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NMR N uclear M agnetic R esonance. Heteronuclear NMR:. Index. NMR-basics. H-NMR. NMR-Symmetry. Heteronuclear-NMR. Proton with Carbon-13 coupling. Proton with Fluorine-19 coupling. Fluorine-19: Fluoroacetone. Phosphorus-31. Phosphorus-31: Coupling with 1 H.

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nmr n uclear m agnetic r esonance

NMRNuclear Magnetic Resonance

HeteronuclearNMR:

Index

NMR-basics

H-NMR

NMR-Symmetry

Heteronuclear-NMR

phosphorus 319

AQ: P31

AQ: P31

Phosphorus-31

28 Hz

8Hz

dt

H1 decoupling

phosphorus 3110

AQ: P31

39 Hz

Phosphorus-31

9 Hz

H1 decoupling

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

n15 nmr
N15 NMR

10 mm tube

25% in CDCl3

Inverse gated D1=15 s

Total time 12 hrs

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

c 13 nmr quantitative
C-13 NMR: Quantitative??
  • In C-13, some carbons can have long relaxation time: If the relaxation delay is not long enough, the long relaxation carbons will not achieve full amplitude
  • NOEs varies for the various carbons
  • Number of data points used to record the data might not be sufficient
  • The efficiency of the pulse vary depending if a signal is in the center of the window or on the side.
normal c13 measure time 1 5 hrs noe present no integration possible

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

AQ: C13

Normal C13 measure time 1.5 hrsNOE present, no integration possible

2

C2

3

1

H1 decoupling

3JCP = 2.3

3JCP = 5.5

2JCP = 7.2

1JCP = 201.3

C3

PCHO2

C1

1JCP

OCH2

CH3

c13 nmr

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

AQ: C13

AQ: C13

C13-NMR

2

d

1

3

C13, H-coupled

H1 decoupling

dd

t

q

C2

PCHO2

C3

1JCP

C1

OCH2

CH3

c13 coupling to proton

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

C13 coupling to proton

2

1

3

3JC3-H2 = 7.9

2JC3-H2’ = 5.4

C3-Cl

c13 extracting j values

AQ: C13

AQ: C13

AQ: C13

C13 extracting J values

Me

3JPC = 5.5 Hz

H1 decoupling

CH2selective dec.

Quartet : CH3

split by P (doublet)

Split by CH2 triplet

1JCH = 127.7 Hz

c13 inverse gated integration measuring time 28 hours d1 120 s

NMR – From Spectra to Structures An Experimental approachSecond edition (2007) Springler-Verlag

Terence N. Mitchellm Burkhard Costisella

AQ: C13

C13 inverse gated: integrationMeasuring time: 28 hoursD1=120 s

H1 decoupling

D1

off

multiplicity detection
Multiplicity detection

DEPT : CH, CH3

CH2

APT : CH, CH3

C , CH2

Normal C13

carbon 13 shift26
Carbon-13 Shift

Acid

Amide

Ester

Ketone

Aldehyde

O

C = O

C – O

C – O

= C =

C  C

C – C

C=C

200

150

100

50

0

alkanes
Alkanes

d = -2.5 + SnA

1 2 3 4 5

CH3-CH2-CH-CH2-CH3

6

CH3

dC1 = -2.5 + 1a + 1b + 2g + 1d

dC1 = -2.5 + 9.1 + 9.4 + 2(-2.5) + .3 = 11.3

dC2 = -2.5 + 2a + 2b + 1g + 2o(3o)

(Secondary carbon bound to tertiary)

dC2 = -2.5 + 18.2 + 18.8 + (-2.5) + (-2.5) = 29.5

dC3 = -2.5 + 3a + 2b + 2{3o(2o)}

dC3 = -2.5 + 27.3 + 18.8 + (-7.4) = 36.2

dC6 = -2.5 + 1a + 2b + 2g + 1o(3o) = 19.3

alkanes28
Alkanes

dC1 = -2.5 + 1a + 1b + 2g + 1d = 11.3

dC2 = -2.5 + 2a + 2b + 1g + 2o(3o) = 29.5

dC3 = -2.5 + 3a + 2b + 2{3o(2o)} = 36.2

dC6 = -2.5 + 1a + 2b + 2g + 1o(3o) = 19.3

C2

C1

C3

C6

2

3

1

6

substituted alkanes
Substituted Alkanes

CH3-CH2-CH2-CH2-CH3

13.9 – 22.8 – 34.7

g b a

CH3-CH2-CH-CH2-CH3

OH

CH = 34.7 + 41 = 75.7 ppm

CH2 = 22.8 + 8 = 30.0 ppm

CH3 = 13.9 + (-5) = 8.9 ppm

slide30

CH = 34.7 + 41 = 75.7 ppm

g b a

CH3-CH2-CH-CH2-CH3

CH2 = 22.8 + 8 = 30.0 ppm

OH

CH3 = 13.9 + (-5) = 8.9 ppm

shift calculation
Shift Calculation:
  • Select a suitable model
  • Use proper substituent effects to predict the shifts of the various carbonsThis gives a crude estimate without taking into account the geometry
  • For cyclohexanes, substituents effects are compiled in terms of axial/equatorial orientation
unsaturated compounds electronic effects

d-

d+

CH2

CH

OMe

CH2

CH

OMe

84.2

153.2

CH2

CH2

C

C

C

d-

d+

OEt

CH

C

CH

OEt

C

Unsaturated compounds: Electronic Effects

Alkenes

d-

129.3

d+

157

Allenes

75-97

200-215

Alkynes

65-90 ppm

23.2

89.4

example benzene calculation distinguish isomers39
Example: Benzene Calculation => distinguish isomers

