R
Showcasing benchtop NMR of small organic molecules
Example: Ibuprofen
Ibuprofen
H3C
Example of benchtop
NMR on small organic molecules
H3C
CH3 Ibuprofen (C13H18O2) is a non-steroidal antiShowcasing
benchtop NMR
small organic
molecules
inflammatory
drugof
(NSAID)
and is used
commonly
Ibuprofen (C13H18O2) is a non-steroidal antiinflammatory
drug (NSAID)
and
is commonly
for pain
Example:
Ibuprofen
used
for
pain
relief,
fever
reduction
and
against
relief, fever reduction and against inflammation.
inflammation.
H3C
O
H3C
OH
CH3
O
1H
OHNMR
Ibuprofen (C13H18O2) is a non-steroidal antiinflammatory drug (NSAID) and is commonly
used for pain relief, fever reduction and against
inflammation.
spectrum
1H NMR
in Figure
1. The spectrum was recorded
The 1H NMR spectrum of 200 mM ibuprofen in CDCl3 is shown
spectrum
1H NMR spectrum of 200 mM ibuprofen in CDCl
The
is
shown
in Figure
1. The and
spectrum
1
1
well resolved,
can
in a single scan, taking 7 seconds to acquire. All peaks and H- H3couplings are
1H NMR spectrum of 200 mM ibuprofen in CDCl is shown in1Figure
1
The
1.
The
spectrum
couplings
was recorded
in a single
scan, taking 7 seconds to acquire. All peaks
and H- H
3
be assigned
to the molecular
structure.
1
1
was recorded in a single scan, taking 7 seconds to acquire. All peaks and H- H couplings
are well resolved, and can beareassigned
toand
thecanmolecular
well resolved,
be assigned tostructure.
the molecular structure.
Figure 1: Proton NMR spectrum of 200 mM ibuprofen in CDCl3.
Figure 1: Proton NMR spectrum of 200 mM ibuprofen in CDCl3.
Figure 1: Proton NMR spectrum of 200 mM ibuprofen in CDCl3.
1H NMR RELAXATION
1
1H
NMR relaxation
The relaxation
time measurements are shown in Figures 2 - 4. Note the long T
H NMR
relaxation
1 and short T2
value of the exchanging hydroxyl proton. The amplitude of the first data point scales with
the number of protons for the corresponding peak.
The relaxation time measurements are shown in Figures 2 - 4. Note the long T1 and short T2
0.9 s The amplitude of the first data point
0.9 scales
s
The relaxation time
valuemeasurements
of the exchangingare
hydroxyl proton.
with
0.9 s
0.9 s
1
the
number
of
protons
for
the
corresponding
peak.
H NMR relaxation 1.3 s
shown in Figures 2 - 4. Note the long
1.3 s
2.5 s
2.3 s
1.4 s
1.3 s 2.1 s
1.3 s
T1 and short T2 value
1.3 s
0.9 s of the exchanging
0.9 s 1.3 s
The relaxation
timeof
measurements
are shown
T and short T2
3.5 sin Figures 2 - 4. Note the long
hydroxyl proton. The
amplitude
the0.9 s
0.9 1s 0.13 s
value of the exchanging hydroxyl proton. The amplitude of the first data point scales with
first data point scales
withofthe
number
1.3 s peak. 1.4 s
1.3 s
2.5
s for the corresponding
2.3 s
the2.1
number
protons
s
Figure
2: Proton
T1 (left)
and T
T2
relaxation
time
each proton
position
of the molecule
and
(right)
relaxation
for each
proton
Proton
T1 (left)
2 (right)
of protons for the corresponding peak.1.3 s1.3
1.3forstime
s
1.3 s
1.3 s
0.9 s
3.5 s
0.9 s
position of the0.9molecule
s 0.13 s
0.9 s
1.3 s
1.3 s
2.5 s
2.3 s
2.1 s
1.4 s
relaxation time for each proton position1.3
of the
Figure 2: Proton T1 (left) and T1.3
s
s molecule
2 (right)
3.5 s
0.13 s
Figure 2: Proton T1 (left) and T2 (right) relaxation time for each proton position of the molecule
Figure 3: Proton T1 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 3: Proton T1 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 2: Proton T1 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 3: Proton T1 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 4: Proton T2 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 4: Proton T2 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 4: Proton T2 relaxation time measurement of 200 mM ibuprofen in CDCl3.
