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1st Semester 2017 and 2nd Semester 2018
Junior Sophister
Organic and Inorganic Practicals
Analytical Spectroscopy Course - NMR : Prof. Thorri Gunnlaugsson
NMR Facility : Dr John O’Brien, Dr Manuel Ruether
NMR analysis in Cocker lab : Lab Demonstrators
Revision from Senior Freshman Year
Organic Spectroscopy course : Prof. Isabel Rozzas
- NMR dealt with in lectures 2 to 5
- Topics included :
Hydrogen (Proton) NMR
Carbon 13 NMR
MRI - imaging using NMR
• NMR is the major analytical technique used to identify and characterise
materials today.
• NMR is used for :
– Identification of nuclides and their environment
– Conformational analysis
– Interactions of molecules
– Monitoring processes and reactions
• The main experimental methods are :
- FT NMR (superconducting magnets)
- Dynamic NMR, MRS, MRI
Introduction
Solution NMR
• Most common method by which NMR is carried out
• Materials and substances (liquids or solids) are dissolved in appropriate solvents
– deuterium replaces hydrogen in the solvent
• Many and varied experimental techniques in NMR, which are available to the user
• Usefulness is the fact that the nuclear spins under the influence of the magnetic field are
dependent on the molecular environment
• Position of peaks (resonances) are readily identifiable and information from peak
positions are reproducible from molecule to molecule
NMR of Liquids
• Applications :
– Academic (research, teaching)
– Industrial (chemical, pharmaceutical, medical, food, agriculture, ……)
In the fields of :
– Chemistry, Biochemistry, Biology, Physics, Pharmaceutical Chemistry, Medicine,
Genetics, Geology, Engineering, Forensic Science etc.
NMR Spectrometers
• Current equipment in TCD :
- 800 MHz (18.8 T) instrument for Biochemistry i.e. large protein work
- 600MHz (14.1T) solution instrument - Chemistry
- 400MHz (9.4T) solution instruments - Chemistry (2), TBSI (1)
• Major Nuclides
- 1H, 13C, 31P, 19F, 15N
- 2D, 11B, 17O, 29Si, 14N, 117Sn, ….
The 800MHz NMR
The Chemistry NMRs
600MHz NMR
400MHz NMRs
The biggest available NMR - 1000MHz
Yours for Millions of Euro !
Very sensitive
This NMR would need its own
warehouse in the middle of the
Cricket pitch because of the big
magnetic stray field
as of 2016 there is a new
generation of shielded magnets
at 1000Mhz
coming - 1200MHz NMR
A real NMR study
• Thyrotropin Releasing Hormone (TRH)
• TRH is a neuropeptide which is involved in some CNS disorders
• TRH has a function in the repair of brain and spinal disorders
Using NMR to identify a Hormone
A Case Study in NMR Methods
The TRH molecule is small peptide
• building block of a peptide is an amide linkage
C
O
N
H
C
H
C
CH2
O
N
H
TRH
• a Tripeptide with an amino terminated proline
• p-Glutamic acid Histidine Proline
N
C NH2
O
HN CH C
CH2
O
N
NH
C
O
NH
O
NMR of TRH
• The aim is to identify and assign all the positions of the atoms in the peptide
• Verify that the putative structure is correct
The tools
• Proton (Hydrogen) NMR
• Carbon-13 NMR
• Nitrogen-15 NMR
Proton (Hydrogen) NMR
• Position of the signal – resonance
• Hydrogen - hydrogen interaction
- spin coupling
• Ratio of the amount of proton signals
- integration
Carbon-13 NMR
• Carbon-13 is the active NMR nuclide
- only 1% of all Carbon
• Position of the Carbon signals
• Other Carbon-13 experiments to determine the
type and number of hydrogens attached or none
e.g. C, CH, CH2, CH3
Proton (HYDROGEN) NMR
( p p m )
1 . 02 . 03 . 04 . 05 . 06 . 07 . 08 . 09 . 01 0 . 01 1 . 01 2 . 0
Solvent
DMSO-d6
Water
NH or OH
Aromatic H , NH, OH Aliphatic CH, CH2, CH3s
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
1H NMR with peak labels and integration
(ratio of signal volume with respect to one another) 0
.9
76
6
1.
