Tutorial on 2D-NMR Using COSY & HSQC to Assist in Assigning

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Tutorial on 2D-NMR:
Using COSY & HSQC to Assist in
Assigning 1H & 13C NMR Spectra
1H
NMR
• Chemical shift (δ) depends on molecular structure
and solvent
• 1H nuclei sensitive to hybridization of atom to
which H is attached and electronic effects
– EDG’s shield nuclei  shift upfield  lower δ
– EWG’s deshield nuclei  shift downfield  higher δ
Downfield
Deshielded
Upfield
Shielded
10 ppm
0 ppm
1H
NMR
• Spin-spin coupling effects: interaction between
nuclei through bonds
– Causes splitting in observed peak (s, d, dd, t, m…)
– Coupling constants: magnitude of splitting (Hz)
• Hz (not ppm) since effect is independent of applied mag. fld.
• Caused by mag. fld. of another nuclei
2-D NMR
• Determine structure (especially for molecules
too complicated for 1-D NMR)
• Involves series of 1-D NMR experiments
• Doesn’t need to use the complicated coupling
constants
Correlation Spectroscopy (COSY)
• Homonuclear: plots 1H NMR on both x and y-axis
• Diagonal divides the spectrum into 2 equal halves
• Cross-signals: symmetrical to diagonal; contain the
relevant info
• FAB-FOUR
– 1H NMR (~5 min)
– COSY (~30 min)
– 13C NMR (depends…)
– HSQC (~30 min)
3
4
2
H4
H3
H3
H2
3
H4
7
4
H2
8
2
6
H8
H4
H7
H3
H6 H2
H3
H4 H7
3
7
H8
4
H6 H2
8
2
6
1
H6 H2
H8
H4
H7
H3
H1
H3
H4 H7
3
7
H8
4
H6 H2
8
2
H1
6
5
1
H5 H1
H8
H4
H7
H3
H6 H2
H4 H7
3
7
H8
4
8
H6 H2
H5H1
H3
2
9
11
5
1
6
10
H11
H9
H6 H2
H
H8 10
H4
H7
H3
H5 H1
H4 H7
3
7
H8
H10
4
H9
H6 H2
8
2
9
H11
H5H1
H3
11
5
1
6
10
H11
H9
H6 H2
H
H8 10
H4
H7
H3
H5 H1
LONG-RANGE COUPLING
H4 H7
3
7
H8
H10
4
H9
H6 H2
8
2
9
H11
H5H1
H3
11
5
1
6
10
Heteronuclear Single Quantum
Coherence (HSQC)
• Plots 1H NMR on x-axis and 13C NMR on y-axis
• Utilizes 1 bond coupling between H and C
• Eliminating all the H containing C’s eliminates
many C’s assignments
– Leaves only on-H containing C’s to assign
HSQC Spectrum
H5 H1
H11
H9
H6 H2
H
H8 10
H4
H7
H3
51
10
7
11
6
9
2
8
4
3
H5 H1
H11
H9
H6 H2
H
H8 10
H4
H7
H3
51
10
7
11
6
9
2
8
4
3
# of total peaks:
5
1
3
1
4
2
# of non-H C peaks:
2
1
1
0
1
0
??????????
C12, C13
C15
14,, C
14,, C17
15, C17
C9 C8
C4
C13
C12
C6
C2
C11
C7
C1
C3
C10 C5
Thank You
Any Questions?

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