C8953
NMR structural analysis - seminar
2D NMR spectra, COSY+TOCSY Kateřina Peterková
423 977@mail.muni.cz
March 31, 2021
Determination Of regioiSOmerS - note number of signals, splitting and 5
2D NMR
Second dimension ^
► preparation period => coherence
► evolution period
U —> U
► increments
► evolution of coherence
► mixing period
► transfer of encoded magnetisation
► measurable signal
► detection of signal
t2 —> h
ti
t2
prep
evolution
mixing
2D NMR
2D spektrum
► FT in ti - modulated 1D spectra
► FT in t2 - 2D spectrum
COSY
► easiest 2D experiment
► correlates H nuclei based on 2/3 J coupling
► through 2, 3, (4) bonds
► antiphase off-diagonal crosspeak between coupled atoms
► DQF-COSY-modification of basic sequence, diagonal crosspeaks in absorption phase
90 90 90
l/2[cos(fi*i + irJh) - cos(fiii - TrJti)] l/2[sin(fiii + vrJii) + sin(0<i - vrJti)]
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 : ß-cyclodextrine
6^0H
H OH
J7
3.5
4.0'
£
Q. Q.
to
4.5'
5.0
5.0
5.0
4.5
4.5
4.0
3.5
4
4.0
3.5
ô2 - 1H (ppm)
3.5
4.0
4.5
5.0
COSY - Chinin
COSY - Chinin
10 8
6
2\
4H
Q_ Q.
CO
6H
8H
1 1 1
1 1 1
I I I I I I
1 1
b e
o o
&4
tt 9
o a
< □ ► <g > < 1 ►    l   -O o, Or
TOCSY (TOtal Correlation Spectroscopy)
spin lock - isotropic mixing
► series of short 180° pulses
► "lock-in" of spins in transversal plane
► higher power in case of TOCSY, offset set into the middle (on resonance)
► smaller power in case of ROESY, offset set into the edge (off resonance)
► crosstalk (ROE transfer in TOCSY, J-coupling in ROESY)
P   E M
6
_l_
4
-Mr.
It f • m
6
1H (ppm)
NAD+: TOCSY (40ms), detail of aromatics
9.0 8.5 82 - 1H (ppm)
NAD+: TOCSY (40ms), detail of aliphatics
6.5
4.5
E 5.0
Cl
CL
KD
5.5
6.0
6.5
6.0
6.0
5.5
5.0
5.5 5.0 Ď2 - 1H (ppm)
4.5
4.0
Z*
00
8'
o
0-Nic
6
4
5
N1
ľ
h4.5
*NH2
8
h5.0
3] |2" OH OH
10
NH2
Ade =P-0
L O
^5' 4'
ľ     c    16
h5.5
ľ
3'| |2" OH OH
0
0 s
h6.0
4.5
4.0
Next topic
1H-1 H trough space correlations (NOESY, ROESY)