Exercise plus Solution – Quick overview
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Deduce the structure without worrying
care about the coupling patterns in the
proton spectrum!
C
4
H
8
O measured in CDCl
3
1
H NMR spectrum
measured at 250.13 MHz
13
C{
1
H} NMR spectrum
measured at 62.90{250.13} MHz
1
H/
13
C HSQC
measured at 250.13/62.90 MHz
1
H/
1
H COSY
measured at 250.13 MHz
C C
O
CH
2
CH
3
H
H
H
Solution
Step-by-Step
1 1 1 2 3
2.9
2.75
2.49
1.59
1.01
53.4
46.8
25.4
9.7
from
1
H
spectrum
from
13
C
spectrum
If available, an HSQC is nearly always the
best starting point for a structure
elucidation.
As a first step it is recommended to collect
the integrals and chemical shifts from the
one-dimensional spectra.
1 1 1 2 3
2.9
2.75
2.49
1.59
1.01
53.4
46.8
25.4
9.7
C H
H
H
1.01
9.7
C H
H
H
1.01
9.7
from
1
H
spectrum
from
13
C
spectrum
Now one can determine the CH
n
fragments
from the cross peaks and the integrals one
after the other.
For the moment this results in a disordered
collection of building blocks.
C
H
H
1.59
25.4
1 1 1 2 3
2.9
2.75
2.49
1.59
1.01
53.4
46.8
25.4
9.7
C
H
H
1.59
25.4
C H
H
H
1.01
9.7
Now one can determine the CH
n
fragments
from the cross peaks and the integrals one
after the other.
For the moment this results in a disordered
collection of building blocks.
1 1 1 2 3
2.9
2.75
2.49
1.59
1.01
53.4
46.8
25.4
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
H
2.49/
2.75
46.8
C H
H
H
1.01
9.7
Now one can determine the CH
n
fragments
from the cross peaks and the integrals one
after the other.
For the moment this results in a disordered
collection of building blocks.
1 1 1 2 3
2.9
2.75
2.49
1.59
1.01
53.4
46.8
25.4
9.7
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
2.9
53.4
Now one can determine the CH
n
fragments
from the cross peaks and the integrals one
after the other.
For the moment this results in a disordered
collection of building blocks.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
2.9
53.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
As a first step let us reorder the building blocks by
their proton chemical shifts and put them close to
the corresponding proton signals in the projection.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
As a first step let us reorder the building blocks by
their proton chemical shifts and put them close to
the corresponding proton signals in the projection.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
H
1.59
25.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
As a first step let us reorder the building blocks by
their proton chemical shifts and put them close to
the corresponding proton signals in the projection.
C H
H
H
1.01
9.7
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
As a first step let us reorder the building blocks by
their proton chemical shifts and put them close to
the corresponding proton signals in the projection.
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
As a first step let us reorder the building blocks by
their proton chemical shifts and put them close to
the corresponding proton signals in the projection.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
2.9
53.4
C
H
H
2.49/
2.75
46.8
C
H
H
1.59
25.4
C H
H
H
1.01
9.7
The methyl group clearly is one end of the molecule.
We use the methyl group to start the sequential
ordering of the building blocks.
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
2.9
53.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
H
1.59
25.4
C
H
2.9
53.4
C
H
H
2.49/
2.75
46.8
C
H
H
1.59
25.4
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
The next building block has to be attached to the
ethyl group found so far.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
C
H
2.9
53.4
C
H
H
2.49/
2.75
46.8
Let us switch to the COSY now and combine
the building blocks using their proton
chemical shifts.
There is only one way to attach the final methylene
group. Because this group contains two
diastereotopic protons, we observe two cross peaks
in the COSY.
C H
H
H
1.01
9.7
C
H
H
1.59
25.4
C
H
H
2.49/
2.75
46.8
C
H
2.9
53.4
We are left with one unassigned oxygen and
two open bonds, both of which we can
accommodate in …
C C
O
CH
2
CH
3
H
H
H