Experimental shifts

152.5, 136.6, 131.7, 126.3, 121.9, 116.3

Subst. C1 ortho meta para

Me 9.2 0.7 -0.1 -3.0

CH(Me)2 20.2 -2.2 -0.3 -2.8

OH 26.9 -12.8 1.4 -7.4

C1 = 128 + 9.2 – 2.8 +1.4 = 135.8

C2 = 128 + .7 - 0.3 –7.4 = 121.0

C3 = 128 – 0.1 – 2.2 + 1.4 = 127.1

C4 = 128 – 3.0 + 20.2 – 12.8 = 132.4

C5 = 128 – 0.1 – 2.2 + 26.9 = 152.6

C6 = 128 + 0.7 – 0.3 – 12.8 = 115.6

C1 = 128 + 9.2 – 2.8 – 12.8 = 121.6

C2 = 128 + .7 - 0.3 + 1.4 = 129.8

C3 = 128 – 0.1 – 2.2 - 7.4 = 118.3

C4 = 128 – 3.0 + 20.2 + 1.4 = 146.6

C5 = 128 – 0.1 – 2.2 - 12.8 = 112.9

C6 = 128 + 0.7 – 0.3 + 26.9 = 155.3

slide40

C1 = 128 + 9.2 – 2.8 +1.4 = 135.8

C2 = 128 + .7 - 0.3 –7.4 = 121.0

C3 = 128 – 0.1 – 2.2 + 1.4 = 127.1

C4 = 128 – 3.0 + 20.2 – 12.8 = 132.4

C5 = 128 – 0.1 – 2.2 + 26.9 = 152.6

C6 = 128 + 0.7 – 0.3 – 12.8 = 115.6

C2

C6

C3

C5

C1

C4

slide41

C1 = 128 + 9.2 – 2.8 – 12.8 = 121.6

C2 = 128 + .7 - 0.3 + 1.4 = 129.8

C3 = 128 – 0.1 – 2.2 - 7.4 = 118.3

C4 = 128 – 3.0 + 20.2 + 1.4 = 146.6

C5 = 128 – 0.1 – 2.2 - 12.8 = 112.9

C6 = 128 + 0.7 – 0.3 + 26.9 = 155.3

C3

C2

C5

C6

C4

C1

carbonyls c o
CarbonylsC=O

Acid

Ester

coupling between 1 h and 13 c 1 j ch
Coupling between 1H and 13C1JCH

One bond coupling is proportional to % s charactersp3 : ~125 Hzsp2: ~ 165 Hzsp : ~ 250 Hz

Electronegative subst. Increase JCH-OR => J ~ 140 HzCH-Cl => J ~ 150 Hz

coupling between 1 h and 13 c sp 3 1 j ch
Coupling between 1H and 13C sp3: 1JCH

Increase of coupling values with the electronegativity of the substituant : CHZ

Z : Li1JCH = 98 Hz

Z : C1JCH = 125-129 Hz

Z : NR1JCH = 131-134 Hz

Z : S1JCH = 138 Hz

Z : OR1JCH = 140 Hz

Z : Cl1JCH = 150 Hz

Z : (OR)21JCH = 162 Hz

Z : Cl2 1JCH = 178 Hz

1JCH = 161 Hz

1JCH = 180 Hz

1JCH = 134 Hz

1JCH = 137 Hz

1JCH = 150 Hz

coupling between 1 h and 13 c sp 2 1 j ch
Coupling between 1H and 13C sp2: 1JCH

Increase of coupling values with the electronegativity of the substituant : =CHZ

=C-H 1JCH = 157 Hz

1JCH = 238 Hz

1JCH = 172 Hz

1JCH = 250 Hz

1JCH = ~200 Hz

1JCH = 182 Hz

1JCH = 202 Hz

use of 1 j ch
Use of 1JCH

Extremely useful for molecules where 1JCHlarger than usual

Diagnostic for alkynes (250 Hz) , epoxides (180 Hz) , hemiacetal (162 Hz) and cyclopropane (161 Hz)

coupling between 13 c and 13 c 1 j cc
Coupling between 13C and 13C : 1JCC

Measurable only on enriched compound

Useful for setting up pulse sequences like INADEQUATE

sp3

R-CH2-CH31JCC = 35 Hz

1JCC = 48 Hz

sp2

1JCC = 44 Hz

1JCC = 56 Hz

1JCC = 54 Hz

1JCC = 74 Hz

1JCC = 74 Hz

1JCC = 123 Hz

coupling between 1 h and 13 c 2 j ch
Coupling between 1H and 13C2JCH

Usually small and difficult to predict

Typical values: -8 to +4 Hz

coupling between 1 h and 13 c 3 j ch
Coupling between 1H and 13C3JCH

Depend on dihedral angle between coupled nuclei: Karplus curve

0 angle : 3JC-H ~ 3-7 Hz

90 angle : 3JC-H ~ 0 Hz

180 angle: 3JC-H ~ 7-12 Hz

This behavior (Jcis < Jtrans) is useful specially in sp2 carbons to help distinguishing isomers

3 j example of usage
3J : example of usage

Decouple

OMe

CO

CN (J=13.7 Hz)

c 13 coupling with other nuclei than h
C-13 Coupling with other nuclei than H

1JCD = 20 Hz

1JCF = -160 Hz

1JCN = 6-8 Hz

1JP-H = >600 Hz

29 si h nmr

29Si

29Si : H– NMR

3JSiH-CH2 = 3.1 Hz

Si-H: Septet

29 si h nmr59

29Si

29Si : H– NMR

d 1JSi-H

quintet 2JCH2-Si

d 3JHSi-Si

Si-H : Quintet

CH2

A B

19 f nmr
19F – NMR

Index

NMR-basics

H-NMR

NMR-Symmetry

Heteronuclear-NMR

Dynamic-NMR