C8953
NMR structural analysis - seminar
Vector model of NMR experiments + 2D spectra, COSY
Jan Novotný
novotnyjan@mail.muni.cz
March 21, 2018
1
H NMR spectrum of naringenine in d6-acetone
Basics of 1D FT spectroscopy
Draw FT representation of attached FID
records (reciever is located in the +y
direction):
Heteronuclear spin echo of 13
C-1
H3 group
By using vector diagrams determine the result of attached pulse sequence. First
realize what is the evolution of 13C signal resulting from offset? CPD=composite pulse
decoupling
2D NMR
Second dimension f1
� preparation period
=⇒ coherence
� evolution period
t1
FT
−→ f1
� increments
� evolution of
coherence
� mixing period
� transfer of
encoded
magnetisation
� measurable
signal
� detection of signal
t2
FT
−→ f2
acq
t1
prep
evolution
mixing
detection
t2
5t1
4t1
3t1
2t1
t1
2D NMR
2D spektrum
� FT in t1 - modulated 1D spectra
� FT in t2 - 2D spectrum
COSY
� easiest 2D
experiment
� correlates H nuclei
based on 2/3J
coupling
� through 2, 3, (4)
bonds
� antiphase
off-diagonal
crosspeak between
coupled atoms
� DQF-COSY modification
of basic
sequence, diagonal
crosspeaks in
absorption phase
acq
t1 t2
))
90 9090
P E M D
f1
f2
f1
f2
Hints for beginners
� Determination of individual spin systems - sharing
off-diagonal crosspeaks
� Isolated protons - only diagonal crosspeak
� Already known rules: symmetry, diastereotopicity, most
shielded/deshielded atoms etc.
COSY : β-cyclodextrine
5.0
5.0
4.5
4.5
4.0
4.0
3.5
3.5
δ2 - 1H (ppm)
5.0 5.0
4.5 4.5
4.0 4.0
3.5 3.5
δ1-1H(ppm)
Chinin - 1D 1
H
COSY - Chinin
10
10
8
8
6
6
4
4
2
2
δ2 - 1
H (ppm)
8 8
6 6
4 4
2 2
δ1-1H(ppm)
5
10
6
9
7
8
3
2
4
N
1
O
CH3
22
11
12
OH
17
16
N
13
15
14
18
19
20
21
COSY - Chinin10 8 6 4 2
8 8
6 6
4 4
2 2
δ1-1H(ppm)
5
10
6
9
7
8
3
2
4
N
1
O
CH3
22
11
12
OH
17
16
N
13
15
14
18
19
20
21
Next topic
1H-1H correlations (NOESY, ROESY, TOCSY)