OChem2 Course Pack
Practice Problems by Chapter
Practice Exams
Chemistry 3720 Problem Sets Chemistry 3720
Ch. 13-19 Synthesis Problems
These problems are typical of those that will be on the upcoming exams in 3720.
1. From Chapters 13-19: Show retrosynthetic analyses for each of the following molecules that go back
only to the starting materials given below. Then, using any chemistry seen in 3719 and 3720 so far,
give an efficient synthesis of each molecule showing the products formed in each step. Assume that
you have access to any of the usual reagents such as Br2, AlCl3, Fe, HBr, HNO3, H2SO4, etc.
a.
d.
OH
b.
OH
e.
OH
OH
c.
OH
O2N
start ing mater ials
O
CH 3Cl
H
O
Br
O
Cl
2. From 13 and 14: Give structures of the products from each step within the following “roadmap” and
match the spectral data to the product.
O
Na2Cr 2O 7
H 3O+
H 2SO 4
H2O
(13C 200 ppm)
H
Mg, ether
Br2, heat
(IR 3300 cm-1)
3. From 13-19: Give structures of the products from each step in the following reaction sequences.
a.
1. Br 2, heat
2. 2 Li, ether
3. CH 3CHO
4. H 3O +
5. HBr
b.
1. CH3COCl, AlCl3
2. LiAlH 4, ether
3. H 3O +
4. NaH, ether
5. CH 3CH 2Br
c.
O
1. NaBH4, CH3OH
2. HBr
3. 2 Li, ether
4. CH 3CH 2CHO
5. H3O+
d.
1. H2SO4, H2O
2. Na 2Cr2O7, H 2SO 4
3. PhMgBr, ether
4. H 3O +
5. NaH, ether
6. CH 3CH2CH 2Br
e.
OH
1. PDC, CH2Cl2
2. CH 3Li, ether
3. H3O+
4. Na2Cr 2O7, H2SO4
5. PhMgBr, ether
6. H 3O +
f.
1. CH 3COCl, AlCl3
2. HNO3, H2SO4
3. NaBH 4, CH 3OH
4. NaH, ether
5. CH3CH 2CH 2Br
4. From 1-19: Design syntheses of the following molecules using any of the chemistry seen so far in
3719 and 3720 and using only the sources of carbon shown below. Again, assume that you have
access to all of the common inorganic reagents (Br2, AlCl3, Fe, HBr, etc.).
a.
O
O
HO
Cl
NH 2
b.
HO
OH
OH
c.
O
O
OH
CH 3Br
d.
O
Br
H
H
e.
OH
CH3 CH 2 OH
OCH3
Chemistry 3720
ChapterV 16 - Spectroscopy Problems
1. (10 pts) An unknown organic compound has the molecular formula C5H12O, in the mass spectrum, M+
= 88.09. Given the following 1H and 13C data, give the structure of the unknown and assign all of the 1H
and 13C signals.
4
1
3
2
PPM
1
0
H NMR (ppm) 1.14 (t, 3H, J = 7.2 Hz), 1.09 (d, 6H, J = 7.0 Hz), 3.19 (septet, 1H, J = 7.0 Hz),
3.50 (q, 2H, J = 7.2 Hz)
70
60
13
50
40
PPM
30
20
C NMR (ppm) 15.5, 22.3 (double), 64.8, 71.8
1
10
0
2. (10 pts) Draw the approximate 13C NMR spectrum of the following molecule. Include approximate
chemical shifts and indicate which signal corresponds to which carbon(s) in the molecule.
O
O
H3C
O
O
CH 3
3. (10 pts) A chemist produces a new compound with the following spectral characteristics and considers
the new material to be one of the possibilities shown below. Which structure is correct and why?
Include a complete assignment of all of the spectral data in your answer.
1
H NMR (ppm)
13
1.32 (t, 3H, J = 7.0 Hz), 3.30 (s, 3H,), 4.09 (q, 2H, J = 7.0 Hz), 4.63 (s, 2H), 7.10
(m, 2H), 7.83 (m, 2H)
C NMR (ppm)
14.8, 57.2, 64.6, 81.2, 126.1, 129.4 (double), 129.7 (double), 163.8, 198.3
IR (cm-1)
1740, 810
O
O
OCH3
OCH 3
O
O
O
OH
O
OCH 3
OH
O
O
O
O
O
O
2
O
4. (10 pts) Draw the expected 1H and 13C NMR spectra of the following molecules. Include chemical
shifts and line shapes (singlet, doublet, etc.) in the 1H spectra and intensities in the 13C spectra. Also
indicate which signal corresponds to which proton(s) and carbon(s).
a.
O
O
b.
O
O
c.
O
O
d.
O
O
5. (10 pts) An unknown organic compound has the molecular formula C11H14O2. Given the following
spectral data, provide a structure for the unknown that agrees with the data, and then assign the data.
1
H NMR (ppm)
13
C NMR (ppm)
2.50 (s, 3H), 2.75 (t, 2H, J = 7.2 Hz), 3.30 (s, 3H), 2.52 (t, 2H, J = 7.2 Hz), 7.377.76 (m, 4H)
26.6, 35.3, 59.3, 73.0, 126.0, 127.7, 128.5, 132.1, 1391, 139.2, 197.0
Mass spectrum (m/z) 178.10 (M+)
Infra Red (cm-1)
1730, 760, 690
6. (10 pts) An unknown organic compound has the molecular formula C12H16O2 and, in the mass
spectrum, M+ = 192.12. Given the following 1H and 13C data, give the structure of the unknown and
then assign all of the 1H signals.
1
H NMR (ppm)
13
C NMR (ppm)
1.20 (d, 6H, J = 7.0 Hz), 1.29 (t, 3H, J = 7.1 Hz), 2.87 (septet, 1H, J = 7.0 Hz),
4.30 (q, 2H, J = 7.1 Hz), 7.41 (d, 2H), 7.97 (d, 2H)
14.1, 23.3 (double), 33.2, 60.9, 126.0 (double), 127.3, 129.6 (double), 155.7,
165.9
3
Chemistry 3720
Chapter 19 - Benzene Synthesis Problems
Provide an efficient synthesis of each of the following substituted benzenes from benzene
itself. Use any of the reagents seen in Chemistry 3719/3720 so far and pay careful
attention to the order of steps. Assume that mixtures may be separated.
CH3
O
Br
CO 2H
NH2
SO3H
CO 2H
CH3
SO3H
O
OH
O
Chemistry 3720
Chapters 19-23 Synthesis Problems
These problems are typical of those that will be on the next exams in 3720. You should be comfortable
with each reaction in the forward direction, how to think about each reaction in a retrosynthetic manner,
and then be able to complete multi-step syntheses.
1. Give the major organic product(s) from each of the following reaction sequences and then a detailed
mechanism for each reaction. Be careful with any regiochemical issues.
a.
xs CH3OH
Cl
cat. H
O
O
c.
Br
O
d
O
O
O
xs EtOH
cat. H+
cat. H+
xs CH 3OH
OCH 3
cat. H+
e.
xs CH3OH
OH
+
HOCH2CH2OH
H
b.
cat. H+
O
f.
xs MeOH
MeO
O
cat. H+
2. Give the major organic product(s) from each step of the following synthetic scheme.
1.
2.
3.
4.
CH 3COCl, AlCl3
Br2 , Fe
HOCH 2CH 2OH, cat. TsOH
Mg, ether
5. H2 C=O, ether
6. aq. NH 4 Cl (quench)
7. PCC, CH2 Cl2
8. (CH3 )2 CHLi, THF
9. aq. NH 4 Cl (quench)
10. PDC, CH 2 Cl2
11. PhMgBr, THF
12. aq. NH 4Cl (quench)
13. NaH, ether
14. PhCH 2Br, ether
15. 5% HCl, 3 h, RT
16. NaBH 4, CH 3 OH
17. HBr
18. NaOCH 3 , CH 3 OH
19. m-CPBA, CH 2Cl2
20. PhMgBr, ether
21. aq. NH 4Cl (quench)
3. In the boxes provided, give the products from each step in the following “road-map” scheme.
O
MeO
PCC
xs. MeOH
2 CH3Li
CH2Cl2
cat. H+
THF
OH
CH3Br
NaNH2
H3O+
THF
(quench)
5% HCl
PhMgBr
H 3O+
THF
THF
(quench)
13C
m-CPBA
PCC
CH2Cl2
CH 2Cl2
= 175 ppm
4. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
O
O
a.
Cl
OH
NH 2
OH
N
b.
HO
O
O
c.
Ph
O
NH 2
O
Chemistry 3720
Chapters 20-22 Synthesis Problems
These problems are from various parts of 3719 and 3720 and deal with the two main synthetic issues
studied; C-C bond formation and manipulation of functional groups.
.
1. Give the major organic product(s) from each of the following aldol reactions as well as a detailed
mechanism for each case. Be careful with any regiochemical issues.
a.
b.
O
O
NaOH
KOH
CH3OH, ∆
CH3OH, ∆
O
O
O
c.
KOH
H
O
O
NaOH
d.
H
EtOH, reflux
O
CH3OH, ∆
O
e.
f.
KOH
NaOH
EtOH, reflux
H
CH3OH, ∆
O
2. Draw all of the possible aldol condensation products formed under the following conditions.
O
O
NaOH, H 2O
+
reflux
3. Provide the reagents required to make each of the following compounds via 1,4-addition chemistry.
O
O
O
4. In the following Robinson annulation, 3 aldol products are possible; draw them and then explain
why only the one shown below is formed. Give a complete mechanism for the reaction including
important resonance structures.
O
NaOH, H 2O
O
OH
O
5. Give the major products from each step of the following reaction sequences.
a.
OH
b.
1. PCC, CH2Cl2
1. Na2Cr 2O 7, H2O
H2SO4
OH
2. CH3OH, H
2. m-CPBA, CH2Cl2
+
O
c.
1. Ph3P=CH2
1. m-CPBA, CH2Cl2
d.
2. CH3OH, cat. H+
2. H2, Pd
6. Provide complete mechanisms for the following conversions. Include all resonance structures for
any intermediates that may be formed.
O
O
NaOH
O
O
O
O
O
O
OH
CH 3OH, H+
OCH 3
7. Give structures for each of the products in the following “roadmap.”
PCC
NaOH, EtOH
Et2CuLi
CH2Cl2
reflux
THF
OH
Na2Cr2O 7
aq. NH4Cl
H2SO 4, H2O
(quench)
xs CH3OH, H+
2 PhLi
aq. NH4Cl
ether
(quench)
8. The polyether compound chauncydermolide G (shown below) was recently isolated by Triplet
Pharmaceuticals Inc. and found to have promising antibiotic properties. In order to prove the
structure unequivocally, a total synthesis beginning with the shown starting material was carried out.
Give structures for each of the products in the synthetic sequence.
O
H
OH
1. NaH, THF
2. PhCH2 Br
3. PhLi, THF
4. aq. NH4 Cl (quench)
5. PCC, CH 2Cl2
6. xs CH3 OH, cat. H +
7. H 2, Pt
8. PDC, CH 2Cl2
9. (CH 3) 2CHCH 2MgBr, ether
10. aq. NH 4Cl (quench)
11. NaH, THF
12. CH 3CH2 CH2 Br
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
5% HCl, 3 h, RT
Br2 , Fe
(CH2 OH)2 , cat. H +
2 Li, THF
H2 C=O
aq. NH 4 Cl (quench)
PCC, CH2 Cl2
Ph3P=CH2 , ether
m-CPBA, CH 2Cl2
(CH3 )2 CHMgBr, ether
aq. NH 4 Cl (quench)
PCC, CH2 Cl2
Br2 , H 2O, THF
NaOCH3 , CH3 OH
CH 3CH 2CH2 MgBr, ether
aq. NH 4 Cl (quench)
NaH, THF
CH 3Br
CH 2I2 , Zn, THF
5% HCl, 3 h, RT
LDA, THF, -78 o C
CH 3CH 2Br
, THF
PPh 3
36. dil. H 2SO 4
37. HBr
Br
OMe
O
chauncy der molide G
Chemistry 3720
Chapters 21-22 Additional Synthesis Problems
1. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
a.
O
H
O
b.
O
CO 2
O
O
HO
O
O
c.
O
d.
OH
O
O
OCH3
e.
OH
CH3OH
H
N
HO
O
CH3OH
2. Give the major organic product(s) from each step of the following synthetic sequence.
OH
1.
2.
3.
4.
