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Kuliah NMR 6

Two-dimensional NMR techniques, such as COSY and NOESY, correlate 1H chemical shifts to determine scalar and nuclear Overhauser couplings between protons. COSY identifies protons that are directly bonded, while NOESY identifies proximate protons in 3D space. HMQC and HMBC experiments identify proton-carbon correlations to determine carbon connectivity and distinguish quaternary carbons. These 2D NMR techniques provide detailed structural information about molecules like ethyl acetate, β-ionone, and strychnine.

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Leni Lismayanti
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92 views20 pages

Kuliah NMR 6

Two-dimensional NMR techniques, such as COSY and NOESY, correlate 1H chemical shifts to determine scalar and nuclear Overhauser couplings between protons. COSY identifies protons that are directly bonded, while NOESY identifies proximate protons in 3D space. HMQC and HMBC experiments identify proton-carbon correlations to determine carbon connectivity and distinguish quaternary carbons. These 2D NMR techniques provide detailed structural information about molecules like ethyl acetate, β-ionone, and strychnine.

Uploaded by

Leni Lismayanti
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TWO – Dimensional NMR

The two-dimensional homonuclear (H, H)-corelated NMR experiment


yields NMR spectra in which 1H chemical shifts along both frequency
axes correlated with each other. This technique has become known as
COSY (correlated Spectroscopy).
H,H-COSY (Homonuclear correlation spectroscopy) of Ethyl acetate
COSY - COrrelation SpectroscopY
(correlates scalarly coupled protons)

The gradient DQF-COSY sequence: H3 H4H4 H1 H1 H3 H2 H2

H2
1H
d1 t1 H2

Grad. H3

H1
H1

H H H H H4
1 3 1 3
X X X H4
X O R1
R2 X X X X

H H O H H
2 4 2 4 H3
H,H-COSY of b-Ionone
DQF-COSY of Taxol
(expansion #2)
Known from TOCSY:
F1
6.91, 5.72, 4.72 3.48 (ppm)

4.0
Known from 15N-HSQC: 6.91 is NH
4.5
Known from 13C-HSQC: 3.48 is OH
5.0

X
4.72 5.5

H
55.04 X 6.0

6.91 73.20
HN H 6.5

5.72 OH
3.48
7.0

X O 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5

F2 (ppm)
NOESY (Nuclear Overhauser and Exchange Spectroscopy) of
b-Ionone
H,C-COSY Spectrum of Aphanamol
HMQC (1H-detected-heteronuclear multiple-quantum coherence)
Spectrum of Strychnine
HSQC - Heteronuclear Single Quantum Coherence
Results from the HSQC experiment:
Quaternery
Proton-Carbon Pairs
Carbons
8.06 (2) 130.21 (d*) 4.72 (1) 73.20 (d) 203.61 (s)
7.67 (2) 127.04 (d*) 4.33 (1) 72.18 (d) 172.72 (s)
7.54 (1) 133.71 (d) 4.23 (1); 4.13 (1) 76.52 (t) 171.22 (s)
7.44 (2) 128.70 (d*) 3.73 (1) 45.64 (d) 170.35 (s)
7.42 (1) 131.97 (d) 3.48 (1) 167.04 (s)
7.41 (2) 127.04 (d*) 2.47 (1); 1.81 (1) 35.63 (t) 167.01 (s)
7.35 (2) 129.03 (d*) 2.38 (1) 141.95 (s)
7.33 (2) 128.72 (d*) 2.31 (3) 22.63 (q) 137.99 (s)
7.28 (1) 128.37 (d) 2.29 (1); 2.22 (1) 35.72 (t) 133.65 (s)
6.91 (1) 2.17 (3) 20.84 (q) 133.23 (s)
6.21 (1) 75.57 (d) 1.73 (1) 129.18 (s)
6.16 (1) 72.41 (d) 1.72 (3) 14.83 (q) 81.19 (s)
5.72 (1) 55.04 (d) 1.62 (3) 9.57 (q) 79.05 (s)
5.61 (1) 74.98 (d) 1.17 (3) 26.88 (q) 58.65 (s)
4.87 (1) 84.41 (d) 1.08 (3) 21.83 (q) 43.19 (s)

Conclusions: We have:
a, cross-peaks identify C-H pairs 15 quaternary
b, no cross-peak at a 1H chemical shift: exchangable proton 17 + 6* CH
c, no cross-peak at a 13C chemical shift: quaternary carbon 3 CH2
6 CH3 carbons
Long-range H,C-COSY Spectrum of b-Ionone
HMBC (1H-multilicity bond connectivity) of Strychnine
H
H

COOCH 3
16
OH
H H
3
HO
COOCH 3

NOE COOCH 3
H H
25 26
12 18
24

HO 16
OH
COOCH 3
23
2 O
1
3
OCH3

4 6

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