NMR Spectral Assignment
HO-CH2-CH3
Cf) NMR Strcuture Determination (Elucidation):
determination of molecular structure without preconception
1H ppm
Simple 1D Analysis
Signal Intensities
Inegration
# of protons
Chemical shifts
Functional groups (Chemical environments)
J couplings
Splitting pattern and magnitude (Hz)
Bond connectivity
Signal Intensity
1H
2H1H
3H
1H ppm
Chemical Shifts
Proton
Carbon
J Couplings
Multiplet = 2nI +12JHH
3JHH
Karplus equation3J=Acos2 +Bcos +C
Dihedral angle ( )
Simple 1D AssignmentX reaction yielded styrene: 1H NMR (CDCl3, 100 MHz) δ:
7.35 (5H, m, phenyl), 6.7 (1H, dd, J = 8, 14 Hz, Ha), 5.75
(1H, d, J = 14 Hz, Hb), 5.25 (1H, d, 1H, J = 8 Hz, Hc).
a
b
c
Ha Hb Hc
o
o
m
mp
Ho HmHp
1D NOE (nuclear Overhauer effect)
Structure with 2 spin systems1
2 3
Simple 1D
with J couplings
1D with saturating the spin 3
1 2 3
NOE difference 1D
with saturating the spin 3
(1)
(2)
(3) = (2) – (1)
NMR Correlations and Structural Connectivity
Through-bond connectivity via scalar couplings (J) up to 3-bonds; COSY, TOCSY, HMQC, HMBC
Through-space connectivity via nuclear Overhauer effect (NOE) up to 5Å; NOESY, ROESY
C C
HH
3JHH coupling NOE
Structure vs. NMR Spin system
C C
HH
1J H
Cco
up
ling
H
2J H
Hco
up
ling
2D provides the correlation map between resonances.
C
H
C C C
HHH
Proton 1D
Carbon 1D
H ppm
H p
pm
H ppm
C p
pm
Proton decoupled
H ppm
C ppm
1 2 3 4
Proton Homonuclear 2D
COSY
TOCSY
NOESY
2,3JHH
≤ 5Å
2,3JHH
COrrelated SpectroscopY
Total COrrelated SpectroscopY
ROESY
Nuclear Overhauser Effect SpectroscopY
Rotating frame Overhauser Effect SpectroscopY
C-H Heteronuclear 2D
HMQC
HMBC
1JCH
2JCH3JCH
With suppressed 1JCH
HSQC
1JCH
Heteronuclear Multiple Quantum Coherence
Heteronuclear Single Quantum Coherence
Heteronuclear Multiple Bond Correlation
Proton Assignment Strategy
C C
H
H
1
2
3
1
2
3
D1
D2
D1
D2
Diagonal Peak
Cross Peak
1
2 3
COSY / TOCSY NOESY / ROESY
Trivial NOE Non-trivial NOE
Carbon Assignment Strategy
C C C
HH
C C C
HH
1
3
H ppm
C p
pm
1
(3,2)
3
H ppm
C p
pm
(1,2)
1 2 3 1 2 3
2,3JCH
1JCH
(1,3)
(3,1)
Proton Detection Pulse Sequences
HMQC HMBC
2-ethyl-1-indanone
Protons
(none)
(none)
H3
H4
H5
H6
(none)
H8
H9A, H9B
H10A,H10B
H11Me
Carbons
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
NMR sample; 2% (12.5mM) in CDCl3
Molecular Weight =160.21
Proton
H10AH10BH8H9AH9B
H11me
Proton Assignment
(none)
(none)
H3
H4
H5
H6
(none)
H8 (2.63)
H9A, H9B (2.83, 3.33)
H10A,H10B (1.55, 1.99)
H11Me (1.02)
Proton
solv
ent
H3H6 H5
H4H4
H5
Proton Assignment
(none)
(none)
H3 (7.47)
H4 (7.37?)
H5 (7.59?)
H6 (7.76)
(none)
H8 (2.63)
H9A, H9B (2.83, 3.33)
H10A,H10B (1.55, 1.99)
H11Me (1.02)
H3
H5
H4
H6
COSY
10B
10A
11
8
9B
9A
5
4
3
6
46
5
3
Ambiguous assignment
TOCSY
10B
10A
11
8
9B
9A
3
5
4
6
NOESY
9B
9A
3
3
5
4
6
NOE
Unambiguous COSY assignment
Carbon
Carbon Assignment
C1 (154.1?)
C2(137.2?)
C3 (124.1?)
C4 (126.8?)
C5 (127.5?)
C6 (134.9?)
C7 (209.2)
C8 (49.0)
C9 (32.6)
C10 (24.7)
C11 (11.9)
C1/2
C7
C11
C10C9
C8
C3/4/5/6
solv
ent
HMQC
Proton
Carb
on
11
10A 10B9A9B
8
6
5/4
4/5
3
C-H Correlations
(C,H) ppm
1 (154.1, none)
2 (137.2, none)
3 (126.8, 7.47)
4 (127.5, 7.37)
5 (134.9, 7.59)
6 (124.1, 7.76)
7 (209.2, none)
8 (49.0, 2.63)
9A (32.6, 2.83)
9B (32.6, 3.33)
10A (24.7, 1.55)
10B(24.7, 1.99)
11 (11.9, 1.02)
Corrected CH correlations
H ppm
H1(none)
H2(none)
H3 (7.47?)
H4(7.37?)
H5(7.59?)
H6(7.76?)
H7(none)
H8 (2.63)
H9AB (2.83, 3.33)
H10AB (1.55, 1.99)
H11Me (1.02)
C ppm
C1 (154.1?)
C2(137.2?)
C3 (124.1?)
C4 (126.8?)
C5 (127.5?)
C6 (134.9?)
C7 (209.2)
C8 (49.0)
C9 (32.6)
C10 (24.7)
C11 (11.9)
by HMQC
ambiguity
2
1
5
4
Tentative Assignment
HMBC
(9B, 8)
(9B, 2)
(9B, 7)
(5, 1)
(5, 3)
(4, 6)
(4, 2)
(C,H) ppm
1(137.2, none)
2 (154.1, none)
3 (126.8, 7.47)
5 (127.5, 7.37)
4 (134.9, 7.59)
6 (124.1, 7.76)
7 (209.2, none)
8 (49.0, 2.63)
9A (32.6, 2.83)
9B (32.6, 3.33)
10A (24.7, 1.55)
10B(24.7, 1.99)
11 (11.9, 1.02)
(3, 5)
(3, 1)
(6, 2)
(6, 4)
Mis
sin
g 8
Structure Elucidation Strategy using H–H and H–C correlation data Structure Elucidation Strategy
using C–C correlation data
Nat. Prod. Rep., 1999, 16, 241-248
Strategy for Structure Elucidation
Nat. Prod. Rep., 1999, 16, 241-248
ReferencesSDBS (Spectral Data Base System for Organic Compounds)
http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng
Database of NMR spectra
http://www.nmrdb.org
Organic Chemistry Resources Worldwide
http://www.organicworldwide.net/indexnew.html?nmr.html&boven.html&onder.html
C13-NMR predictions
http://csearch-nmr-data.blogspot.com/