Figure 3: Proton T2 relaxation time measurement of 200 mM ibuprofen in CDCl3.
1.3 s
2D COSY
2D COSY
The 2D COSY spectrum is shown in Figure 4. It clearly shows two spin systems (2,13) and
(9,10,11,12). For example, the methyl group at position 13 only couples to the CH group at
position 2, whilst the methyl groups at positions 11 and 12 couple to CH and CH2 groups at
positions 10 and 9. There is no coupling of positions (9,10,11,12) to either 2 or 13.
2D COSY
The 2D COSY
spectrum
is shown
The 2D COSY spectrum
is shown
in Figure
4.in Figure 4. It clearly shows two spin systems (2,13) and
(9,10,11,12).
For
example,
the
methyl
group at position 13 only couples to the CH group at
It clearly shows two spin systems (2,13) and
position 2, whilst the methyl groups at positions 11 and 12 couple to CH and CH2 groups at
(9,10,11,12). For example, the methyl group at
positions 10 and 9. There is no coupling of positions (9,10,11,12) to either 2 or 13.
position 13 only couples to the CH group at
position 2, whilst the methyl groups at positions
11 and 12 couple to CH and CH2 groups at
positions 10 and 9. There is no coupling of
positions (9,10,11,12) to either 2 or 13.
Figure 4: COSY spectrum of 200 mM ibuprofen in CDCl3. The cross-peaks and
corresponding exchanging protons are marked by colour-coded ellipses and arrows.
Figure 4: COSY spectrum of 200 mM ibuprofen in CDCl3. The cross-peaks and
corresponding exchanging protons are marked by colour-coded ellipses and arrows.
Figure 4: COSY spectrum of 200 mM ibuprofen in CDCl3. The cross-peaks and corresponding
exchanging protons are marked by colour-coded ellipses and arrows.
2D HOMONUCLEAR J-RESOLVED SPECTROSCOPY
homonuclear
spectroscopy
spectrum.
Vertical traces through the peaks in the
In the 2D homonuclear2D
j-resolved
spectrum the j-resolved
2D spectrum yield the peak multiplicities, as shown
chemical shift is along the direct (f2) direction
In the 2D homonuclear j-resolved spectrum the chemical shift is along the direct (f2)
by the green lines in Figure 5, and enables
and the effects of proton-proton coupling along
direction and the effects of proton-proton coupling along the indirect (f1) dimension. This
the measurement of proton-proton coupling
the indirect (f1) dimension. This allows the full
allows the full assignment of chemical shifts of overlapping multiplets, and can allow
frequencies. By comparing the coupling
assignment of chemical shifts of overlapping
otherwise unresolved couplings to be measured. The projection along the f1 dimension
frequencies between different peaks, it is possible
multiplets, and can allow otherwise unresolved
yields a “decoupled” 1D proton spectrum. Figure 5 shows the 2D homonuclear j-resolved
to extract information about which peaks are
couplings to be measured. The projection along
spectrum of ibuprofen, along with the 1D proton spectrum as blue line. The vertical
coupled to each other. For example, both the
the f1 dimension
yields
a
“decoupled”
1D
proton
projection shows how the multiplets collapse into a single peak, which greatly simplifies
multiplet at 1.90 ppm and the doublet at 3.78 ppm
spectrum.the
Figure
5 shows the 2D homonuclear
1D spectrum.
haveyield
a splitting
ofmultiplicities,
6.5 Hz, suggesting
that these
j-resolvedVertical
spectrum
of
ibuprofen,
along
with
the
traces through the peaks in the 2D spectrum
the peak
as shown
groups are of
coupled
to eachcoupling
other. These couplings
1D protonby
spectrum
blue
The
the greenas
lines
in line.
