
• Functional groups --- of Me, OMe, NMe, vinyl
  etc
• 3. Dereplication with MW (MF) and FGs
• Known compound or Unknown
• 4. 13C NMR and DEPT (INEPT or APT)
• Dereplication with MF with FGs
• Known compound or Unknown
• 5. 2D NMR (COSY, HMQC, HMBC)
• Planar Structure --- known or Unknown
• 6. NOESY
• Relative Stereostructure

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Unknown Compound (C10H18O), 1H NMR
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Ipesenol (C10H18O), 13C NMR, DEPT
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Ipesenol (C10H18O), 13C NMR, DEPT
i/CH3
e/CH
b/CH
d/CH2
f/CH2
g/CH2
h/CH
j/Ch3
c/CH2
a/Cq
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Ipesenol (C10H18O), HMQC
C
C
H OH
D

D
G G
F F
B
E
J
I
j h
i
j i
g f e
d c
b
a
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Ipesenol (C10H18O), COSY
I J
CC
H OH
G G
B
D D
FF
E
J I
F, F
F/F
H, OH
H/F, F H/I, J
G G
G/G
E
E/G E/F E/G E/F
C C
D D
LR coupling
B
B/D, B/D
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Ipesenol (C10H18O), HMBC
b
j i h g f e
d c
a
J I
F, F
H, OH
G G
E
C C
D D
B
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SUMMARY

• 2D NMR data, three major experiments (a) 1H-1H
  COSY, (b) 1H -13C COSY (J140), (c) 1H -13C COSY
  (J4-8).
• Major outcomes (a) INTERRELATE JS ?S
  (b) RAPIDLY MAKE ACCURATE ASSIGNMENTS.
• Data acquired by menu-driven multi-pulse
  experiments. Lots of variants.
• Organized approach to spectral interpretation
  (via annotated spectra) is key for 2D data
  presentation.