Question

4. Assume that the 1H NMR spectrum shown below was obtained on your isolated reaction product. Note that the frequency range of the original spectrum was -0.5 – 12 ppm, but the downfield range (~8.5 – 12 ppm) and upfield (< 4 ppm) were deleted in the printout because no signals were detected on those regions. a) Draw the chemical structure of the ?-hydroxyketone intermediate. b) Is there any ?-hydroxyketone contained in your reaction product? Why or why not? Refer to your drawn structure as necessary. 2H 1H 2H 5H 1H 8 7 ? (ppm) 6 5 5. Shown below is the peak list of chemical shifts (ppm), multiplicities / coupling constants, number of protons (noted at the top of each signal), for the 1H NMR spectrum in Question 4. a) Draw the chemical structure of trans-4-nitrochalcone. Assign letters to all the protons. Circle the proton or protons that you would attempt to identify in the 1H NMR spectrum as evidence that the expected trans-isomer was formed (rather than the cis-isomer). b) Complete the information missing in the table. Identify the peak or peaks in the peak list that correspond(s) to the proton or protons circled in part (a). What specific information would verify the alkene stereochemical assignment? 1H NMR spectrum of trans-4-nitrochalcone Proton(s) in Peak Peak Multiplicity Peak Integration Molecule (letters Frequency (s, d, etc.) (Number of Protons) assigned in figure) (ppm) 8.15 d, J = 8.5 7.98 J = 15.7 Hz 7.85 d, J = 8.5 7.51 m (multiplet) 6.98 J = 15.7 Hz

          4. Assume that the 1H NMR spectrum shown below was obtained on your isolated reaction
product. Note that the frequency range of the original spectrum was -0.5 – 12 ppm, but the
downfield range (~8.5 – 12 ppm) and upfield (< 4 ppm) were deleted in the printout because
no signals were detected on those regions.
a) Draw the chemical structure of the ?-hydroxyketone intermediate.
b) Is there any ?-hydroxyketone contained in your reaction product? Why or why not? Refer to
your drawn structure as necessary.
2H 1H 2H
5H
1H
8
7
? (ppm)
6
5
5. Shown below is the peak list of chemical shifts (ppm), multiplicities / coupling constants,
number of protons (noted at the top of each signal), for the 1H NMR spectrum in Question 4.
a) Draw the chemical structure of trans-4-nitrochalcone. Assign letters to all the protons.
Circle the proton or protons that you would attempt to identify in the 1H NMR spectrum as
evidence that the expected trans-isomer was formed (rather than the cis-isomer).
b) Complete the information missing in the table. Identify the peak or peaks in the peak list
that correspond(s) to the proton or protons circled in part (a). What specific information
would verify the alkene stereochemical assignment?
1H NMR spectrum of trans-4-nitrochalcone
Proton(s) in
Peak
Peak Multiplicity
Peak Integration
Molecule (letters
Frequency
(s, d, etc.)
(Number of Protons)
assigned in figure)
(ppm)
8.15
d, J = 8.5
7.98
J = 15.7 Hz
7.85
d, J = 8.5
7.51
m (multiplet)
6.98
J = 15.7 Hz

4. Assume that the 1H NMR spectrum shown below was obtained on your isolated reaction
product. Note that the frequency range of the original spectrum was -0.5 – 12 ppm, but the
downfield range ( 8.5 – 12 ppm) and upfield (< 4 ppm) were deleted in the printout because
no signals were detected on those regions.
a) Draw the chemical structure of the ?-hydroxyketone intermediate.
b) Is there any ?-hydroxyketone contained in your reaction product? Why or why not? Refer to
your drawn structure as necessary.
2H 1H 2H
5H
1H
8
7
? (ppm)
6
5
5. Shown below is the peak list of chemical shifts (ppm), multiplicities / coupling constants,
number of protons (noted at the top of each signal), for the 1H NMR spectrum in Question 4.
a) Draw the chemical structure of trans-4-nitrochalcone. Assign letters to all the protons.
Circle the proton or protons that you would attempt to identify in the 1H NMR spectrum as
evidence that the expected trans-isomer was formed (rather than the cis-isomer).
b) Complete the information missing in the table. Identify the peak or peaks in the peak list
that correspond(s) to the proton or protons circled in part (a). What specific information
would verify the alkene stereochemical assignment?
1H NMR spectrum of trans-4-nitrochalcone
Proton(s) in
Peak
Peak Multiplicity
Peak Integration
Molecule (letters
Frequency
(s, d, etc.)
(Number of Protons)
assigned in figure)
(ppm)
8.15
d, J = 8.5
7.98
J = 15.7 Hz
7.85
d, J = 8.5
7.51
m (multiplet)
6.98
J = 15.7 Hz

Added by Jorge M.

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