Figure
5, vertical
and enables the measurement
proton-proton
confirm
the
findings
of
the
COSY
experiment in
projectionfrequencies.
shows howBy
thecomparing
multipletsthe
collapse
coupling frequencies between different peaks, it is possible
Figure
into a single
peak, which
greatly
simplifies
the 1Dare coupled
to extract
information
about
which peaks
to 4.
each other. For example, both the
6.5 Hz
6.5 Hz
multiplet at 1.90 ppm and the doublet at 3.78 ppm have a splitting of 6.5 Hz, suggesting
that these groups are coupled to each other. These couplings confirm the findings of the
COSY experiment in Figure 4.
Figure 5: Homonuclear j-resolved spectrum of 200 mM ibuprofen in CDCl3. The multiplet
splitting
frequencies for
differentspectrum
couplingsofare
asininCDCl
Figure
4. multiplet splitting
Figure
5: Homonuclear
j-resolved
200colour-coded
mM ibuprofen
3. The
frequencies for different couplings are colour-coded as in Figure 4.
2D homonuclear j-resolved spectroscopy
2D homonuclear
j-resolved spectroscopy
One unusual and often neglected
feature of this experiment is that second order coupl
2D HOMONUCLEAR
J-RESOLVED
SPECTROSCOPY
effects show up in the indirect (f1) direction as extra peaks equidistant from the coup
partners
wellexperiment
removed from
the zero
frequency
the indirect dimension. These peaks
One unusual and often neglected feature
of this
is that
second
order in
coupling
often neglected as artefacts, but provide direct evidence of second order coupling part
effects show up in the indirect (f1) direction as extra peaks equidistant from the coupling
These extra peaks and coupling partners are marked by colour-coded ellipses and arro
One unusual partners
and often
neglected
feature
this
thisdimension.
spectrumThese
is based
the same data
well
removed from
the of
zero
frequency Note
in the that
indirect
peaksonare
Figure 6. Note that this spectrum is based on the same data as Figure 5, only the scalin
as artefacts,
but provide
direct
evidence
of
second
order
coupling
partners.
experiment isoften
that neglected
second order
coupling
effects
as
Figure
5,
only
the
scaling
has
changed.
changed.
These
extra(f1)
peaks
and coupling
partners are marked by colour-coded ellipses and arrows in
show up in the
indirect
direction
as extra
Figurefrom
6. Note
this spectrum
is based
peaks equidistant
thethat
coupling
partners
well on the same data as Figure 5, only the scaling has
changed.
removed from the zero frequency in the indirect
dimension. These peaks are often neglected as
artefacts, but provide direct evidence of second
order coupling partners. These extra peaks and
coupling partners are marked by colour-coded
ellipses and arrows in Figure 6.
Figure 6: Homonuclear j-resolved spectrum of 200 mM ibuprofen in CDCl3 showing th
extra peaks due to strong couplings.
Figure 6: Homonuclear j-resolved spectrum of 200 mM ibuprofen in CDCl3 showing the
extra peaks due to strong couplings.
Figure 6: Homonuclear j-resolved spectrum of 200 mM ibuprofen in CDCl3 showing the
extra peaks due to strong couplings.
1D 13C spectra
spectra
1D 13C SPECTRA 1D 13CThe
C NMR spectra of 2 M ibuprofen in CDCl
13
are shown in Figure 7. Th
experiment is sensitive to all
nuclei in the sample. It clearly resolves 9 r
small triplet between 70 and 80 ppm is from the solvent.