Na 2Cr2 O7 , H 2SO4
xs CH 3OH, cat. H2 SO4
NaOCH 3 , CH3 OH
aq. NH 4Cl (quench)
5. NaOCH3 , THF
6. CH 3 CH 2Br
7. NaOH, aq. THF
8. dil. HCl (quench)
9. 180 oC (-CO2 )
10. LDA, THF, -78 oC
11. PhCH 2 Br
3. In the boxes provided, give the products from each step in the following “road-map” scheme. Predict
the 1H NMR spectra of each of the organic products from each step.
Br 2
Mg
Fe
ether
CO 2
HNO3
H2SO4
xs CH3OH
dil. HCl
cat. H2SO4
(quench)
2 x CH 3Li
aq. NH4Cl
THF
(quench)
Sn, HCl
NaH
THF
CH3Br
4. Give complete mechanisms, including any important resonance structures for intermediates where
applicable, that explain the bond-making and bond-breaking events, in each step of the following
conversions.
O
a.
OCH 3
H 3 CO
O
2. dilute HCl (quench)
3. NaOCH 3, THF
4. PhCH 2Br
5. NaOH, aq. THF
6. dilute HCl (quench)
7. 180 o C (-CO 2)
b.
OH
O
1. NaOCH 3, CH 3OH
1. Na2 Cr 2O 7, H2 SO4
2. xs CH3 OH, cat. HCl
3. NaOCH 3, CH 3OH
4. dilute HCl (quench)
5. NaOH, aq. THF
6. dilute HCl (quench)
Ph
O
O
OH
Chemistry 3720
Further Synthesis Problems 1
1. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
a.
OH
PPh3
HO
b.
OH
OH
Br
c.
O
HO
Cl
O
d.
OH
OH
Ph
e.
OH
OH
HO
2. Give the major organic product(s) from each step of the following synthetic scheme.
OH
1.
2.
3.
4.
PCC, CH2 Cl2
NaOH, EtOH, reflux
(CH3 )2 CuLi, ether
aq. NH 4 Cl (quench)
5.
6.
7.
8.
PhMgBr, ether
aq. NH 4 Cl (quench)
NaNH 2, THF
CH 3Br
3. In the boxes provided, give the products from each step in the following “road-map” scheme.
OH
PCC
PhMgBr
CH2Cl2
THF
aq. NH4Cl
(quench)
PCC
(CH 3)2CuLi
THF
aq. NH4Cl
CH2Cl2
(quench)
CH3Br
Br2
NaOCH3
CHCl 3
CH3OH
(CH3)2CuLi
THF
NaBH4
aq. NH4Cl
CH3OH
(quench)
4. Give complete mechanisms, including any important resonance structures for intermediates where
applicable, that explain the bond-making and bond-breaking events in the following conversions.
a.
O
1. m-CPBA, CH2 Cl2
OH
OH
2. 2 PhMgBr, THF
3. aq. NH4 Cl (quench)
O
b.
+
Ph
Ph
O
1. HNO3 , H 2SO 4
OH
o
2. LDA, THF, -78 C
3. O
Ph
4. aq. NH 4 Cl (quench)
Ph
NO 2
Chemistry 3720 Problem Set Keys Chemistry 3720
Chapters 1-19 Synthesis Problems - Key
These problems are typical of those that will be on the upcoming exams in 3720.
1. From Chapters 1-19: Show retrosynthetic analyses for each of the following molecules that go back
only to the starting materials given below. Then, using any chemistry seen in 3719 and 3720 so far,
give an efficient synthesis of each molecule showing the products formed in each step. Assume that
you have access to any of the usual reagents such as Br2, AlCl3, Fe, HBr, HNO3, H2SO4, etc.
a
.
Retrosynthesis
OH
OH
O
Li
H
Br
Synthesis
Br2, heat
Br
2 Li, ether
Li
O
H
OH
b
H 3O+
OLi
Retrosynthesis
OH
OH
Li
Br
Synthesis
Br
Br 2, Fe
2 Li, ether
Li
O
OH
OLi
+
H3O
O
c.
Retrosynthesis
OH
OH
O
H
Li
Br
Synthesis
Br
Br 2, Heat
Li
2 Li, ether
O
H
OH
OLi
H 3O +
d.
Retrosynthesis
OH
OH
O
MgBr
Br
O
Cl
Synthesis
O
OMgBr
MgBr
CH 3COCl
ether
AlCl3
H3 O+
Br
Mg
ether
OH
MgBr
e.
Retrosynthesis
OH
OH
O2 N
O
O2 N
O2 N
MgBr
O
O
Cl
Br
Synthesis
O
CH 3Cl
O
CH 3COCl
HNO3
AlCl3
H 2SO 4
O2 N
AlCl3
CH 3
Br2
Br
Mg
MgBr
ether
ether
heat
OH
BrMgO
H 3O+
O 2N
O 2N
2. From 13 and 14: Give structures of the products from each step within the following “roadmap” and
match the spectral data to the product.
O
Br 2 , heat
O
Br
Na 2Cr2 O7
Mg, ether
MgBr
OH
H 3O +
H2 SO4
H 2O
( 13 C 200 ppm)
(IR 3300 cm-1)
H
OMgBr
3. From 13-19: Give structures of the products from each step in the following reaction sequences.
a.
1. Br 2 , heat
2. 2 Li, ether
3. CH 3CHO
LiO
Li
Br
2.
1.
HO
3.
Br
4.
5.
4. H 3O +
5. HBr
b.
1. CH 3COCl, AlCl3
2. LiAlH4 , ether
3. H3 O+
O
O
Al
2.
1.
OH
3.
Li+
4. NaH, ether
5. CH 3CH2 Br
ONa
4.
O
5.
4
c.
O
1. NaBH 4, CH 3OH
2. HBr
3. 2 Li, ether
LiO
OH
Br
1.
HO
Li
2.
3.
4.
5.
4. CH3 CH 2CHO
5. H 3O+
d.
1. H 2SO 4, H2 O
2. Na2 Cr 2 O7, H2 SO4
3. PhMgBr, ether
OH
1.
Ph
O
2.
3.
4. H 3O+
5. NaH, ether
6. CH3 CH 2CH 2Br
Ph
5.
OMgBr
Ph
ONa
6.
Ph
4.
OH
O
e.
OH
1. PDC, CH 2Cl2
2. CH3 Li, ether
3. H 3O +
H
OLi
O
2.
1.
OH
3.
Ph
OMgBr
O
5.
4.
Ph
OH
6.
4. Na 2Cr 2O7 , H 2SO 4
5. PhMgBr, ether
6. H3 O+
f.
1. CH 3COCl, AlCl3
2. HNO3 , H2 SO4
3. NaBH 4, CH 3 OH
4. NaH, ether
5. CH3 CH 2 CH 2Br
O
1.
O
2.
OH
ONa
O
3.
4.
5.
NO2
NO 2
NO2
NO 2
4. From 1-19: Design syntheses of the following molecules using any of the chemistry seen so far in
3719 and 3720 and using only the sources of carbon shown below. Again, assume that you have
access to all of the common inorganic reagents (Br2, AlCl3, Fe, HBr, etc.).
a.
Design (Retrosynthesis)
O
O
HO
Cl
NH2
HO
Br
+
O
NH2
OH
OH
NO2
NH 2
HO
Li
Br
O
+
O
NO 2
NO2
OH
OH
NO2
NO2
O
O
+
Cl
Construction (Synthesis)
HBr
2 Li
HO
Br
Li
ether
O
O
O
Cl
HNO 3
AlCl3
H2 SO4
ether
O
O
Sn
ONa
OH
NaH
Br
ether
HCl
NH 2
NO2
NO 2
NO2
NO2
b.
Design (Retrosynthesis)
HO
OH
OH
HO
HO
O
HO
Br
OH
Li
OH
H
MgBr
O
Br
Construction (Synthesis)
HBr
2 Li
Br
OH
Br 2
heat
Li
ether
Br
OH
Mg
ether
PDC
O
CH 2Cl2
H
MgBr
H 3O +
PDC
ether
CH2 Cl2
O
BrMgO
H 3 O+
HO
HO
LiO
ether
c.
Design (Retrosynthesis)
O
O
OH
OCH 3
CH3 Br
Br
HO
O
O
OH
CH 3 Br
+ CH 3MgBr
H 3CO
3 o alcohol
(2 equiv. subst.)
Construction (Synthesis)
O
0.5
Mg
CH 3 Br
CH 3MgBr
ether
OMgBr
OCH3
ether
HO
H 3O+
HBr
O
Br
NaH
ONa
OH
ether
d.
Design (Retrosynthesis - several ways to do this one)
O
Br
H
H
Li
Br
O
OH
OH
OH
d. (cont’d.)
OH
Br
O
H
Li
OH
H
OH
H
O
H
Li
H
Br
Construction (Synthesis)
Br
Br
Br
Br2
Br 2
Br2
heat
heat
Fe
2 Li
ether
2 Li
Li
ether
2 Li
ether
Li
Li
O
Li
H
OLi
O
H
ether
ether
H
OLi
OH
H 3O +
PCC
H
H
CH 2Cl2
H 3 O+
Li
OH
O
PCC
CH 2Cl2
ether
OLi
H 3O +
HBr
Br
OH
e.
Design (Retrosynthesis)
OH
CH3 CH 2 OH
OH
OH
Li
Br
O
Li
Br
HO
H
OH
OH
O
Construction (Synthesis)
HO
HBr
Br
PCC
CH2Cl2
2 Li
Li
H
Br 2
2 Li
Fe
ether
H 3O +
Li
O
OLi
ether
OLi
O
ether
"steric contr ol"
(quench)
OH
dil. H 2SO4
(E1 )
OH
(quench)
dil. H 2SO4
(E1 )
Li
H 3 O+
Li
Br
ether
OH
OH
m-CPBA
CH2 Cl2
(E/Z) isomers
major product :
tetrasubstituted
(E ) isomer, alkene
conjugated with ring
Chemistry 3720
&KDSWHUVSpectroscopy Problems - Key
1. (10 pts) An unknown organic compound has the molecular formula C5H12O, in the mass spectrum, M+
= 88.09. Given the following 1H and 13C data, give the structure of the unknown and assign all of the 1H
and 13C signals.
4
1
3
2
PPM
1
0
H NMR (ppm) 1.14 (t, 3H, J = 7.2 Hz), 1.09 (d, 6H, J = 7.0 Hz), 3.19 (septet, 1H, J = 7.0 Hz),
3.50 (q, 2H, J = 7.2 Hz)
70
60
13
50
40
PPM
30
20
10
C NMR (ppm) 15.5, 22.3 (double), 64.8, 71.8
3.50 (q)
O
H 3C
H3C
H
HH
1.13 (d)
O
3.19 (sept)
1
CH 3 1.10 (t)
CH3
CH 3
22.3
64.8
O
71.8
22.3
15.5
0
2. (10 pts) Draw the approximate 13C NMR spectrum of the following molecule. Include approximate
chemical shifts and indicate which signal corresponds to which carbon(s) in the molecule.
205.5
O 127.4
104.1
29.3
H3C
O
153.6 64.9
153.6
127.4
205.5
104.1
CH 3
200
180
160
140
O
64.9
29.3
220
14.8
O
14.8
120
100
PPM
80
60
40
20
0
3. (10 pts) A chemist produces a new compound with the following spectral characteristics and considers
the new material to be one of the possibilities shown below. Which structure is correct and why?
Include a complete assignment of all of the spectral data in your answer.
1
H NMR (ppm)
13
C NMR (ppm)
IR (cm-1)
1.43 (t, 3H, J = 7.0 Hz), 3.47 (s, 3H,), 4.11 (q, 2H, J = 7.0 Hz), 4.76 (s, 2H), 7.17
(m, 2H), 7.83 (m, 2H)
14.8, 57.2, 64.6, 81.2, 126.1, 129.4 (double), 129.7 (double), 163.8, 198.3
1740, 810
O
O
OCH3
OCH 3
O
O
O
OH
O
OCH 3
OH
O
O
O
O
O
O
4.09
O
64.6
O
1.32
7.10
7.10
7.83
7.83
163.8
129.7
129.4
126.1
3.30
O
O
O
O
4.63
14.8
129.7
129.4
198.3
57.2
O
81.2
IR: 1740 = C=O, 810 = para disubstitution
2
4. (10 pts) Draw the expected 1H and 13C NMR spectra of the following molecules. Include chemical
shifts and line shapes (singlet, doublet, etc.) in the 1H spectra and intensities in the 13C spectra. Also
indicate which signal corresponds to which proton(s) and carbon(s).
a.
1.13
O
3.62
1.06
2.47
3.19
O
3.09
4
1.13
3
62.6
7.9 210.8
220
1
0
22.3
O
35.9
2
PPM
45.1
200
71.8
O
180
22.3
160
140
120
PPM
3
100
80
60
40
20
0
b.