61
77
1.
00
00
1.
18
24
1.
55
20
0.
99
85
0.
81
73
1.
03
66
0.
82
07
6.
78
09
1.
93
72
8.
03
64
In
te
gr
al
11
.9
14
3
8.
18
14
7.
79
81
7.
53
09
7.
18
90
6.
97
01
6.
90
17
4.
63
54
4.
20
44
4.
06
20
3.
56
52
3.
32
37
2.
95
24
2.
81
06
2.
51
20
( p p m )
1 . 02 . 03 . 04 . 05 . 06 . 07 . 08 . 09 . 01 0 . 01 1 . 01 2 . 0
1.
61
77
1.
00
00
1.
18
24
1.
55
20
8.
18
14
7.
79
81
7.
53
09
7.
18
90
6.
97
01
6.
90
17
( p p m )
7 . 07 . 58 . 0
0.
99
85
0.
81
73
1.
03
66
4.
63
54
4.
20
44
4.
06
20
( p p m )
4 . 04 . 4
Integrals (value and trace)
Peak labels
solvent
3 x CHs
NH histidine
2x NH, 1x NH2
2x CH histidine
Carbon-13 NMR
( p p m )
2 03 04 05 06 07 08 09 01 0 01 1 01 2 01 3 01 4 01 5 01 6 01 7 01 8 0
Carbonyl –C=O
Aromatic C
Aliphatic CH s CH2 s
SOLVENT N
C NH2
O
HN CH C
CH2
O
N
NH
C
O
NH
O
More Types of Carbon-13 NMR
Carbon DEPT (distortionless enhancement by polarisation transfer)
3 04 05 06 07 08 09 01 0 01 1 01 2 01 3 01 4 01 5 01 6 01 7 0
3 04 05 06 07 08 09 01 0 01 1 01 2 01 3 01 4 01 5 01 6 01 7 0
( p p m )
CH2s
CHs
CHs
C -C=Os
Carbon DEPT 135°
13C Carbonyl (C=O) and methine (CH) signals
( p p m )
2 03 04 05 06 07 08 09 01 0 01 1 01 2 01 3 01 4 01 5 01 6 01 7 01 8 0
( p p m )
1 7 01 7 21 7 41 7 61 7 8
( p p m )
5 05 25 45 65 86 0
CH
N
C NH2
O
HN CH C
CH2
O
N
NH
C
O
CH
CNH
O
4 x C=O
CH
CH CH
Note the extra signals from an isomer *
and a rotormer
*
More NMR tools - 2D
• CH and NH correlation – through bonds
- direct (one) bond or further out
• HH correlation - through bonds, looks more complex
- connections are the off diagonal signals
• Through space connections for HH - NOe, NOESY
• Selective 1D versions of the 2D experiments
13C-1H Correlation (edited HSQC)
Links carbon signals to hydrogen(s)
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
C
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
13C axis
1H axis
15N-1H Correlation (15N HSQC)
NH
NH
NH
NH2
N
C NH2
O
HN CH C
CH2
O
N
NH
C
O
NH
O
15N axis
1H axis
NH2
NH NH
CH
CH
Combining NH and CH 2D Correlation Experiments
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
C
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
Peak overlap
Problems in 1H spectra
0.
99
85
0.
81
73
1.
03
66
0.
82
07
6.
78
09
1.
93
72
8.
03
64
In
te
gr
al
4.
63
54
4.
20
44
4.
06
20
3.
56
52
3.
32
37
2.
95
24
2.
81
06
2.