The 13C NMR spectra of 2 M ibuprofen The
in CDCl
in Figure
7. The 1DCarbon
13C DEPT
3 are shown
experiment
uses polarisation
transfer between proton and ca
13
13
butfor
theIt
CH
appear
as negative
in to protons a
experiment
sensitive
to all Cinnuclei
in
clearly
resolves
9 resonances;
the peaks
The C NMR
spectrais of
2 M ibuprofen
CDClcan
2 groups
3 the
be sample.
used
spectral
editing.
Only
carbons
directly
attached
the
DEPT-135.
Through
linear
combination
of
the
triplet7.between
and 80experiment
ppm is from
the
solvent.
are shownsmall
in Figure
The 1D 70
Carbon
these experiments. Since the peaks at 181, 140 and 137 ppm do not show in
The
DEPT
experiment
uses polarisation
transfer
between
proton
and
nucleiThe
and
three
DEPT
spectra
onecarbon
cancarbons.
produce
subspectra
C nuclei
in the sample.
It clearly
is sensitive
to 13
allC13
spectra
they
must
belong
to quaternary
DEPT-90 experiment g
be used forthe
spectral
Only carbons
directly
attached
to
protons
are
visible
in
CHDEPT-45
and
CH
groups
alone,
as
shownof CH, CH2
of thewhilst
CH3, the
of CH groups,
and
DEPT-135
give
signals
resolves 9can
resonances;
smallediting.
triplet between
2
13
but
the
CH
groups
appear
as
negative
peaks
in
the
DEPT-135.
Since theThe
peaksCatDEPT
181, 140 and
137 ppm
do not
show in feature
the DEPT
in 2Figure
7. An
interesting
evident in theseThrough lin
70 and 80these
ppmexperiments.
is from the solvent.
of the three
spectra
onethe
canpeak
produce
subspectra
of the CH3, CH2 and
spectra
must belong
to quaternary
TheDEPT
DEPT-90
gives
only
signal
subspectra
is experiment
that
at 45
ppm
is made
experiment
uses they
polarisation
transfer
between carbons.
alone,
as
shown
in
Figure
7.
An
interesting
feature
evident
in these subspec
of
CH
groups,
whilst
the
DEPT-45
and
DEPT-135
give
signals
of
CH,
CH
and
CH
groups,
up of a CH and a CH2 resonance
proton and carbon nuclei and can be used for
2
3with identical
peak
at
45
ppm
is
made
up
of
a
CH
and
a
CH
resonance
with
identical che
but the Only
CH2 groups
appear
as negative
DEPT-135.
Through linear combination
2
chemical
shifts.
spectral editing.
carbons
directly
attachedpeaks
to in the
of visible
the three
one canSince
produce
protons are
in DEPT
these spectra
experiments.
the subspectra of the CH3, CH2 and CH groups
alone,140
as shown
in ppm
Figuredo7.not
An show
interesting
peaks at 181,
and 137
in feature evident in these subspectra is that the
peak
at
45
ppm
is
made
up
of
a
CH
and
a CH2 resonance with identical chemical shifts.
the DEPT spectra they must belong to quaternary
carbons. The DEPT-90 experiment gives only signal
of CH groups, whilst the DEPT-45 and DEPT-135
give signals of CH, CH2 and CH3 groups,
3
13C
Figure 7: Carbon spectra of 2 M ibuprofen in CDCl3.
Figure 7: Carbon spectra of 2 M ibuprofen in CDCl3.
Figure 7: Carbon spectra of 2 M ibuprofen in CDCl3.