1.19
O
1.19
3.62
1.06
2.70
3.09
O
1.19
1.06
4
3
213.6
1
0
28.2
O
60.4 73.8
17.6
41.0
2
PPM
42.9
O
28.2
28.2
17.6
220
200
180
160
140
120
PPM
4
100
80
60
40
20
0
c.
1.13
O
3.62
1.20
3.09
1.20
3.19
O
1.13
1.20
4
3
44.3
63.2
25.9
213.8
25.9
220
200
1
0
22.3
O
25.9
2
PPM
40.1
71.8
O
180
22.3
160
140
120
PPM
5
100
80
60
40
20
0
d.
O
3.62
1.06
2.70
3.50
O
3.09
1.10
1.06
4
3
213.6
2
PPM
1
0
O
65.4
17.6
41.0
42.3
66.3
O
15.2
17.6
220
200
180
160
140
120
PPM
6
100
80
60
40
20
0
5. (10 pts) An unknown organic compound has the molecular formula C11H14O2. Given the following
spectral data, provide a structure for the unknown that agrees with the data, and then assign the data.
1
H NMR (ppm)
1
H NMR data
2.50 (s, 3H), 2.75 (t, 2H, J = 7.2 Hz), 3.30 (s, 3H), 2.52 (t, 2H, J = 7.2 Hz), 7.377.76 (m, 4H)
13
C NMR (ppm)
26.6, 35.3, 59.3, 73.0, 126.0, 127.7, 128.5, 132.1, 1391, 139.2, 197.0
Mass spectrum (m/z) 178.10 (M+)
Infra Red (cm-1)
1730, 760, 690
CH 3 2.50
O
7.71
3.52
3.30
O
8
13
7.76
7.37
2.75
7.48
7
6
5
4
PPM
3
100
PPM
80
2
1
0
C NMR data
O
139.1
127.7
197.0
126.0
73.0
59.3
O
200
CH 3 26.6
35.3
139.3
132.1
180
128.5
160
140
120
60
40
(m/z) 178.10 (M+): this means that C11H14O2 is the actual formula of the unknown
Infra Red (cm-1): 1730 corresponds to C=O; 760, 690 correspond to meta substitution
7
20
0
6. (10 pts) An unknown organic compound has the molecular formula C12H16O2 and, in the mass
spectrum, M+ = 192.12. Given the following 1H and 13C data, give the structure of the unknown and
then assign all of the 1H signals.
1
H NMR (ppm)
13
1
C NMR (ppm)
1.20 (d, 6H, J = 7.0 Hz), 1.29 (t, 3H, J = 7.1 Hz), 2.87 (septet, 1H, J = 7.0 Hz),
4.30 (q, 2H, J = 7.1 Hz), 7.41 (d, 2H), 7.97 (d, 2H)
14.1, 23.3 (double), 33.2, 60.9, 126.0 (double), 127.3, 129.6 (double), 155.7,
165.9
H NMR data
1.29
O
O
4.30
7.97
7.97
7.41
7.41
2.87
1.20
9
13
8
7
1.20
6
5
PPM
4
3
2
1
0
60
40
20
0
C NMR data
14.1
O
O
60.9
127.3
129.6
126.0
152.7
165.9
129.6
126.0
33.2
23.3
180
160
140
120
100
23.3
PPM
80
M+ = 192.12 means that C12H16O2 is the actual formula of the compound
8
Chemistry 3720
Chapter 19 - Benzene Synthesis Problems - Key
Provide an efficient synthesis of each of the following substituted benzenes from benzene
itself. Use any of the reagents seen in Chemistry 3719/3720 so far and pay careful
attention to the order of steps. Assume that mixtures may be separated.
CH3
Put CH3 on f irst then send next
gr oup o/ p major and separate the
isomers
1. CH3Cl, AlCl3
2. CH3COCl, AlCl3
O
Br
1. Br2, Fe
2. CH3Cl, AlCl3
(separate from o-isomer)
3. KMnO4
Br and CH3 both o/ p dir ectors but
CH3 is acti vating - probably a cl eaner
reacti on (f ewer over-substi tuted products
if Br goes on f ir st - have to oxid ize l ast
as -CO2H i s a meta director
CO2H
NH2
Putti ng NO2 or the acyl group on
f i rst would send the next gr oup to
the meta position (ei ther would d o)
and then reduction would gi ve the
d esi red product
1. CH3CH2COCl, AlCl3
2. HNO 3, H2SO4
3. Sn, HCl
4. Zn, HCl
SO3H
Put CH3 on f irst (o/p d irector) then
bri ng i n SO3H gr oup (m d irector) oxi dize CH 3 to CO2H (m dir ector)
1. CH3Cl, AlCl3
2. SO3, H2SO 4
(separate from o-isomer)
3. KMnO 4
CO 2H
CH3
SO 3H
1. CH3Cl, AlCl3
2. SO3, H2SO4
O
OH
1. CH3Cl, AlCl3
2. CH3COCl, AlCl3
(separate from o-director)
3. KMnO4
Introduce CH3 f i rst (o/ p di rector),
separate i somers, then bring i n
SO3H gr oup (m d irector)
Put CH3 on f i rst (o/ p di rector) then
bring in acyl gr oup (m d irector) separate f rom o-isomer - then oxi dise
the CH 3 group to CO2H
O
Chemistry 3720
ChDSWHUV 1-23 Synthesis Problems Key
These problems are typical of those that will be on the next exams in 3720. You should be comfortable
with each reaction in the forward direction, how to think about each reaction in a retrosynthetic manner,
and then be able to complete multi-step syntheses.
1. Give the major organic product(s) for each of the following sets of reaction conditions and then a
detailed mechanism for each reaction. Be careful with any regiochemical issues.
a.
OCH 3
OCH 3
xs CH3OH
Cl
+
cat. H
O
OCH3
OCH3
- H+
Cl
Cl
H
ketone gives acetal
H
O
H
CH3
Cl is completely unreactive under
these conditions
CH 3
O
Cl
O
Cl
H
HOCH 3
Cl
O
H
Cl
H
O
O
CH 3
O
+
H trans.
Cl
H
H
O
HOCH 3
CH 3
-H 2O
O
CH 3
Cl
H
b.
H
O
O
H
OH
CH 3
O
xs CH3OH
- H+
O
OCH 3
cat. H+
H
OCH3
carb. acid gives ester
O
O
H
OH
H
O CH 3
O
H
O
O H
H
OCH 3
O
H
O
H+ trans.
O
OH
OH
CH3
HOCH 3
H
O
H
H
OH2
CH 3
O
-H 2O
c.
O
HOCH2CH2OH
H
O
O H
H
cat. H
O
H
- H+
O
+
H
O
O
R
H
aldehyde gives acetal
The aldehyde is much more reactive than the alkene
under these conditions so the alkene survives
H
O
OH
H
H
H
OH
HO
O
O
H
H
H+ trans.
O
H
H
H O
H
- H 2O
OH
O
H
OH
OH
O
H
d.
H
O
O
O
H
OCH3
CH 3
CH 3O
xs CH3OH
O
CH 3O
cat. H+
OCH 3
CH 3O
H
ketone gives acetal
H
O
CH 3O
- H+
OCH3
ester could also react but overall there would be
no net change (OCH3 swapped for OCH 3)
O
O
CH 3O
O
OCH3
H
O
H
O
OCH3
HOCH 3
OCH 3
O
CH3 O
H
O
H+ trans.
OCH 3
H
O
CH 3O
H
O
- H 2O
CH3O
OCH3
O
OCH 3
HOCH 3
e.
H
Br
O
R
O
H
Br EtO OEt
Br EtO OEt
H
- H+
xs EtOH
+
cat. H
ketone gives acetal
Br
O
Br
O
the bromide is completely unreactive
under these reaction conditions
H
H
Br
O
H
O
Et
H+ trans.
Br
H
H
O
Br
H
- H2O
OEt
Br EtO
HOEt
OEt
HOEt
f.
O
O
xs MeOH
MeO
MeO
cat. H+
O
O
- H+
MeO
MeO OMe
MeO OMe
H
ketone gives acetal
H
O
H
Me
O
the ester would not change overall even if
it did react under these conditions
O
MeO
MeO
O
OMe
H
HOMe
HOMe
O
MeO
O
H
O
Me
H
O
H trans.
MeO
O
O
+
Me
- H2O
MeO
O
H
O
MeO
H
O
H
O
Me
2. Give the major organic product(s) from each step of the following synthetic scheme.
1.
2.
3.
4.
CH 3COCl, AlCl3
Br2 , Fe
HOCH 2CH 2OH, cat. TsOH
Mg, ether
5. H2 C=O, ether
6. aq. NH 4 Cl (quench)
7. PCC, CH2 Cl2
8. (CH3 )2 CHLi, THF
9. aq. NH 4 Cl (quench)
10. PDC, CH 2 Cl2
11. PhMgBr, THF
12. aq. NH 4Cl (quench)
13. NaH, ether
14. PhCH 2Br, ether
15. 5% HCl, 3 h, RT
16. NaBH 4, CH 3 OH
17. HBr
18. NaOCH 3 , CH 3 OH
19. m-CPBA, CH 2Cl2
20. PhMgBr, ether
21. aq. NH 4Cl (quench)
O
O
2.
1.
O
4.
O
5.
H
OLi
O
7.
H
O
O
O
10.
O
OLi
O
H
O
11.
O
O
OH
Ph
O
O
14.
ONa
Ph
15.
OCH 2Ph
Ph
OCH2 Ph
Ph
OH
16.
Br
17.
OCH 2Ph
Ph
18.
Ph
20.
OCH 2Ph
Ph
OCH2 Ph
OCH 2Ph
Ph
OMgBr
O
19.
O
12.
O
13.
O
OH
O
OMgBr
Ph
O
OH
9.
H
O
H
O
8.
H
O
6.
H
O
O
Br
O
MgBr
O
3.
Br
O
O
Ph
Ph
OCH2 Ph
21.
OH
Ph
OCH 2Ph
Ph
3. In the boxes provided, give the products from each step in the following “road-map” scheme.
O
O
PCC
MeO
OH
MeO
CH2Cl2
ONa OMe
CH3Br
Me
OMe OMe
Me
Me
OMe O
13C
Me
THF
Me
OMe
THF
CH2Cl2
(quench)
OMe OMgBr
Me
Me
Ph
Me
OMe O
Me
THF
OLi OMe
H3O+
PhMgBr
O
2 CH3Li
OMe
OMe
Me
m-CPBA
OPh
Me
OH
OMe
MeO
cat. H+
OMe H
THF
Me
O
OMe
O
xs. MeOH
NaNH2
5% HCl
OMe
Me
Me
H
Me
Me
H 3O+
(quench)
OMe OH
PCC
Ph
CH 2Cl2
OMe
Me
Me
Ph
= 175 ppm
4. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
O
O
a.
Cl
NH 2
OH
Br
O
MgBr
NH2
OH
NH2
OH
NH 2
OH
O
NH 2
NH2
O
O
NO 2
OH
NH 2
NH 2
O
O
Cl
Synthesis
Mg
HBr
OH
Br
O
MgBr
ether
O
O
Cl
AlCl3
OH
HNO 3
NaBH 4
H2SO4
CH 3OH
NO 2
NO2
OMgBr
O
H 3PO4
m-CPBA
heat
CH 2Cl2
NO 2
O
Br
THF
NO2
NO2
ONa
NaH
O
Sn
THF
NO2
(quench)
ether
NO2
OH
aq. NH4Cl
MgBr
HCl
NO 2
NH2
OH
N
b.
HO
NH 2
OH
BrMg
O
NH 2
BrMg
OH
OH
O
Synthesis
HBr
HO
Mg
Br
BrMg
ether
OH
H3PO4
m-CPBA
heat
CH2Cl2
O
O
ether
OH
OMgBr
PCC
H3O+
CH 2Cl2
(quench)
cat. H +
NH 2
N
O
c.
Ph
O
O
O
Br
O
Ph
O
HO
OH
H
O
Ph
Ph
MgBr
Ph
OH
OH
H
H
H
Synthesis
Br
Br 2
MgBr
Mg
OMgBr
ether
ether
Fe
O
H
O
OH
NaBH4
aq. NH 4Cl
H
(quench)
CH3OH
Na2Cr 2O 7
O
cat. H+
OH
O
O
H 2SO 4
OH
H
H
Chemistry 3720
Chapters 20-22 Synthesis Problems – Key
These problems are from various parts of 3719 and 3720 and deal with the two main synthetic issues
studied; C-C bond formation and manipulation of functional groups.
