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3122
Subject
Chemistry
Date
Jan 9, 2024
Type
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16
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1
1. A student carries out the transformations shown below to elucidate the stereochemistry of
compound
A
, an intermediate in the synthesis of a complex natural product. Using the spectra
of compound
B
, knowledge of the chemical sequence, and the NOE data supplied, perform the
following operations:
a. Assign all of the resonances in the spectrum
b. Determine as many coupling constants as possible, and report your data in ACS format
c.
Deduce the relative configuration at as many positions as possible in products
A
and
B
.
O
HO Me
HO
OH
Me
Me
OEt
A
B
O
I
2
, NaHCO
3
I
CO
2
Et
1) Ac
2
O, py
2) Bu
3
SnH
AIBN,
O
AcO Me
CO
2
Et
Decoupling the signal at 1.20 ppm reduces the signal at 2.81 to a doublet with J = 6.3 Hz
Decoupling the signal at 0.90 ppm reduces the signal at 2.60 to a dd with J = 5.4, 4.5 Hz
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
ppm
4.35
ppm
2149.190
2151.881
2153.698
2156.381
2158.190
2160.880
2174.323
2179.714
2180.337
2185.723
3.80
3.85
ppm
1886.654
1890.976
1896.954
1901.275
1914.531
1917.201
1924.829
1927.500
2.75
2.80
2.85
ppm
1391.927
1398.588
1404.951
1411.437
1418.120
2.60
2.65
ppm
1284.094
1289.273
1291.373
1294.143
1296.440
1298.668
1301.383
1303.612
1305.944
1308.674
1310.811
1315.987
2
3
Proton
NOE
A
4.36
D
(7%),
G
(2%),
F
(7%),
I
(6 %)
B
4.31
D
(2 %),
E
(5 %),
G
(5 %),
H
(6 %),
K
(3 %)
C
3.99
F
(4 %),
I
(3 %),
J
( 9%)
D
3.84
A
(6 %),
B
(2 %),
E
(9 %)
E
3.79
B
(5 %),
D
(9 %),
G
(3 %)
F
2.81
A
(7 %),
C
(4 %),
I
(9 %)
G
2.60
A
(2 %),
B
(5 %),
E
(3 %),
K
(6 %)
H
1.98
B
( 5 %)
I
1.16
A
(5 %),
F
(9 %)
J
1.01
C
(8 %)
K
0.90
A
(8 %),
B
(2.5 %),
G
(7 %)
4
5
2. A student continues the same synthesis, and carries out the transformations shown below to
elucidate the stereochemistry of intermediate
X
. Using the spectral data for compound
Y
, and
knowledge of the chemical sequence, deduce the missing stereochemistry in product
X
a. Assign all of the resonances in the spectrum
b. Determine as many coupling constants as possible, and report your data in ACS format
c.
Deduce the stereochemistry at as many positions as possible in product
X
(you will need
the results of question 11 for this).
O
MeO Me
OAc
Me
Me
2
BBr
Br
MeO
Me
OH
Me
OAc
1) HSnBu
3
2) NaOH, MeOH
3) PCHO, H
+
MeO
Me
O
Me
O
Ph
X
Y
1
H NMR (500 MHz, C
6
D
6
)
A
: 7.32-7.09 (m, 5H)
B
: 5.40 (s, 1H)
C
: 3.99 (dd, J = 13.1, 11.0 Hz, 1H)
D
: 3.86 (dd, J = 13.1, 4.6 Hz, 1H)
E
: 3.46 (quint, J = 6.6 Hz, 1H)
F
: 3.29 (dd, J = 10.1, 3.7 Hz, 1H)
G
: 3.14 (s, 3H)
H
: 2.20-2.14 (m, 1H)
I
: 2.15-2.07 (m, 1H)
J
: 1.65 (d, J = 6.5 Hz, 3H)
K
: 1.20 (d, J = 6.3 Hz, 3H)
L
: 1.12 (d, J = 6.7 Hz, 3H).
Decoupling the signal at 1.20 ppm (
K
) simplifies the signal at 2.15-2.07 (
I
) (1077.30
–
1032.7
Hz) to a multiplet from 1067.85 to 1042.15 Hz.
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Related Questions
Part 3B Set 1. Can 1H NMR spectroscopy be used to differentiate between the two compounds? Briefly explain why or why not. Predict the 1H NMR spectrum for each compound (include integration, multiplicity, and approximate chemical shift). Either draw the actual spectrum or put in a data table format.
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[Review Topics)
[References]
Draw the structure of the compound C3HgS from its proton (¹H) NMR spectrum below.
First-order spin-spin splitting rules and equal coupling constants can be assumed. (Detailed analysis of any non-first
order portions of the spectrum will not be required.)
Integral ratios to the nearest whole number are (left to right) 2:3:3.
Used with permission from Aldrich Chemical Co., Inc.