HETCOR
HETCOR
signal along the direct dimension and the proton
Similar to the 2D COSY experiment, which detects
signalproton-proton
along the indirect
dimension.
proton-proton
coupling
series of which detects
Similar
to the partners,
2D COSYaexperiment,
coupling
partners,The
a HETCOR
is
spectrum
of
2
M
ibuprofen
in
CDCl
heteronuclear
2DofNMR
experiments
series
heteronuclear
2D have
NMRbeen
experiments have been devised to detect coupling3 shown in
8, with
the 1D proton
and carbon
spectra
devised topartners
detect coupling
partners
different
of different
nuclei.ofThe
Heteronuclear Figure
Correlation
(HETCOR)
experiment
is used
from
Figures
1
and
7
as
vertical
and
horizontal
nuclei. ThetoHeteronuclear
Correlation
correlate proton
resonances(HETCOR)
to the carbons directly bonded to those protons. The
Thedirect
peaks
in the 2Dand
spectrum
show which
experimentHETCOR
is used to
correlate proton
experiment
detects resonances
the carbon signaltraces.
along the
dimension
the proton
proton
is
bonded
to
which
carbon.
to the carbons
bonded
to dimension.
those protons.
signaldirectly
along the
indirect
The HETCOR
experiment
detects
The HETCOR spectrum the
of 2carbon
M ibuprofen in CDCl3 is shown in Figure 8, with the 1D
proton and carbon spectra from Figures 1 and 7 as vertical and horizontal traces. The peaks
in the 2D spectrum show which proton is bonded to which carbon.
Figure 8: HETCOR spectrum of 2 M ibuprofen in CDCl3.
Figure 8: HETCOR spectrum of 2 M ibuprofen in CDCl3.
HMQC
HMQC
The HMQC spectrum of 2 M ibuprofen in CDCl3 is
Another heteronuclear 2D correlation experiment
Another heteronuclear 2D correlation experiment
is the Heteronuclear Multiple Quantum
shown in Figure 9, with the 1D proton and carbon
is the Heteronuclear Multiple Quantum Coherence
Coherence (HMQC) experiment. Similar to HETCOR,
is used
to correlate
spectra it
from
Figures
1 and 7proton
as horizontal and
(HMQC) experiment. Similar to HETCOR, it is used
resonances to the carbons directly bonded to those
protons.
However,
in
the
HMQC
vertical traces. The peaks in the 2D spectrum show
to correlate proton resonances to the carbons
experiment
the
carbon
signal
appears
along
the
indirect
dimension,
and the
protoncarbon.
signal A similar
which
proton
is bonded
to which
directly bonded to those protons. However, in
along the direct dimension.
analysis as with the HETCOR spectrum can be
the HMQC experiment the carbon signal appears
in Figure
9, with
theassignment.
1D proton
The
HMQC
spectrum
of
2
M
ibuprofen
in
CDCl
3 is shownfor
performed
conclusive
peak
along the indirect dimension, and the proton signal
carbon
spectra from Figures 1 and 7 as horizontal and vertical traces. The peaks in the
along the and
direct
dimension.
2D spectrum show which proton is bonded to which carbon. A similar analysis as with the
HETCOR spectrum can be performed for conclusive peak assignment.
Figure 9: HMQC spectrum of 2 M ibuprofen in CDCl3.
Figure 9: HMQC spectrum of 2 M ibuprofen in CDCl3.
HMBC
The HMQC experiment shown on the previous page was designed to correlate p
carbons which are connected through a one bond coupling. To obtain long-range
carbon correlations through two or three bond couplings, the Heteronuclear Mul
Correlation (HMBC) experiment can be used. Like in the HMQC experiment the
signal appears along the indirect dimension, and the proton signal along the dire
dimension.
HMBC
The HMBC spectrum of 1 M ibuprofen in CDCl3 is shown in Figure 10, with the
HMQC
additionally
couplings
to
The HMQC experiment shown on the and
previous spectrathe
Figures
1 andto7correlate
asshows
horizontal
The HMQC experiment showncarbon
on the previous from
page was
designed
protonsand
andvertical traces. The pe
quaternary
carbons,
which are
not
visible
in the
page was designed
to which
correlate
protons
2Dand
spectrum
show
which
protons
are connected
toprotonwhich
carbons
via a long-ran
carbons
are connected
through
a one
bond
coupling.
To obtain
long-range
COSY
or
HMQC.
For
example,
there
are
clear
carbons which are
connected
through
a
one
bond
carbon correlations through
two or three
couplings,
the Heteronuclear
Multiple Bond
coupling.