1. Give the major organic product(s) from each of the following aldol reactions as well as a detailed
mechanism for each case. Be careful with any regiochemical issues.
a.
O
NaOH, CH 3OH, ∆
O
H
Intramolecular aldol is much
faster than the intermolecular
reaction, therefore a cycle is
formed. Refluxing the mixture
promotes loss of H2O in the
final step and formation of the
α,β-unsaturated product. There
are two types of α-H but loss of
the other type would lead to an
unstable 3-membered ring.
O
HO
O
O
HO
O
H
O
O
OH
CH 3O H
b.
O
KOH, CH 3OH, ∆
O
Intermolecular aldol reaction is
the only possibility here since
there isn’t a second carbonyl in
the substrate. The use of KOH
as base ensures that both some
enolate and some of the starting
ketone are present. Running
these reactions at higher temp
usually results in loss of H2O,
especially when conjugation is
possible.
H
CH 3O H
O
HO
O
HO
H
O
O
O
OH
KOH, EtOH, reflux
O
c.
O
H
H
H
H
HO
O
O
O
H
RO
H
H
H
O
H
H
HO
H OEt
O
Again, intermolecular aldol
reaction is the only possibility
here since there isn’t a second
carbonyl in the substrate. The
use of KOH as base ensures that
both some enolate and some of
the starting aldehyde are
present. Carrying out these
reactions at higher temp usually
results in elimination of H2O to
form α,β-unsaturated product.
d.
O
O
O
NaOH, CH 3OH, ∆
The intramolecular aldol is
much faster than intermolecular
reaction, therefore a cycle is
formed. There are two types of
α-H in the starting material,
however only one cyclization
leads to a stable ring. Refluxing
(boiling) the mixture promotes
loss of H2O in the final step.
H
H
HO
HO
O
O
O
O
H
H
H
H
HO
O
H OCH3
e.
O
O
O
The intramolecular aldol much
faster than the intermolecular
reaction, therefore a cycle is
formed. There are several types
of α-H in the starting material;
so several cyclization paths may
be possible. The reaction is
reversible and will yield the
most stable product, the one
shown. Refluxing the mixture
promotes loss of H2O in the
final step.
KOH, EtOH
reflux
H
HO
O
H-OEt
O
O
O
HO
H
HO
O
f.
O
H
O
NaOH, CH 3OH, ∆
O
HO
HO
CH 3 O H
O
O
O
O
H
HO
O
The intramolecular aldol much
faster than the intermolecular
reaction, therefore a cycle is
formed. Two types of α-H but
only one pathway leads to a
stable product, in this case a
five-membered ring. Refluxing
the mixture promotes loss of
H2O in the final step.
2. Draw all of the possible aldol condensation products possible in the following reaction.
O
O
O
NaOH, H 2O
O
+
reflux
B
A
C-B
C-A
NaOH
O
O
O
O
O
D-A
+
C
D
O
followed by protonation
and elimination
D-B
O
O
O
O
E
E-B
E-A
F
O
O
F-A
F-B
3. Provide the reagents required to make each of the following compounds via 1,4-addition chemistry.
O
O
O
O
O
O
CuLi
2
CuLi
2
CuLi
2
4. In the following Robinson annulation, 3 aldol products are possible; explain why only one is formed.
O
O
NaOH, H 2O
O
O
H2
H3
O
OH
H1
O
H 2O
O
O
O
O
H1
O
O
H1
H2
O
H1
O
Since there are 3 different types of α-H there are 3 different enolates possible here. The outcome
of the reaction is governed by thermodynamics (i.e. stability) since the steps are reversible,
therefore the most stable product will result. The enolate formed by removal of H1 would
generate a bicylic system (somewhat strained), the one formed by removal of H2 would only
afford a 4-membered ring (quite strained), whereas the enolate generated by removal of H3 would
give the favourable 6-membered ring shown above.
5. Give the major products from each step of the following reaction sequences.
OH
1.
1. PCC, CH2Cl2
a.
O
2.
O
O
2. m-CPBA, CH 2Cl 2
1. Na2Cr2O7, H2O
H 2SO 4
b.
OH
1.
2.
O
OH
2. CH3OH, H+
O
c.
O
OCH 3
CH 3
CH 2
1. Ph 3P=CH2
1.
2.
2. H 2, Pd
d.
1. m-CPBA, CH2Cl2
2. CH 3OH, cat. H
+
1.
O
2.
OCH 3
OH
O
6. Provide complete mechanisms for the following conversions. Include all resonance structures for
any intermediates that may be formed.
O
O
O
NaOH
O
O
enol form
OH
keto form
O
O
H-OH
O
O
O
O
H
O
O
OH
O
O
O
O
O
O
H+
O
O
CH 3OH, H
OH
+
OCH 3
- H+
O
H
OCH3
O
H
OH
OH
OCH3
O
H
O
OH
HOCH 3
H
H
OH
O CH
H
3
O
H
OH
O CH
3
7. Give structures for each of the products in the following “roadmap.”
H
PCC
OH
OH
Et 2CuLi
O
O
CH2Cl2
H
NaOH, EtOH
reflux
H
Na2Cr2O7
THF
H
O
O
H
aq. NH4Cl
OLi
(quench)
H2SO4, H 2O
xs CH3OH, H +
OCH 3
Ph Ph
2 PhLi
O
OLi
ether
Ph Ph
aq. NH4Cl
OH
(quench)
8. The polyether compound chauncydermolide G (shown below) was recently isolated by Triplet
Pharmaceuticals Inc. and found to have promising antibiotic properties. In order to prove the
structure unequivocally, a total synthesis beginning with the shown starting material was carried out.
Give structures for each of the products in the synthetic sequence.
O
1.
O
H
2.
ONa
6.
OCH 2Ph
11.
H
3.
OCH 2Ph
H 3CO OCH 3
H 3CO OCH3
OH
O
5.
4.
OCH2Ph
OCH 2Ph
7. H3CO OCH 3
12.
OH
OLi
8. H3CO OCH 3
9.
H 3CO OCH3
10.
H 3CO OCH3
OMgBr
O
H 3CO OCH3
OCH 2Ph
13.
O
OH
O
14.
Br
ONa
O
O
O
15.
16.
O
O
O
Br
17.
O
Li
O
O
OLi
H
O
19.
O
O
O
20.
O
O
CH 2
O
23.
O
O
24.
OH
H
O
O
O
O
O
O
O
O
O
ONa
32.
O
O
OMe
O
O
34.
35.
OMe
O
36.
O
OMe
O
O
O
OMe
OH
Br
OMe
OMe
O
OMe
O
37.
O
O
O
OLi
OMgBr
26.
O
O
OMe
O
O
O
O
31.
H
H
OH
O
33.
O
29.
O
O
22.
O
OMgBr
O
O
Br
O
28.
O
O
H
25.
O
27.
H
O
O
OH
O
O
H
O
O
30.
21.
O
H
O
H
O
18.
Chemistry 3720
Chapters 21-22 Additional Synthesis Problems Key
1. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
a.
Retrosynthesis
O
H
O
CO2
O
O
H
O
HO
O
O
O
X
OH
X = OH, Cl, OCOPh
Br
O
MgBr
CO 2
OH
Synthesis
Br
Br2
ether
Fe
H
NaBH4
O
CH 3OH
O
O
MgBr
Mg
CO2
O
HO
xs HO
OMgBr
O
OH
dil. HCl
(quench)
cat. H2SO 4
If the alcohol is inexpensive and readily available then the Fischer esterification works well, however if
the alcohol is expensive, it is better to convert the carboxylic acid to the acid chloride (X = Cl) using
SOCl2/pyridine or the anhydride (X = OCOPh) by heating and removing H2O. Both of these reactive
carboxylic acid derivatives require 1 equivalent of alcohol to give the ester (with pyridine as a base).
b.
Retrosynthesis
O
O
HO
O
O
O
O
HO
O
Synthesis
O
Na2Cr2O7
HO
H2SO 4
HO
heat
O
O
O
(- H 2O)
The most straightforward way to make an anhydride from a volatile (i.e. easily distillable) carboxylic acid
is to heat it up with a small amount of a mineral acid and remove the water that is formed. You could also
form the acid chloride from a portion of the carboxylic acid (using SOCl2/pyridine) and then react that
with more of the remaining carboxylic acid.
c.
Retrosynthesis
O
O
O
OH
Synthesis
OH
dil. H 2SO4
O
O
Na2Cr2O7
m-CPBA
H2SO 4
CH2Cl2
O
All of the required carbon atoms for the product are found in the given starting material, which needs to
be manipulated to introduce oxygen. The system has to be oxidized to produce the lactone (cyclic ester)
so the Baeyer-Villager oxidation is appropriate.
d.
Retrosynthesis
OH
O
O
OH
OCH 3
O
CO2 CH 3
O
OCH3
CH 3OH
CO2 H
CO2 CH3
CH3 OH
CO2 H
Synthesis
CO2H
Na2Cr2O 7
OH
OH
H2SO 4
CO2 H
xs CH3OH
CO 2CH3
cat. H 2SO4
CO2CH 3
NaOCH3
CH3OH
O
O
OCH3
e.
O
O
dil HCl
(quench)
OCH 3
Retrosynthesis
H
N
HO
O
NH
Cl
O
HO
O
CH 3OH
HO
NO2
HO
O
NH2
CH3 OH
HO
H 2C=O
Br
Li
Synthesis
CH3 OH
PCC
CH2Cl 2
H2 C=O
2 Li
Li
HNO3
H2SO 4
HO
Na2Cr2O7
HO
THF
aq. NH4Cl
LiO
NO 2
HBr
Br
HO
(quench)
H 2SO4
SOCl 2
pyridine
NH 2
Sn
O
Cl
HCl
O
pyridine
H
N
O
2. Give the major organic product(s) from each step of the following synthetic sequence.
OH
1.
2.
3.
4.
Na 2Cr2 O7 , H 2SO4
xs CH 3OH, cat. H2 SO4
NaOCH 3 , CH3 OH
aq. NH 4Cl (quench)
5. NaOCH3 , THF
6. CH 3 CH 2Br
7. NaOH, aq. THF
8. dil. HCl (quench)
9. 180 oC (-CO2 )
10. LDA, THF, -78 oC
11. PhCH 2 Br
O
1.
O
2.
OH
4.
O
3.
OCH 3
OCH3
O
H
O
O
5.
O
OCH3
6.
O
O
OCH 3
O
7.
OCH3
8.
O
O
OLi
O
ONa
O
9.
OH
10.
O
11.
Ph
O
3. In the boxes provided, give the products from each step in the following “road-map” scheme. Predict
the 1H NMR spectra of each of the organic products from each step.
Br
Br2
MgBr
Mg
Fe
ether
xs CH3OH
CO 2CH 3
CO 2
dil. HCl
CO 2H
cat. H2SO4
HNO3
H 2SO4
CO2 CH 3
(quench)
OLi
2 x CH 3Li
CO2MgBr
OH
aq. NH 4Cl
THF
(quench)
NO2
NO 2
OCH3
NO 2
OCH3
Sn, HCl
NH2
7.44
NO 2
Br
7.22
7.26
7.44
4
PPM
8.21
O
0
8
6
4
PPM
MgBr
2
7.66
O
7.79
MgBr
7.66
7.26
2
7.66
7.66
7.19
7.18
6
ONa
CH3Br
NO2
7.18
8
NaH
THF
7.79
8.21
8.21
0
O
OH12.74
7.66
8.21
7.66
8
6
PPM
4
2
0
12
10
8
6
PPM
4
2
0
7.56
7.66
8
6
PPM
8.05
O
O
7.56
4
7.93
O
7.82
0
8
6
6
Li
7.64
1.30
8.25
7.64
8.19
O
8
6
PPM
7.13
8.60
2
0
2
0
2
0
1.30
1.30
8.25
O
0
8
6
PPM
ONa
7.64
1.30
1.30
8.25
7.93
1.30
8.25
8.19
N+ O
O
4
2
0
8
O
N+ O
4
3.30
1.30
N+ O
6
PPM
4
3.30
O
6.90
3.89
OH
7.93
8.19
2
7.93
O
5.52
4
PPM
4
PPM
N+
O O-
8
O
N+
O O-
1.30
8.19
8.44
8.47
8.05
2
7.64
3.89
1.30
1.30
6.68
6.56
NH 2
5.32
8
6
4
PPM
2
0
4. Give complete mechanisms, including any important resonance structures for intermediates where
applicable, that explain the bond-making and bond-breaking events in the following conversions.
a.
