Chem 344 – University of Wisconsin
Chemistry 344: Spectroscopy and Spectrometry Problem Set 2
Name (print): _______________________________________
TA Name (print): ____________________________________
I.
For each of the molecules below, predict the splitting pattern and chemical shift using CurphyMorrison parameters and/or a chemical shift table for each of the signals in the 1H-NMR spectrum.
Make a rough sketch on the horizontal ppm axis provided. Be sure to consider the relative intensity
of each signal and label its integration. Draw a TMS signal and label it on each spectrum.
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Chem 344 – University of Wisconsin
For the IR, EI-Mass, 1H-NMR and 13C-NMR spectra shown below of propyl acetate (C5H10O2), analyze
the structure and each of the spectra as instructed.
II.
A. For the IR spectrum below of propyl acetate, label the absorptions for the C(sp3) – H, a C – O, and
the C=O bond stretches.
B.
For the EI-MS shown below of propyl acetate, provide an electron-pushing mechanism that accounts
for the generation of the base peak ion, m/z = 43 from the molecular ion of propyl acetate.
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Chem 344 – University of Wisconsin
C. In the 13C-NMR spectrum of propyl acetate shown below, label the hybridization of each 13C-atom
signal and state the number of different 13C-atom environments. Additionally, label the likely
functional group of each 13C-atom signal and the peaks due to 13CDCl3 and [13C]-TMS.
75 MHz ¹³C NMR
In CDCl3
21.995
66.068
10.383
20.976
77.146
76.726
77.567
0.000
171.162
160
140
120
100
80
60
40
20
0
D. Before analyzing the 1H-NMR spectrum
on the
subsequent page,
© 2015,
Sigma-Aldrich
Co. estimate the chemical shift of each
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H-atom in propyl acetate. Additionally,
the
coupling pattern and integration value that
should be observed for each signal.
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Chem 344 – University of Wisconsin
E. Assign each of the signals in the 1H-NMR spectrum below to their corresponding 1H-atoms in propyl
acetate. Use the designations provided under each signal in your assignments.
300 MHz ¹H NMR
In C DC l3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
3.02
3.00
0.2
2.04
2.00
0.3
0.1
0.0
A
4.0
B
3.5
3.0
C
D
2.5
2.0
1.5
1.0
0.5
0.0
© 2013, Sigma-Aldrich Co.
F. How would you expect the 1H-NMR spectrum
of methyl
butyrate to differ? Be specific and include a
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rough sketch of the spectrum.
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Chem 344 – University of Wisconsin
III.
The 13C-NMR and 1H-NMR spectra of p-diisopropylbenzene are shown below; analyze the structure
and each of the spectra as instructed.
A. In the 13C-NMR spectrum of p-diisopropylbenzene shown below, label the hybridization of each 13Catom signal and state the number of different 13C-atom environments. Additionally, label the likely
functional group of each 13C-atom signal and the peaks due to 13CDCl3 and [13C]-TMS.
75 MHz ¹³C NMR
In CDCl3
126.249
24.049
33.672
146.110
76.564 77.405
76.985
0.000
0
20
40
60
80
© 2015, Sigma-Aldrich Co.
RESERVED
ALL RIGHTS
B. Despite 12 C-atoms in p-diisopropylbenzene,
its spectrum
shows only four 13C-NMR environments.
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Explain how the structure results in so few C-NMR signals. How many 1H-NMR signals would you
expect to observe?
140
120
100
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Chem 344 – University of Wisconsin
C. Assign each of the signals in the 1H-NMR spectrum below to their corresponding 1H-atoms in pdiisopropyl benzene. Use the designations provided under each signal in your assignments.
300 MHz ¹H NMR
In C DC l3
1.2
1.1
1.0
0.9
0.8
0.7
B
12.04
0.6
0.5
0.4
C
0.3
3.95
0.2
2.00
0.1
0.0
A
B
7
6
5
C
4
3
2
1
0
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RESERVED
D. For the signal labeled B shown below, ALL
label RIGHTS
the approximate
signal intensities for each individual
peak. Provide an explanation for the observed intensities.
B
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IV.
For a molecule with a chemical formula of C3H4Br2O, answer the following questions.
A. What is the unsaturation number (U) or index of hydrogen deficiency (IHD)? What does this
indicate about which functional groups or structural units are possible for this molecule?
𝑈 = 𝐼𝐻𝐷 =
2𝐶 + 2 + 𝑁 − 𝐻 − 𝑋
2
B. The 1H-NMR spectrum of C3H4Br2O is provided below. Draw part structures that account for the
integration and coupling observed in each signal.