51
20
( p p m )
1 . 41 . 61 . 82 . 02 . 22 . 42 . 62 . 83 . 03 . 23 . 43 . 63 . 84 . 04 . 24 . 44 . 64 . 8
Peak overlap
4 x CH2s
Complex spin- spin coupling
CH2 CH2
3 X CHs
CH correlation in aliphatic region
3x CH
CH2
CH2
Two separate proton signals
for one carbon 46.7
3.56, 3.20
30.3
2.95, 2.80
Identifying the remaining methylene peaks
Possible to identify the proton
peaks directly for the 4
overlaping CH2s
13C axis
1H axis
2.01, 1.86 2.11, 2.06
1.83, 1.78
2.95, 2.80
2.22, 1.85
25.0
24.2
29.0
29.2
30.3
Gathering the Information in a Peak table with assignments for carbon and nitrogen attached to protons
d
13C
ppm
d 15N
ppm
d 1H
ppm
CH aromatic
134.9
-
6.97
CH
113.7
-
7.53
CH aliphatic
60.1
-
4.21
CH
55.2
-
4.05
CH aliphatic
51.2
4.63
CH2
46.7
-
3.56, 3.20
CH2
30.3
-
2.95, 2.80
CH2
29.2
-
2.01, 1.86
CH2
29.0
-
2.11, 2.06
CH2
25.0
-
2.22, 1.85
CH2
24.2
-
1.83, 1.78
NH
-
166.6
11.92
NH
-
122.2
8.21
NH
-
121.1
7.80
NH2
-
105.2
8.18, 6.90
HH correlation - links local protons
HNHC
CH2
NH
histidine aliphatic fragment
CH CH2
H2C
CNH
CH
H2C
C
O
NH
O
CH
CH2
N
NH
C
O
N
CHCH2
CH2
H2C
CH2
C NH2
O
HH Correlation - Links to local protons (diagonal is the 1D spectrum)
CH
HH COSY
Combined through bond (HH) and space (NOE) correlation
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
C
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
CHhis CH2 pglu
NHhis CHpglu
HH COSY and NOESY
Selective through bond and through space NMR
experiments
• These are 1D analogues of 2D NMR experiments
• They are very powerful tools for elucidation when appropriate
• There are two classes of experiments
– through bond - selective TOCSY or COSY
– through space - selective NOE or ROE
• Normally quicker to run than their 2D equivalent
• Extract specific and often detailed information
• Requirement that individual signals are accessible
Selective HH correlation experiments - through bond connections
same information as 2D TOCSY experiments but with better resolution
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
C
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
correlated spins from the separate CHs peaks
(found in 4-5ppm region)
Histidine -NH-CH-CH2-
Proline - no NH
-CH-CH2-CH2-CH2-
p-glu -NH-CH-CH2-CH2-
4.06 ppm
4.21 ppm
4.63 ppm
Selective Nuclear Overhauser ( Noe) experiments
- through space connections
*CH
*CH
*CH
* Irradiated CH peak
proline
p-glu
histidine
NH2 8.18
NH 8.19
CH 6.97
NHs 7.80, 8.19
CH2
CH2CH
N
H2C
C NH2
O
HN CH C
CH2
O
C
N
HC NH
CH
C
O
CH
H2C
H2C
CNH
O
Long range CH correlation (HMBC) Very useful - links proton to carbon with NO proton(s) attached
Carbonyl peaks
-C=O
13C axis
1H axis
177.4
173.7
171.9
170.0
p-glu
His CH - two –C=O links
NH CH
H2C
CNH
CH
H2C
C
O
NH
O
CH
CH2
N
NH
C
O
N
CHCH2
CH2
H2C
CH2
C NH2
O
Long range CH correlation (HMBC)
-C=O to CH links -NH2 to -C=O
p-glu
pro
his
CH
N
C NH2
O
HN CH C
CH2
O
N
HC NH
CH
C
O
CH
CNH
O
173.7 to 6.90 and 8.18 ppm 4.63 to 170.0 and 171.9 ppm
4.21 to 173.7 ppm 177.4 to 4.06 ppm
177.4
170.0
171.9
173.4
4.63 4.21 4.06
Proton NMR assignments
N
C
H2N
O
NH
CH
C
CH2
O
NNHHN
C
O
O
7.53
6.97
6.90,8.18
4.63
4.21
4.06
3.56, 3.20
2.95, 2.80
11.92
8.197.80
2.22, 1.85
2.11, 2.06
2.01, 1.86
1.83, 1.78
Carbon-13 , Nitrogen-15 NMR assignments
N
C
H2N
O
NH
CH
C
CH2
O
NNHHN
C
O
O
177.4
173.7
171.9
170.0
135.9134.9
113.7
30.351.2
55.2
60.1
29.2
29.0
25.0
24.2
46.7
105.2
121.1
122.2
166.6
15N assignments 13C assignments