O
OCH3
H3 CO
H
O
CH 3O
O
2. dilute HCl (quench)
3. NaOCH 3 , THF
4. PhCH 2 Br
5. NaOH, aq. THF
6. dilute HCl (quench)
7. 180 o C (-CO2)
OCH 3
H 3 CO
O
1. NaOCH 3 , CH3 OH
H 3CO
O
Ph
O
OCH 3
O
CH3O
O H O
O O OCH3
H3 CO
H 3 CO
contd....
H 2O H
O
O
O
O
H3 CO
H3 CO
O
O
O
O
O
O
O
O
H 3 CO
Br
CH3O
O
Ph
H
O
H3 CO
H3 CO
HO O O
H 3 CO
H3 CO
H 3 CO
Ph
Ph
O
O
H
O
O
HO
H3 CO
HO
O
O
O
H2O H
O
O
O
Ph
O
Ph
Ph
H
O
O
O
O
HO
Ph
Ph
OH
Ph
O
O
tautomerism
Ph
b.
O
1. Na2 Cr 2 O7, H2 SO4
OH
O
OH
2. xs CH3 OH, cat. HCl
3. NaOCH 3, CH 3OH
4. dilute HCl (quench)
5. NaOH, aq. THF
6. dilute HCl (quench)
O
HO Cr OH
O
Na2 Cr 2O 7 + H2 SO4
H OH 2
O
HO Cr OH
O
O
chromic acid
H
HOCH 2R
O
HO Cr OH
O
H
HO Cr OH
O
H 2O
O
HO Cr
O
H
O
HO Cr OCH 2R
O
H
O
R
H
H
HO O CH2 R
HO Cr OH
O
CH 2R
HO O
HO Cr OH 2
O
HO O CH 2R
HO Cr
O
H 2O
O
H OH 2
H
O
R
H
H
CHROH
HO O
HO Cr OH 2
H
O
R
H2 O
H
H
H
HO O CHROH
HO Cr OH
O
O
H 2O
H
O
HO Cr OH
O
H
O
OH
R
H
HO
OH
R
H
H 2O
H
O
HO Cr OCHROH
O
HO O CHROH
HO Cr
O
H 3C
R
O
H
OH
OH
CH 3OH
R
O
HO Cr
O
OH
O
R
H
H 2O
H
O
R
OH
H
O
OH
O
OH
H OCH3
H
CH 3 OH
H 3C
R
O
OH 2
OH
H
R
OH
OCH3
R
O
OCH 3
O
OCH 3
contd....
O
OCH 3
H
O
Ph
Ph
H 3CO
Ph
OCH 3
OCH 3
O
H 3CO O
Ph
O
OCH 3
Ph
O
Ph
OCH3
O
O
Ph
OCH3
Ph
O
O
O
Ph
O
O
OCH3
OCH3
Ph
H 2O H
Ph
O
O
OCH3
H Ph
Ph
Ph
CH 3O
Ph
O
Ph
H Ph
O O OCH3
H Ph
OH
OCH 3
OH
H 2O H
O
O
Ph
H Ph
O
OH
O
Ph
H Ph
O
O
OCH 3
O
Ph
H Ph
O
H
Chemistry 3720
Further Synthesis Problems 1 - Key
1. Give retrosynthetic analyses for the following molecules that go back to the given starting materials,
and then provide the synthesis in the forward direction. Assume you have access to the usual other
reagents (HBr, HNO3, NaBH4, etc.) in the lab.
a.
Retrosynthesis
OH
PPh3
HO
Ph3 P
O
Ph3 P
Br
PPh3
Br
OH
HO
Synthesis
HBr
HO
PBr3
Br
OH
PCC
ether
O
Br
Ph 3P
n-BuLi
THF
CH2Cl 2
Ph 3P
O
It would also be possible to use organometallic chemistry in this synthesis (e.g. turn one piece into a Grignard
reagent and then add to a ketone, followed by acid-catalyzed elimination), however that might not give you this
alkene as the major isomer in the elimination step. The Wittig route puts the double bond in the right place
without any complications.
1
b.
Retrosynthesis
OH
OH
OH
OH
MgBr
Br
OH
O
OH
Synthesis
OH
HBr
Br
O
MgBr
Mg
BrMgO
ether
OH
PCC
aq. NH4Cl
(quench)
O
CH 2Cl2
OH
H 3PO4
80 oC
One could also make the Grignard reagent from the cyclopentanol and the ketone from the isopropanol or even
use Wittig chemistry here. Since the product is the most highly substituted alkene anyway, both methods work.
c.
Retrosynthesis
Br
O
HO
Cl
O
OH
O
Br
O
O
O
Cl
HO
2
Synthesis
O
O
OLi
Cl
LDA
THF, -78 oC
AlCl3
HBr
HO
Br
O
Br
OH
Br
HBr
NaBH 4
CH3OH
The limitation here is the starting materials that are given; the 2-carbon alcohol limits what type of chemistry
can be applied and the only logical way really is to recognize that the alpha-carbon of the ketone may be
deprotonated to form the nucleophilic enolate.
d.
Retrosynthesis
O
OH
OH
Ph
O
O
OH
O
OH
H
Ph
Ph
Ph
OH
O
OH
Synthesis
OH
O
PCC
OH
CH2Cl2
O
PCC
H
CH2Cl2
Ph
O
NaOH, EtOH
reflux
H
Ph
O
Ph
Logical to use crossed-aldol here since the alkene is alpha to the ketone carbonyl. Heating ensures elimination.
3
e.
Retrosynthesis
OH
OH
HO
OH
O
O
O
OH
Li
Br
OH
OH
HO
O
Synthesis
OH
O
PCC
O
NaOH
EtOH, ∆
CH2Cl2
HBr
2 Li
HO
Br
Li
ether
OH
aq. NH4Cl
OLi
(quench)
Given the two alcohols here the logical first disconnection is the ethyl group, which reveals a 6-carbon fragment
that is then accessible by a simple intermolecular aldol reaction. Heating the aldol step ensures that elimination
occurs to give the required α,β-unsaturated product.
2. Give the major organic product(s) from each step of the following synthetic scheme.
OH
1.
2.
3.
4.
PCC, CH2 Cl2
NaOH, EtOH, reflux
(CH3 )2 CuLi, ether
aq. NH 4Cl (quench)
5.
6.
7.
8.
PhMgBr, ether
aq. NH 4Cl (quench)
NaNH 2, THF
CH 3Br
O
1.
2.
O
4.
7.
3.
BrMgO Ph
5.
NaO Ph
OLi
O
HO Ph
6.
CH3 O Ph
8.
4
3. In the boxes provided, give the products from each step in the following “road-map” scheme.
OH
O
PCC
OMgBr
PhMgBr
H
Ph
THF
CH2Cl2
aq. NH4Cl
(quench)
OLi
OH
O
PCC
(CH3)2CuLi
Ph
Ph
Ph
THF
aq. NH4Cl
CH2Cl2
(quench)
O
Br
Br2
O
Ph
O
NaOCH3
Ph
Ph
CHCl3
CH3OH
(CH3)2CuLi
THF
OH
OLi
O
NaBH4
Ph
Ph
CH3OH
aq. NH4Cl
Ph
(quench)
4. Give complete mechanisms, including any important resonance structures for intermediates where
applicable, that explain the bond-making and bond-breaking events in the following conversions.
a.
R O H
O
OH
1. m-CPBA, CH 2Cl2
OH
+
2. 2 PhMgBr, THF
3. aq. NH 4Cl (quench)
O
H
O
H
O
Ph
Ph
H
O
H
O
H
O
HO OCAr
OH
OH
+
Ph
H 3O +
Ph
O
O
O
Ar
OMgBr
Ph
Ph OMgBr
O
Ar
O
OMgBr
Ph
O
δ - δ+
Ph MgBr
O
H
O
δ - δ+
Ph MgBr
O
Ph
OMgBr
5
b.
O
O
1. HNO 3, H2 SO4
OH
o
2. LDA, THF, -78 C
3. O
Ph
NO2
Ph
4. aq. NH4 Cl (quench)
O
HO 3S O H
O
O
H 2O N
O
H O N
O
O
- H2O
O N O
H NO2
O
O
H2O
O
H
Ph
NO 2
NO2
O
NO 2
O
O
OLi H NH3
OH
Ph
NO2
O
N(i-Pr)2
H NO 2
O
Ph
NO2
H NO2
6
Chemistry 3720 Practice Exams and Answer Keys Practice Exam 1
Chemistry 3720
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam and you may use the attached spectroscopy sheet as needed. Good Luck.
1. (8 pts) Give the major final products from the following and explain the different regiochemical outcomes in
terms of the mechanism(s) operating.
(Klein Chapter 14)
a.
O
1. PhMgBr, ether
2. H3O+ (quench)
b.
O
CH3OH
catalytic H+
1
2. (20 pts) Give the major organic product(s), including any stereochemical issues, expected from each step in
the following reactions. You do not have to show any mechanisms.
(Klein Chapters 13 and 14)
O
a. b. c. 1. CH3MgBr, ether
2. H+ quench
3. H2, Pd
OH
1. H3PO4, heat
2. m-CPBA, CH2Cl2
3. NaOH, H2O
OH
1.
NH+ [(O Cr) O]3
2
2
2. LiAlD4, ether
3. aq. NH4Cl
d. e. O
1. NaBH4, CH3OH
H
2. NaNH2, THF
3. CH3CH2CH2Br
SH
1. NaOCH3, THF
1.
2. (CH3)2CHBr
3. xs H2O2, aq. THF
2
3. (16 pts) Give the expected major product from each step of the following reaction sequence. No need to
show any mechanisms.
(Klein Chapter 13)
4. (9 pts) Give the expected final product(s) formed in each of the following cases. (Klein Chapter 14)
a.
O
excess HBr
b.
O
excess HBr
c.
O
excess HI
3
5. (7 pts) Give the expected major product formed under the following reaction conditions, and then a detailed
mechanism for the conversion. How would you tell the product is an alcohol by IR spectroscopy?
(Klein Chapters 13-15)
6. (8 pts) A recently isolated microbial metabolite is found to have the empirical formula C4H7O and its mass
spectrum shows M+ = 142. Significant signals are seen in the IR spectrum at 1740 and 1650 cm-1. The 1H
NMR spectrum, collected in CDCl3, is given below. Provide a structure for the organic compound that
matches the data, and then match the protons in the molecule to the 1H NMR signals. (Klein Chapter 15)
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1 1
H NMR (ppm): 1.06 (d, 6H, J = 7.1 Hz), 1.36 (t, 3H, J = 7.0 Hz), 2.52 (octet, 1H, J = 7.1 Hz), 4.20 (q, 2H, J = 7.0 Hz), 5.83 (d, 1H, J = 16.0 Hz), 6.88 (dd, 1H, J = 7.1, 16.0 Hz)
4
7. (12 pts) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials as
sources of carbon. Then give a detailed synthesis of the compound that shows each product formed along
the way. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, etc.), as well
as techniques for separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.
(Klein Chapters 13-14)
O
from
O
5
and
H
8. (20 pts) Give the major organic product(s) expected from each step in the following reactions. You do not
have to show any mechanisms. (Klein Chapters 13 and 14)
O
a. b. c. 1. NaBH4, CH3OH
2. PBr3
3. NaN3, DMSO
Cl
1. Mg, ether
2. CH3CHO
3. dil. aq. NH4Cl
OH
1. H2SO4,
2. OsO4, H2O2, NaOH
3. HIO4
d. e. 1. Br2, H2O
2. NaNH2, THF
3. NaSCH3, DMF
O
1. LiAlH4, ether
2. dil. aq. NH4Cl
3. CH3COCl, pyridine
6
Chemistry 3720
Practice Exam 1 - Key
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam and you may use the attached spectroscopy sheet as needed. Good Luck.
1. (8 pts) Give the major final products from the following and explain the different regiochemical outcomes in
terms of the mechanism(s) operating.
(Klein Chapter 14)
1
2. (20 pts) Give the major organic product(s), including any stereochemical issues, expected from each step in
the following reactions. You do not have to show any mechanisms.
(Klein Chapters 13 and 14)
O
a. b. c. 1. CH3MgBr, ether
2.
1.
H3C
OH
H
H3C OH
H3C OMgBr
3.
2. H+ quench
H
3. H2, Pd
racemic
H
OH
1. H3PO4, heat
2.
1.
OH
O
3.
H
OH
2. m-CPBA, CH2Cl2
3. NaOH, H2O
meso
OH
1.
NH+ [(O Cr) O]3
2
O
D OAlR3
2.
1.
racemic
D OH
3.
2
2. LiAlD4, ether
3. aq. NH4Cl
racemic
racemic
d. e. O
1. NaBH4, CH3OH
H
OH
1.
