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/