Thebond
couplings
between
molecular positions
look similar to the ones fo
couplings
from the
protons
at positions
coupling. To obtain
long-range
protoncarbon
Correlation
(HMBC)
experiment
can be
used.multibond
Like
the HMQC
HMQC
experiment
theshows
carboncouplings
the COSY
spectrum,
butinthe
additionally
to quaternary
2
and
13
to
the
carbon
at
position
1,
as
correlations through
two
or
three
bond
couplings,
signal appears along the indirect
and the
proton
signaloralong
the direct
which dimension,
are not visible
in the
COSY
HMQC.
For example, marked
there areinclear multi
dimension.
10.atItpositions
is also interesting
note
that at
there
is 1, as m
the Heteronuclear
Multiple Bond Correlation
couplings from theFigure
protons
2 and 13 totothe
carbon
position
is shown inbetween
Figure 10,carbons
with the 1D
proton
The HMBC
of 1 M
ibuprofen
in CDCl
a
correlation
(11,12)
to
protons
(HMBC) experiment
can bespectrum
used. Like
in
the
3
Figure 10.
and carbon
spectrasignal
from Figures
1 and
7 as horizontal
and
vertical
The peaks in
the
(11,12).
This
isthere
duetraces.
coupling
from 11(11,12) to
HMQC experiment
the carbon
appears
along
Itprotons
is alsoare
interesting
to
note
that
istoaathree-bond
correlation between
carbons
2D
spectrum
show
which
connected
to
which
carbons
via
long-range
to
12
and
vice
versa
(light
green).
the indirect dimension, and the proton(11,12).
signal along
This is due
to three-bond
coupling
fromfound
11 tofrom
12 and vice versa (light gr
coupling. The couplings between molecular
positions
look similar
to the ones
HMBC
the direct dimension. The HMBC spectrum of 1 M
the COSY spectrum, but the HMQC additionally shows couplings to quaternary carbons,
shown
in Figure
withorthe
ibuprofen in CDCl
3 is are
which
not visible
in the10,
COSY
HMQC. For example, there are clear multibond
1D proton and carbon
Figures
1 and2 and 13 to the carbon at position 1, as marked in
couplingsspectra
from thefrom
protons
at positions
7 as horizontal and
vertical
traces. The peaks in the
Figure
10.
2D spectrum show
which
protonstoare
It is also
interesting
noteconnected
that there is a correlation between carbons (11,12) to protons
(11,12).
is due to coupling.
three-bond The
coupling from 11 to 12 and vice versa (light green).
to which carbons
via aThis
long-range
couplings between molecular positions look similar
to the ones found from the COSY spectrum, but
Figure 10: HMBC spectrum of 2 M ibuprofen in CDCl3, with some of the long-ra
couplings marked.
Figure 10: HMBC spectrum of 2 M ibuprofen in CDCl3, with some of the long-range
Figure
10: HMBC
spectrum of 2M ibuprofen in CDCl3.
couplings
marked.
R
Specifications
• Frequency: 42.5 MHz Proton, 10.8 MHz Carbon
• Resolution: 50% linewidth < 0.7 Hz (16 ppb)
• Lineshape: 0.55% linewidth < 20 Hz
• Dimensions: 58 x 43 x 40 cm
• Weight: 55 kg
• Magnet: Permanent and cryogen free
• Stray field: < 2 G all around system
Other Spinsolve products
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R
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• 1D Proton only system
• 1H and 19F nuclei
• Budget friendly price
• Relaxation time experiments
• Upgradeable
• 2D COSY and JRES
• Reaction monitoring
“Now the students are able to acquire their own NMR spectra as well as carry out the analysis of the compounds they
have made. This makes their undergraduate experiment more applicable to both research and industry settings and
increases their enthusiasm for Chemistry.”
Professor Frances Separovic, Head of Chemistry, University of Melbourne
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