H
2. NaNH2, THF
ONa
2.
H
H
O
3.
H
H
H
3. CH3CH2CH2Br
SNa
SH
1. NaOCH3, THF
1.
SCH(CH3)2
2.
2. (CH3)2CHBr
3. xs H2O2, aq. THF
2
SO2CH(CH3)2
3.
3. (16 pts) Give the expected major product from each step of the following reaction sequence. No need to
show any mechanisms.
(Klein Chapter 13)
4. (9 pts) Give the expected final product(s) formed in each of the following cases. (Klein Chapter 14)
a.
O
OH
excess HBr
Br
+
b.
O
excess HBr
Br
Br
c.
O
I
excess HI
I
+
3
5. (7 pts) Give the expected major product formed under the following reaction conditions, and then a detailed
mechanism for the conversion. How would you tell the product is an alcohol by IR spectroscopy?
(Klein Chapters 13-15)
The product would have a broad absorption at ~3600 cm‐1 in the IR spectrum 6. (8 pts) A recently isolated microbial metabolite is found to have the empirical formula C4H7O and its mass
spectrum shows M+ = 142. Significant signals are seen in the IR spectrum at 1740 and 1650 cm-1. The 1H
NMR spectrum, collected in CDCl3, is given below. Provide a structure for the organic compound that
matches the data, and then match the protons in the molecule to the 1H NMR signals. (Klein Chapter 15)
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1 O
5.83
H
4.20
O
1.36
1.06
2.52
H 6.88
Unsat = 8-7+1 = 2
1.06
8
7
6
5
4
PPM
1
3
2
1
H NMR (ppm): 1.06 (d, 6H, J = 7.1 Hz), 1.36 (t, 3H, J = 7.0 Hz), 2.52 (octet, 1H, J = 7.1 Hz), 4.20 (q, 2H, J = 7.0 Hz), 5.83 (d, 1H, J = 16.0 Hz), 6.88 (dd, 1H, J = 7.1, 16.0 Hz)
4
0
7. (12 pts) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials as
sources of carbon. Then give a detailed synthesis of the compound that shows each product formed along
the way. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, etc.), as well
as techniques for separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.
(Klein Chapters 13-14)
5
8. (20 pts) Give the major organic product(s) expected from each step in the following reactions. You do not
have to show any mechanisms. (Klein Chapters 13 and 14)
O
a. b. c. OH
1.
Br
2.
N3
3.
1. NaBH4, CH3OH
2. PBr3
3. NaN3, DMSO
r acemic
r acemic
r acemic
ClMgO
Cl
MgCl
1.
HO
2.
3.
1. Mg, ether
2. CH3CHO
3. dil. aq. NH4Cl
r acemic
r acemic
OH
1.
OH OH
2.
3.
O
1. H2SO4,
CHO
2. OsO4, H2O2, NaOH
3. HIO4
r acemic
d. e. 1.
Br
2.
3.
1. Br2, H2O
SCH3
O
2. NaNH2, THF
OH
3. NaSCH3, DMF
ONa
meso
r acemic
r acemic
O
O
1. LiAlH4, ether
OAlR3
1.
2.
OH
3.
O
2. dil. aq. NH4Cl
3. CH3COCl, pyridine
r acemic
6
r acemic
r acemic
Chemistry 3720
Practice Exam 2
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam and you may use the attached spectroscopy sheet as needed. Good Luck.
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1
1. (10 pts) Give the expected major product(s) from the following nitration reaction, and then give a complete
mechanism for the conversion that includes resonance structures for the intermediate(s) formed. Explain
why you only get certain isomer(s) as the major product(s) in this reaction. (Klein Chapter 19)
1
2. (8 pts) Give the structure of an unknown organic compound with the formula C7H14O2 and the following
spectral characteristics, and then match the 1H signals to your structure:
1
H NMR (CDCl3): 0.90 (t, 3H, J = 7.0 Hz), 1.14 (d, 6H, J = 6.9 Hz), 1.73 (sextet, 2H, J = 7.0 Hz), 2.67
(septet, 1H, J = 6.9 Hz), 4.13 (t, 2H, J = 7.0 Hz)
13
C NMR (CDCl3): 10.3 (q), 19.1 (q, double intensity), 21.9 (t), 34.0 (d), 66.5 (t), 177.0 (s)
(Klein Chapter 16)
3. (10 pts) Provide the expected major product(s) from the following reaction, and then give a complete
mechanism for the process that includes any important resonance structures. (Klein Chapter 19)
CO2H
Br2, FeBr3
2
4. (20 pts) Give the major organic product(s) expected from each step in the following reaction sequences.
You do not have to show any mechanisms here. (Klein Chapters 17-19)
a. b. c. 1. H2C=CHCO2Et
2. LiAlH4, ether
3. H+ (quench)
1. CH3COCl, AlCl3
2. Zn, HCl
3. Br2, heat
1. (CH3)3CCl, AlCl3
2. Br2, FeBr3
3. 2Li, ether
4. D2O
d. e. 1. SO3, H2SO4
2. Cl2, AlCl3
3. NaOH
1. (CH3)2CHCl, AlCl3
2. Br2, FeBr3
3. HNO3, H2SO4
4. NaOCH3, CH3OH
3
5. (12 pts) Provide syntheses of the compounds below, starting from benzene, that show each product formed
along the way. You have access to all of the usual reagents in the lab (e.g. HNO3, Br2, NaOH, AlCl3, etc.),
as well as techniques for separating any isomers and byproducts as needed. (Klein Chapter 19)
a. CO2H
NH2 b. HO
CH(CH3)2
6. (12 pts) Give the products from each step of the following synthetic sequence and then, on the NMR axis
given below, draw the expected 1H spectrum of the final product. (Klein Chapters 13 and 16)
4
7. (12 pts) Consider the following reaction and then answer the questions below related to the mechanism.
(Klein Chapter 17)
Draw a reaction profile (on the axes given below) that describes energy changes during the reaction.
Energy
Reaction coordinate
In the space below, draw diagrams of all transition states and reactive intermediates (including resonance
structures), and indicate where they appear on the graph above. Indicate the rate-determining step, and
label that step as unimolecular or bimolecular. Finally, explain why the major product is formed here.
5
8. (10 pts) Provide a retrosynthetic plan for the molecule shown that goes back only to the organic
compounds provided, and then show how you would build the molecule using chemistry seen in 3719 and
3720. (Klein Chapter 19)
9. (6 pts) Indicate which of the following molecules are aromatic and explain your choices based on applying
Hückels’rule. (Klein Chapter 16)
6
Chemistry 3720
Practice Exam 2 Key
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam and you may use the attached spectroscopy sheet as needed. Good Luck.
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1
1. (10 pts) Give the expected major product(s) from the following nitration reaction, and then give a complete
mechanism for the conversion that includes resonance structures for the intermediate(s) formed. Explain
why you only get certain isomer(s) as the major product(s) in this reaction. (Klein Chapter 19)
1
2. (8 pts) Give the structure of an unknown organic compound with the formula C7H14O2 and the following
spectral characteristics, and then match the 1H signals to your structure: (Klein Chapter 16)
1
H NMR (CDCl3): 0.90 (t, 3H, J = 7.0 Hz), 1.14 (d, 6H, J = 6.9 Hz), 1.73 (sextet, 2H, J = 7.0 Hz), 2.67
(septet, 1H, J = 6.9 Hz), 4.13 (t, 2H, J = 7.0 Hz)
13
C NMR (CDCl3): 10.3 (q), 19.1 (q, double intensity), 21.9 (t), 34.0 (d), 66.5 (t), 177.0 (s)
a = 0.90 (t, 3H, J = 7.0 Hz)
b = 1.73 (sextet, 2H, J = 7.0 Hz)
c = 4.13 (t, 2H, J = 7.0 Hz)
d = 1.14 (d, 6H, J = 6.9 Hz)
e = 2.67 (septet, 1H, J = 6.9 Hz)
3. (10 pts) Provide the expected major product(s) from the following reaction, and then give a complete
mechanism for the process that includes any important resonance structures. (Klein Chapter 19)
CO2H
CO2H
Br
Br
FeBr3
Br Br
FeBr3
Br Br
CO2H
H
Br
Br
FeBr3
CO2H
H
Br
2
CO2H
H
Br
Br
FeBr3
4. (20 pts) Give the major organic product(s) expected from each step in the following reaction sequences.
You do not have to show any mechanisms here. (Klein Chapters 17-19)
a. b. c. 1. H2C=CHCO2Et
2. LiAlH4, ether
3. H+ (quench)
2.
1.
EtO2C
O
3.
LiOCH2
CH3
H
H
CH3
HOCH2
H
Br
CH3
1. CH3COCl, AlCl3
1.
2.
3.
2. Zn, HCl
3. Br2, heat
C(CH3)3
C(CH3)3
C(CH3)3
C(CH3)3
1. (CH3)3CCl, AlCl3
2. Br2, FeBr3
3. 2Li, ether
4. D2O
1.
2.
3.
4.
Br
Li
SO3H
SO3Na
D
d. e. SO3H
1. SO3, H2SO4
2. Cl2, AlCl3
1.
2.
3.
Cl
3. NaOH
1. (CH3)2CHCl, AlCl3
2. Br2, FeBr3
CH(CH3)2
1.
CH(CH3)2
2.
3. HNO3, H2SO4
4. NaOCH3, CH3OH
Cl
CH(CH3)2
3.
4.
NO2
Br
3
CH(CH3)2
Br
NO2
OCH3
5. (12 pts) Provide syntheses of the compounds below, starting from benzene, that show each product formed
along the way. You have access to all of the usual reagents in the lab (e.g. HNO3, Br2, NaOH, AlCl3, etc.),
as well as techniques for separating any isomers and byproducts as needed. (Klein Chapter 19)
6. (12 pts) Give the products from each step of the following synthetic sequence and then, on the NMR axis
given below, draw the expected 1H spectrum of the final product. (Klein Chapters 13 and 16)
4
7. (12 pts) Consider the following reaction and then answer the questions below related to the mechanism.
(Klein Chapter 17)
Draw a reaction profile (on the axes given below) that describes energy changes during the reaction.
In the space below, draw diagrams of all transition states and reactive intermediates (including resonance
structures), and indicate where they appear on the graph above. Indicate the rate-determining step, and
label that step as unimolecular or bimolecular. Finally, explain why the major product is formed here.
H
+
Br
-
H
H
+
first step T.S.
intermediate
Br
+
H
H
+
Br
second step T.S.
-
First step is R.D.S. and it is bimolecular (diene and HBr are involved); major product is the thermodynamic outcome since reaction is reversible at higher temperatures and more substituted alkene is favoured. 5
8.
(8 pts) Provide a retrosynthetic plan for the molecule shown that goes back only to the organic compounds
provided, and then show how you would build the molecule using chemistry seen in 3719 and 3720. (Klein
Chapter 19)
O
OH
?
OH
H
and
Retr osynthesis
OH
O
H
Br
Li
Synthesis
OH
OLi
OH
HBr
Br
2 Li
Li PhCHO
OH
NH4Cl
ether
ether
9. (6 pts) Indicate which of the following molecules are aromatic and explain your choices based on applying
Hückels’rule. (Klein Chapter 16)
1 = No
N
O
2 = Yes
3 = Yes
For 1 : 8 pi electrons so 4n+2 = 8 ; n = 3/2 ; not lat, not aromatic
For 2 : 6 pi electrons so 4n+2 = 8 ; n = 1 ; flat and aromatic
For 3 : 6 pi electrons so 4n+2 = 8 ; n = 1 ; flat and aromatic
6
Chemistry 3720
Practice Exam 3
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam. Good Luck.