Solvent COC
9.0
7.5
6.0
4.5
Chemical shift, & (pp)
ille
0.0
Previous
Next
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The following H-NMR spectrum (showing all available signals) is for one of the possible products listed below. This
product was obtained from oxidizing one of the alcohols listed below (as possible reactants) using either dichromate
(Na2Cr2O7/H2SO4) or DMP. Determine the product, reactant and oxidizing agent following the analysis below.
Based on the given H-NMR spectrum, and since there is
signals is
and the total number of H-NMR
the oxidation product must be
÷
Therefore, the oxidizing agent
and the reactant must be
PPM
Possible Reactants
OH
A
Possible Products
O
I
V
ОН
B
ОН
VI
II
ОН
C
ОН
OH
III
VII
OH
D
OH
E
IV
VIII
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structures.
a) C3H10
1.2 8 (3H, triplet)
2.6 8 (2H, quartet)
7.1 8 (5H, broad singlet)
b) C4H7BrO
2.11 8 (3H, singlet)
3.52 8 (2H, triplet)
4.40 8 (2H, triplet)
Cs Scanned with CamScanner
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Considering that each of the derivatives contains AT MOST two substituents (X and/or Y) and at least two protons.
A) Propose the possible substitution patterns for each of the derivatives based on the observed splitting patterns. Justify your proposals
B) How might one differentiate between the three possible isomers of derivative 3 in the question above using 1H NMR spectroscopy? Explain in a sentence – no calculation is needed.
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Show how you will prepare PVB from PVA.
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13
and N.
Conmoud M
Chaacal Sh
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ORGANIC CHEMISTRY
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(a) Provide the bond line structures
(b) Indicate the number of peaks that would be seen in their ¹H-NMR
spectra. Number each unique type of hydrogen peaks as shown in the
example on the right.
(c) Label the diasterotopic and enantiotopic atoms and/or groups.
1. (1R,4S) 4-secbutyl-2,3-diethyl-6,6-dimethylcyclohex-2-enol
2. (2R,6S) 2,6-dibromo-4,4-dimethylcyclohexanol
Example: ¹H
2
O
2
1
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what is the structure of these compounds and assign their data whilst talking about their couplings
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and 13C NMR). Note that in some cases a given technique will provide no means to distinguish the compounds. Please write
about all four techniques in your answer.
Br
Br
vs.
çO,H
çO,Me
vs.
čO,Me
CO2H Br
Он
Он
vs.
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1. COMPOUND CSH100 (pent-2-en-1-ol)
A) PREDICT THE UV-VIS SPECTRUM OF THIS COMPOUND AND EXPLAIN.
B) CALCULATE THE CHSNO COMPOUND
Element
Calculated (%)
Carbon
69.72
Hydrogen
Nitrogen
Охудеn
Total (%)
11.70
0.00
18.58
100
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and 13C NMR). Note that in some cases a given technique will provide no means to distinguish the compounds. Please write
about all four techniques in your answer.
Br
Br
vs.
Br
CO,H
çO2Me
vs.
čO,Me
CO2H Br
OH
OH
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Нас
3. (5S,7R) -7-bromo-3,9-diethyl-6,6-dimethylundec-3,8-dien-5-ol
H C
Н.С
Ay statuvos
OH
CH3
Ay si
Br
Н
CH3
CH3
I
b. number of peaks =
С.
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Draw the
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OCH3
b.) dil. aq. HCI
infrared assignments:
absorption (cm')
assignment
3550
3050
2930
1600
1570
1490
1450
1150
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—|-
10
1H
9
8
6
7
Chemical Shift (ppm)
1H
5
2H
3
2H
2
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Related Questions
- Part 3B Set 1. Can 1H NMR spectroscopy be used to differentiate between the two compounds? Briefly explain why or why not. Predict the 1H NMR spectrum for each compound (include integration, multiplicity, and approximate chemical shift). Either draw the actual spectrum or put in a data table format.arrow_forward[Review Topics) [References] Draw the structure of the compound C3HgS from its proton (¹H) NMR spectrum below. First-order spin-spin splitting rules and equal coupling constants can be assumed. (Detailed analysis of any non-first order portions of the spectrum will not be required.) Integral ratios to the nearest whole number are (left to right) 2:3:3. Used with permission from Aldrich Chemical Co., Inc. Solvent COC 9.0 7.5 6.0 4.5 Chemical shift, & (pp) ille 0.0 Previous Nextarrow_forwardExplain in detail how the spectroscopic data shows that cyclohexanol, the reactant, produced the expected product, cyclohexene. Is the product pure? How do you know? Refer to specific frequencies in the IR spectrum and specific signals in the NMR spectra to support your conclusion.arrow_forward
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Recommended textbooks for you
- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage Learning
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ISBN:9780618974122
Author:Andrei Straumanis
Publisher:Cengage Learning