300 MHz ¹H NMR
In C DC l3
1.2
1.1
1.0
0.9
0.8
0.7
3.16
0.6
0.5
0.4
0.3
1.00
0.2
0.1
0.0
A
B
5
4
3
2
1
0
C. Based upon the part structures drawn©
in2013,
part BSigma-Aldrich
and the relative
Co.chemical shifts of each signal, draw
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two potential molecules, one carbonylALL
containing
molecule
and one epoxide. Label the 1H-atoms in
each structure as Ha and Hb.
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Chem 344 – University of Wisconsin
D. The identity of the correct C3H4Br2O molecule can be confirmed in several independent techniques.
Explain how each piece of evidence presented below can confirm the identity of the correct
molecular structure.
75 MHz ¹³C NMR
In CDCl3
21.882
52.725
166.067
76.564
77.421
77.001
0.000
160
140
120
100
80
60
© 2015, Sigma-Aldrich Co.
ALL RIGHTS RESERVED
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SDBSWeb : http://sdbs.riodb.aist.go.jp (National Institute of Advanced Industrial Science and
Technology)
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Chem 344 – University of Wisconsin
SDBSWeb : http://sdbs.riodb.aist.go.jp (National Institute of Advanced Industrial Science and
Technology)
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Chem 344 – University of Wisconsin
V.
For a molecule with a chemical formula of C12H19N, answer the following questions.
A. What is the unsaturation number (U) or index of hydrogen deficiency (IHD)? What does this
indicate about which functional groups or structural units are possible for this molecule?
𝑈 = 𝐼𝐻𝐷 =
2𝐶 + 2 + 𝑁 − 𝐻 − 𝑋
2
B. Using the 1H-NMR and 13C-NMR spectra below, identify the molecule and fully analyze the NMR
spectra.
300 MHz ¹H NMR
In C DC l3
1.2
1.1
1.0
0.9
0.8
0.7
A
B
0.6
0.5
9.19
0.4
6.11
0.3
0.2
2.03
2.06
0.1
0.0
A
8
B
7
C
6
5
4
3
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D
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Chem 344 – University of Wisconsin
75 MHz ¹³C NMR
In CDCl3
31.505
125.763
112.550
40.805
77.405
76.985
148.487
139.284
140
76.564
33.705
0.000
120
100
80
60
40
20
0
© 2015, Sigma-Aldrich Co.
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RESERVED
C. The 13C-NMR signals at 148.487 and 139.284
ppm are
much smaller than the neighboring signals at
125.763 ppm and 112.550 ppm. Provide two reasons that the signals at 148.487 and 139.284 ppm
are lower in amplitude.
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Chem 344 – University of Wisconsin
VI.
Determine the structure of the molecule with formula C9H10 that corresponds to the spectra shown
below. Fully analyze each spectrum.
300 MHz ¹H NMR
In C DC l3
1.2
1.1
1.0
0.9
4.00
1.99
1.99
1.87
0.8
0.7
C
A
D
0.6
B
0.5
0.4
4.00
0.3
0.2
1.99
0.1
0.0
C
A-B
7
D
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6
5
3
4
© 2013, Sigma-Aldrich Co.
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Chem 344 – University of Wisconsin
75 MHz ¹³C NMR
In CDCl3
32.880
125.941
124.308
25.343
144.056
77.001
77.421
76.580
0.000
140
120
100
80
60
© 2015, Sigma-Aldrich Co.
ALL RIGHTS RESERVED
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Chem 344 – University of Wisconsin
VII. Using the 1H-NMR spectrum and questions below, determine the relative amount of acetone and
isopropyl alcohol in a mixture of the two molecules. For more information on determining ratios
by 1H-NMR. (https://www.chem.wisc.edu/content/experiment-6-elimination-reactions-e1e2#Q1)
A. For each of the molecules shown below, identify the likely observed coupling pattern and
estimate the likely chemical shift.
B. Assign each of the signals in the 1H-NMR spectrum below to their corresponding 1H-nuclei in
the molecules above using the letter designations A-D.
C. Using the spectrum below, determine the relative amount of acetone and isopropyl alcohol in
the spectrum of a mixture relative to the least abundant molecule. Report the ratio with the
lowest abundance species set to a value of 1.00.
A
B
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C
D
Chem 344 – University of Wisconsin
VIII.
Determine the structure of the molecule with formula C5H9ClO that corresponds to the spectra
shown below. Fully analyze each spectrum.
B
A
B
C
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Chem 344 – University of Wisconsin
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Chem 344 – University of Wisconsin
IX.
Determine the structure of the molecule with formula C4H7ClO2 that corresponds to the spectra
shown below. Fully analyze each spectrum.
B
C
A
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