Post on 05-Jan-2016
description
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
0 ppm10 ppm
DownfieldDeshielded
UpfieldShielded
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)
H3H2 H4
H3
H2
H4
3
2
4
H6
H8
H7
H3H2 H4
H3
H2
H4
3
2
4
H7H8H6
7
6
8
H6
H8
H7
H3H2 H4
H3
H2
H4
3
2
4
H7H8H6
7
6
8
H1
H1
1
H5
5
H6
H8
H7
H3H2 H4
H3
H2
H4
3
2
4
H7H8H6
7
6
8
H1
H1
1H5
H10
H11
H9
H10H11 H9
H6
H8
H7
H3
H2
H4
H1
H5
H5
H3H2 H4 H7
H8H6H1
5
3
2
47
6
8
111
10
9
H10H11 H9H5
H3H2 H4 H7
H8H6H1
H10
H11
H9 H
6H
8H
7H
3H
2H
4H
1H
5
5
3
2
47
6
8
111
10
9
LONG-RANGE COUPLINGH10
H11 H9H5
H3H2 H4 H7
H8H6H1
H10
H11
H9 H
6H
8H
7H
3H
2H
4H
1H
5
5
3
2
47
6
8
111
10
9
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
H10H11 H9H5
H3H2 H4 H7
H8H6H1
5
3
2
4
7
6
8
1
11
10
9
H10H11 H9H5
H3H2 H4 H7
H8H6H1
5
3
2
4
7
6
8
1
11
10
9
# of total peaks: 1 3 1 4 25
# of non-H C peaks: 1 1 0 1 02
C1
C5C10
C3
C7
C11
C2
C6
C4
C8C9
C12
C13
??????????C12, C13, C14, C15, C17
??????????C14, C15, C17
Thank YouAny Questions?