1. (8 pts) Provide a complete mechanism, including all important resonance structures, for the following:
(Klein Chapter 22)
1
2. (20 pts) Give the major organic product(s), including any stereochemical issues, expected from each step in
the following reactions. You do not have to show any mechanisms. (Klein Chapters 20-22)
O
a. b. c. d. e. OH
1. xs CH3OH, cat. H+
2. Sn, HCl
NO2
OH
1. PCC, CH2Cl2
2. xs NaOH, xs I2
O
OH
1. SOCl2, pyridine
2. HNEt2, pyridine
O
H
1. Ph3P=CH2, THF
2. H2, Pd
O
1. LDA, THF
2. CH3CH2CH2Br
2
3. (14 pts) Provide the major organic product from each step of the following synthetic sequence (in the boxes
provided). The spectroscopic clues along the way might help. (Klein Chapters 13-22)
O
(CH3)2CuLi
H3O+
THF
(quench)
H
IR : 1700 cm-1
CH3MgBr
THF
Na2Cr2O7
H3O+
H2SO4
(quench)
IR : 1700 cm-1
IR : 3200 cm-1
PhMgBr
THF
Final product:
H3O+
Molecular formula = C11H16O
IR : 1700 cm-1
(quench)
4. (6 pts) Number the following compounds in order of their decreasing reactivity with nucleophiles; 1 = most
reactive, 3 = least reactive. Then explain your reasoning. (Klein Chapter 21)
3
5. (8 pts) Provide a complete mechanism that describes the following conversion. Include all resonance
structures for any intermediates that are formed. (Klein Chapter 21)
6. (8 pts) Provide a complete mechanism for the following annulation that includes any important resonance
structures along the way. (Klein Chapter 22)
4
7. (8 pts) Provide a retrosynthetic analysis for the following molecule that leads back only to 1-propanol as the
source of carbon. Then show an actual synthesis in the forward direction. (Klein Chapters 13-22)
8. (8 pts) Provide a complete mechanism for the following ester saponification sequence: (Klein Chapter 21)
O
O
O
i. KOH, EtOH,
ii. dilute aq. HCl
5
OH +
HO
9. (20 pts) Give the major organic product(s) expected from each step in the following reactions. You do not
have to show any mechanisms. (Klein Chapters 20-22)
O
a. b. c. 1. Br2 in H2O
2. NaCN in DMF
O
1. PhMgBr, THF
2. dilute HCl (quench)
O
O
2. dilute HCl (quench)
d. e. 1. 2 CH3MgBr, THF
O
1. NH2NH2, cat. H+
2. KOH, heat
O
1. excess NaOD/D2O
2. NaBD4, CH3OD
6
Practice Exam 3 - Key
Chemistry 3720
Name:
This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to
complete the exam. Good Luck.
1. (8 pts) Provide a complete mechanism, including all important resonance structures, for the following:
(Klein Chapter 22)
O
O
1. NaOEt, EtOH
OEt
O
OEt
H
H OEt
2. H+ (quench)
O
O
O
H+
O
OEt
O
OEt
O
O
OEt
OEt
O
O
OEt
O
O
OEt
O
OEt
O
O
O
O OEt
O
O
H OEt
OEt
O
OEt
O
O
Dieckmann Cyclization
1
OEt
O
O
O
2. (20 pts) Give the major organic product(s), including any stereochemical issues, expected from each step in
the following reactions. You do not have to show any mechanisms. (Klein Chapters 20-22)
O
a. b. c. d. e. O
O
OH
1. xs CH3OH, cat. H+
1.
OCH3
2.
OCH3
2. Sn, HCl
NO2
NH2
NO2
OH
O
1. PCC, CH2Cl2
O
1.
2.
ONa
2. xs NaOH, xs I2
+ CHI3
O
O
O
OH
1. SOCl2, pyridine
1.
Cl
2.
NEt2
2. HNEt2, pyridine
CH2
O
H
1. Ph3P=CH2, THF
1.
H
CH2CH3
2.
2. H2, Pd
OLi
O
1. LDA, THF
1.
O
2.
2. CH3CH2CH2Br
NO2
2
NH2
3. (14 pts) Provide the major organic product from each step of the following synthetic sequence (in the boxes
provided). The spectroscopic clues along the way might help. (Klein Chapters 13-22)
O
(CH3)2CuLi
H
THF
H3O+
OLi
O
(quench)
H
H
IR : 1700 cm-1
CH3MgBr
THF
Na2Cr2O7
O
H2SO4
CH3
IR : 1700 cm-1
H3O+
OH
OMgBr
(quench)
CH3
CH3
IR : 3200 cm-1
PhMgBr
THF
Final product:
H3O+
OMgBr
(quench)
H3C Ph
OH
Molecular formula = C11H16O
IR : 1700 cm-1
H3C Ph
4. (6 pts) Number the following compounds in order of their decreasing reactivity with nucleophiles; 1 = most
reactive, 3 = least reactive. Then explain your reasoning. (Klein Chapter 21)
O
OCH3
2
O
O
Cl
NHCH3
3
1
The acid chloride is the most reactive since it is least stabilized by resonance
from the leaving group; Cl is unable to delocalize a lone pair as well as O or N
due to its larger size. Cl is also a much better leaving group than O or N. The
ester is next most reactive since it is not as stabilized as the amide (O is more
electronegative and holds it lone pair tighter), additionally the O leaving group
is better than the N leaving group, again due to O being more electronegative.
3
5. (8 pts) Provide a complete mechanism that describes the following conversion. Include all resonance
structures for any intermediates that are formed. (Klein Chapter 21)
O
1. CH3MgBr, ether
C N:
CH3
2. aq. HCl (quench)
3. H2SO4, H2O,
- H+
CH3MgBr
H+
NMgBr
O
H
OH
CH3
CH3
CH3
H3N OH
CH3
H + tr ansf er
H+
NH2
NH
NH2
CH3
CH3
CH3
H2N OH2
OH2
CH3
6. (8 pts) Provide a complete mechanism for the following annulation that includes any important resonance
structures along the way. (Klein Chapter 22)
Cl
Cl
H
KOH, EtOH,
H
H3CO
CH3O
O H O
O
H3CO
CH3O
O
O
HO
R1
R1
R1
R1
H
R2
O
H
R2
O
O
R2
O
O
H
HO
H
R2
O
O
R1
R1
H
R2
O
O
O
O
RO H
Michael/Robinson sequence
4
H
R2
O
O
O
R2
HO
O
O
R1
H
H
O
O
7. (8 pts) Provide a retrosynthetic analysis for the following molecule that leads back only to 1-propanol as the
source of carbon. Then show an actual synthesis in the forward direction. (Klein Chapters 13-22)
O
H
F.G.I.
O
Retrosynthesis:
OH
O
H
O
OH
H
H
F.G.I.
F.G.I.
O
F.G.I.
HO
HO
H
Synthesis:
HO
O
PCC
CH2Cl2
O
NaOH
H
H2O,
aldol
pr oduct
H
8. (8 pts) Provide a complete mechanism for the following ester saponification sequence: (Klein Chapter 21)
O
O
i. KOH, EtOH,
O
OH +
ii. dilute aq. HCl
HO
HO
H+
O
O
O
OH
O
O
O
HO
O
O H
O
Saponification
5
9. (20 pts) Give the major organic product(s) expected from each step in the following reactions. You do not
have to show any mechanisms. (Klein Chapters 20-22)
a. b. c. O
1. Br2 in H2O
Br
2.
O
CN
2. NaCN in DMF
HO Ph
BrMgO Ph
O
1. PhMgBr, THF
1.
2.
2. dilute HCl (quench)
O
BrMgO
O
1. 2 CH3MgBr, THF
CH3
CH3
1.
2. dilute HCl (quench)
d. e. O
1.
HO
2.
OH
OMgBr
H H
NNH2
O
1. NH2NH2, cat. H+
CH3
CH3
1.
2.
2. KOH, heat
O
O
1. excess NaOD/D2O
1.
D
D
2. NaD4, CH3OH
6
2.
HO D
D
D
Chemistry 3720 Practice Exams Chemistry 3720
PRACTICE EXAM QUESTIONS
(12 pts) An unknown natural product has the formula C11H12O2 and its mass spectrum shows M+ = 176.
Important signals are seen in the IR spectrum at 1740, 760, and 690 cm-1. The compound dissolves in
CDCl3 for the NMR spectra shown below. Give a structure for the organic compound that matches the
data and then try to match the protons in the molecule to the 1H NMR signals.
1
H NMR (ppm): 2.05 (d, 3H, J = 7.0 Hz), 3.89 (s, 3H), 5.63 (dq, 1H, J = 12.0, 7.0 Hz),
6.35 (d, 1H, J = 12.0 Hz), 7.35 (m, 2H), 7.81 (d, 1H), 7.93 (d, 1H)
13
C NMR (ppm): 12.8 (q), 51.5 (q), 124.4 (d), 127.3 (d), 128.5 (d), 129.1 (d),
130.5 (d), 131.1 (s), 132.8 (d), 137.9 (s), 165.9 (s)
3720 Exam 1 2013
(Chapter 16 in Klein)
(8 pts) Each of the following molecules shows only one signal in its 1H NMR spectrum. Draw the
structure of each compound based on its chemical shift and unsaturation number.
3720 Exam 1 2013
(Chapter 16 in Klein)
(8 pts) Explain in detail the vastly different equilibrium constants for the hydration processes shown in
the equations below.
3720 Exam 2 2013
(Chapter 20 in Klein)
(14 pts) Provide the major organic product from each step of the following synthetic sequence (in the
boxes provided). The spectroscopic clues along the way might help.
O
Cl
NaBH4
AlCl3
CH3OH
IR : 1700 cm-1
H3PO4,
PhMgBr
m-CPBA
ether
CH2Cl2
then H+ quench
IR : 3400 cm
-1
Na2Cr2O7
H2SO4
xs. CH3OH
cat. H+
13
C NMR : 200 ppm
3720 Exam 2 2013
Final product:
Molecular formula = C16H18O2
Carbon NMR: 11 13C signals
(Chapters 13-16 in Klein)
(8 pts) Provide a complete mechanism for the following acetal synthesis that includes any important
resonance structures along the way.
3720 Exam 2 2013
(Chapter 20 in Klein)
(14 pts) Provide a retrosynthetic analysis for each of the following molecules that leads back only to the
sources of carbon shown in the box below. Then show an actual synthesis in the forward direction for
each.
a. b. 3720 Exam 2 2013
(Chapters 13-20 in Klein)
(9 pts) Give the expected major product(s) under the following conditions, and then give a brief mechanistic
explanation for your choice. The use of pertinent resonance structures will help in your answer.
OH
O P OH
HNO3, H2SO4
3720 Exam 1 2011
(Chapter 19 in Klein)
(8 pts) The four isomeric compounds shown below are very closely related pharmaceuticals that have
quite similar NMR, MS, UV, and IR properties. Indicate which molecule matches the 13C spectrum
below and explain why you chose that molecule. There will be no credit for simply guessing a
compound.
3720 Exam 1 2011
(Chapter 16 in Klein)
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
1. Br2, FeBr3
2. Mg, ether
a. b. c. d. e. 3. H2C=O
4. H3O+
1. (CH3)2CHCl, AlCl3
2. CH3COCl, AlCl3
3. KMnO4, heat
4. NaOH
1. HNO3, H2SO4
2. Sn, HCl
3. Cl2, FeCl3
1. CH3CH2Cl, AlCl3
2. Br2, heat
3. NaOCH3, heat
4. D2, Pt
1. CH3COCl, AlCl3
2. SO3, H2SO4
3. Zn, HCl
4. NaOCH2CH3
3720 Exam 1 2011
(Chapter 19 in Klein)
(12 pts) A newly produced organic pharmaceutical compound is found to have the formula C13H15NO2
and its mass spectrum shows M+ = 217. Significant signals are seen in the IR spectrum at 2250, 1730,
800, and 720 cm-1. The compound is soluble in organic solvents such as ethyl acetate, acetone, as well as
CDCl3 with the NMR spectra below being taken in the latter. Provide a structure for the organic
compound that matches the data, and then match the protons in the molecule to the 1H NMR signals.
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1 9
8
7
6
5
PPM
4
3
2
1
1
0
H NMR (ppm): 1.13 (d, 6H, J = 6.9 Hz), 2.72 (t, 2H, J = 7.0 Hz), 3.19 (septet, 1H, J = 6.9 Hz), 3.53 (t, 2H, J = 7.0 Hz), 7.71 (t, 1H, J = 6.5 Hz), 8.10 (d, 1H, J = 6.5 Hz), 8.25 (d, 1H, J = 6.5 Hz), 8.42 (s, 1H) 13
C NMR (ppm): 22.3 (double), 41.3, 63.1, 75.5, 112.5, 118.6, 129.3, 132.0, 133.1, 136.6, 137.4, 198.1 3720 Exam 1 2011
(Chapter 16 in Klein)
(12 pts) Give the expected major product(s) from the following acylation reaction, and then a complete
mechanism for the conversion that includes resonance structures for the intermediate formed.
3720 Exam 1 2011
(Chapter 19 in Klein)
(15 pts) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials
as sources of carbon. Then give a detailed synthesis of the compound that shows each product formed
along the way. You have access to all of the usual reagents in the lab, as well as techniques for
separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.
OH
O
O
from
Cl
H
OH
NH2
3720 Exam 1 2011
(Chapters 13-19 in Klein)
(12 pts) Provide the products from each step of the following synthetic scheme and then, on the NMR
axis given below, draw the expected 1H spectrum of the final product.
1. (CH3)3CCl, AlCl3
O
2.
Cl
, AlCl3
3. NH2NH2, KOH,
4. Br2, heat
5. 2 Li, ether
6. D2O
3720 Exam 1 2011
(Chapters 13-19 in Klein)
(10 pts) Give the expected major product formed under the following reaction conditions, and then give
a detailed mechanism for the conversion. (Hint – the major organic product has the formula C10H18O).
3720 Exam 2 2011
(Chapters 13-14 in Klein)
(10 pts) In the boxes provided, give the expected major product from each step of the following reaction
sequence. The spectroscopic clues might help you work out structures.
Br2
Cl
FeBr3
AlCl3
13
C = 6 signals
1. Mg, ether
2. D2O
KMnO4, heat
excess CH3OH
cat. H+
1
H = 3 signals
3720 Exam 2 2011
IR = 3400, 1750 cm-1
(Chapters 13-21 in Klein)
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
O
a. b. c. 3. NaOCH3, CH3OH,
4. OsO4, NaOH, H2O2
1. m-CPBA, CH2Cl2
2. PhMgBr, ether
3. H3O+ (quench)
4. PCC, CH2Cl2
CH2OH
1. Na2Cr2O7, H2SO4
2. xs CH3OH, cat. H+
3. 2 eq. PhMgBr, ether
4. H3O+ (quench)
d. e. 1. NaBH4, CH3OH
2. HBr
1. CH3COCl, AlCl3
2. NaBD4, CH3OH
3. NaH, ether
4. CH3CH2CH2CH2Br
O
1. LiAlH4, ether
2. H3O+ (quench)
3. H3PO4, heat
4. Zn, CH2I2, ether
3720 Exam 2 2011
(Chapters 13-19 in Klein)
(8 pts) Explain the vastly different equilibrium constants observed for the following two hydration
processes.
3720 Exam 3 2011 (Chapter 20 in Klein)
(10 pts) In the boxes provided, give the expected major product from each step of the following
synthetic scheme. The spectroscopic clues might help you work out structures.
KOH, EtOH
O
H
(CH3)2CuLi
reflux
THF
1
H singlet 9 ppm
H3O+ (quench)
m.p. = 200 oC
3720 Exam 3 2011
NaOH
Na2Cr2O7
aq. EtOH
H2SO4
IR = 1750 cm-1
IR = 3400, 1750 cm-1
(Chapter 22 in Klein)
(9 pts) Provide a detailed mechanism, including resonance structures where appropriate, for the
following Baeyer-Villager reaction and then explain the regiochemical outcome.
3720 Exam 3 2011
(Chapter 20 in Klein)
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
OH
a. b. c. 1. PCC, CH2Cl2
2. Br2, FeBr3
3. LDA, THF, -78 oC
4. CH2=CHCH2Br
1. Br2, low temp.
2. NaOCH3, CH3OH
O
3. Ph2CuLi, THF
4. H3O+ (quench)
CH3
1. Na2Cr2O7, H2SO4
2. xs CH3OH, cat. H+
3. HNO3, H2SO4
4. Sn, HCl
O
d. e. Br
1. xs CH3OH, cat. H+
2. Mg, ether
3. H2C=O, ether
4. H3O+ (quench)
O
H
1. PhMgBr, ether
2. H3O+ (quench)
3. PCC, CH2Cl2
4. Ph3P=CH2, ether
3720 Exam 3 2011
(Chapters 13-22 in Klein)
(9 pts) Provide a synthesis of the molecule below that uses only the given starting materials as sources of
carbon. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, PPh3, CuI,
etc.), as well as techniques for separating isomers (i.e. distillation, chromatography, etc.) as needed. No
need to show a retrosynthesis unless it helps.
3720 Exam 3 2011
(Chapters 13-23 in Klein)
(9 pts) Give a detailed mechanism for the following conversion that includes important resonance
structures for intermediates that are formed.
3720 Exam 3 2011
(Chapter 22 in Klein)
(9 pts) Give the expected major product formed under the following reaction conditions, and then give a
detailed mechanism for the synthetic sequence that includes important resonance structures for
intermediates.
3720 Exam 3 2011
(Chapter 20 in Klein)
(12 pts) Give the expected major product from each step of the following reaction sequence. No need to
show any mechanisms.
1. PCC, CH2Cl2
2. LDA, THF, -78 oC
OH
3. CH3CH2CH2Br
4. NaBH4, CH3OH
5. NaH, THF
6. CH3CH2CH2Br
3720 Exam 3 2011
(Chapters 13-22 in Klein)
(8 pts) Provide a complete mechanism for the following conversion that includes resonance structures
for intermediates that are formed.
3720 Exam 3 2011
(Chapter 22 in Klein)
(6 pts) The following sequence fails to give the product shown; explain why and then give a modified
procedure (showing all intermediate products) that results in the formation of the desired compound.
3720 Exam 3 2011
(Chapter 20 in Klein)
(6 pts) The following spectral data belong to one of the five compounds shown below; circle the correct
structure and match the 1H NMR data to that molecule.
1
H NMR (ppm): 2.34 (s, 3H), 3.30 (s, 3H), 4.80 (s, 2H), 7.16-7.48 (m, 4H)
C NMR (ppm): 21.6, 58.9, 74.8, 124.4, 128.1, 128.5, 129.3, 138.3, 138.7
760, 700
IR (cm-1):
13
3720 Exam 1 2009
(Chapter 16 in Klein)
(12 pts) An unknown organic compound has the formula C6H12O2 from mass spectrometry data and the
following signals in the 1H and 13C spectra. Give a structure for the unknown compound that agrees with
the NMR data and then match the 1H NMR signals to the protons in your answer.
1
H NMR (ppm):
13
C NMR (ppm):
3720 Exam 1 2009
1.13 (d, 6H, J = 6.9 Hz), 2.57 (q, 2H, J = 7.0 Hz), 3.19 (septet, 1H, J = 6.9
Hz), 3.67 (t, 2H, J = 7.0 Hz), 9.72 (t, 1H, J = 7.0 Hz)
22.3 (double intensity), 43.5, 61.2, 75.5, 202.2
(Chapter 16 in Klein)
(12 pts) In the lab you have a bottle of benzene and all of the usual reagents and catalysts required to do
organic synthesis. Beginning with benzene, provide an efficient synthesis of the following compounds
by using any of the reactions and reagents seen thus far in Chemistry 3719 and 3720. Show the organic
product(s) from each step of your syntheses; you may assume that isomer mixtures are separable.
NH2
CO2H
HO3S
3720 Exam 1 2009
(Chapter 19 in Klein)
(20 pts) Give mechanistic explanations for the formation of the products and the regiochemical
outcomes in the following reactions (i.e. draw the mechanisms and use resonance structures to explain
the products).
3720 Exam 1 2009
(Chapter 19 in Klein)
(8 pts) Give a detailed mechanism (including resonance structures for the intermediate) for the formation
of the product in the following reaction.
3720 Exam 1 2009
(Chapter 19 in Klein)
(9 pts) Give the major product formed under the following conditions and then a complete mechanism
for its formation. How many signals do you expect to see in the 13C NMR spectrum of the product?
3720 Exam 2 2009
(Chapter 14 in Klein)
(10 pts) On the axis given below, draw the approximate 1H NMR spectrum for the following molecule.
Label which signals belong to which protons.
3720 Exam 1 2009
(Chapter 16 in Klein)
(10 pts) Give the major products from each step of the following reaction sequence. What will the
upfield region of the 1H NMR spectrum of the final product look like (signal shapes and integration
values)?
Exam 2 2009 (Chapter 13 in Klein)
(16 pts) Give the products A through H from the following sequence. The molecular formula data and
the spectral information might help as clues.
2 Li
Br2, FeBr3
ether
A = C6H5Br
B = C6H5Li
H
O
Na2Cr2O7
H3O+
H2SO4
(quench)
E IR = 1720 cm-1
D IR = 3200 cm-1
C = C10H13LiO
CH3CH2MgBr, THF
then aq. NH4Cl
F IR = 3200 cm-1
3720 Exam 2 2009
NaNH2
CH3CH2Br
THF
THF
G C12H17NaO
(Chapter 13-19 in Klein)
H 11 signals in 13C
(9 pts) Provide the major organic product, as well as a complete mechanism for its formation, for the
following reaction. How many signals do you expect to see in the 1H NMR spectrum of the product?
3720 Exam 2 2009
(Chapter 14 in Klein)
(18 pts) Provide a retrosynthesis for each of the following target compounds that goes back to the given
starting materials the sources of carbon. Then give step-by-step syntheses of the target compounds,
showing products from each step along the way.
a.
b.
from
and
HO
O
3720 Exam 2 2009
(Chapters 13-14 in Klein)
(18 pts) Provide mechanisms for both of the following transformations that include all intermediates and
any important resonance structures.
a.
b.
3720 Exam 2 2009
(Chapters 13 and 21 in Klein)
(20 pts) Give the major organic products from each step of the following reaction sequences (i.e. when
there is more than one step, a product from each is expected).
a.
b.
c.
d.
e.
3720 Exam 2 2009
(Chapters 13-14 in Klein)
(10 pts) Give a complete mechanism for the following transformation that includes any important
resonance structures for intermediates that may be formed.
3720 Exam 2 2009
(Chapter 20 in Klein)
(9 pts) Give a complete mechanism for the formation of the product in the following transformation that
includes resonance structures where applicable. What role do you think the MgSO4 is playing here?
3720 Exam 2 2009
(Chapter 21 in Klein)
(9 pts) Provide a complete mechanism for the formation of the product in the following reaction. How
many signals do you expect to see in the 13C NMR spectrum of the product?
O
O
KOH, ethanol
O
3720 Exam 2 2009
reflux
(Chapter 22 in Klein)
(10 pts) Provide a step-by-step synthesis, showing products from each step along the way, of the
following target compound using only the given starting materials as the sources of carbon. Although
you do not have to show a retrosynthesis, using this technique might help you to solve the problem.
3720 Exam 2 2009
(Chapter 22 in Klein)
(20 pts) Give the major organic products from each step of the following reaction sequences (i.e. when
there is more than one step, a product from each is expected).
a.
b.
c.
d.
e.
O
1. LDA, THF
2. CH3CH2CH3Br
3720 Exam 2 2009 (Chapters 22-23 in Klein)
(16 pts) Give the products A through H from the following sequence. The molecular formula data and
the spectral information might help as clues.
O
Br2
Cl
FeBr3
AlCl3
A 13C NMR 200 ppm
B = C9H9BrO
1. LDA, THF
2. CH3CH2Br
Mg
(CH2OH2)
THF
cat. H+
C IR = 1720 cm-1
D = C13H17BrO2
E = C13H17BrMgO2
CO2
then H+ quench
SOCl2
dilute HCl
then CH3OH
pyridine
F 13C NMR = 175 ppm
3720 Exam 2 2009
G = C15H20O4
(Chapters 13-23 in Klein)
H = C13H16O3
(8 pts) Provide a major product from each step of the following reaction sequence.
3720 Exam 2 2009
(Chapter 22 in Klein)
(9 pts) Order the following compounds in terms of their relative reactivity with nucleophiles (1 = most
reactive, 3 = least reactive) and then give a brief explanation for your choices.
O
OCH3
O
Cl
O
NHCH3
3720 Exam 2 2009
(Chapter 21 in Klein)
(9 pts) Order the following compounds in terms of their relative boiling points (1 = highest, 3 = lowest)
and then give a brief explanation for your choices.
3720 Exam 2 2009
(Chapter 21 in Klein)
Chemistry 3720
PRACTICE EXAM QUESTIONS KEY
(12 pts) An unknown natural product has the formula C11H12O2 and its mass spectrum shows M+ = 176.
Important signals are seen in the IR spectrum at 1740, 760, and 690 cm-1. The compound dissolves in
CDCl3 for the NMR spectra shown below. Give a structure for the organic compound that matches the
data and then try to match the protons in the molecule to the 1H NMR signals.
1
H NMR (ppm): 2.05 (d, 3H, J = 7.0 Hz), 3.89 (s, 3H), 5.63 (dq, 1H, J = 12.0, 7.0 Hz),
6.35 (d, 1H, J = 12.0 Hz), 7.35 (m, 2H), 7.81 (d, 1H), 7.93 (d, 1H)
13
C NMR (ppm): 12.8 (q), 51.5 (q), 124.4 (d), 127.3 (d), 128.5 (d), 129.1 (d),
130.5 (d), 131.1 (s), 132.8 (d), 137.9 (s), 165.9 (s)
O
B
OCH3
A
CH3
E
H
D
H
C
[A 2.05 (d, 3H, J = 7.0 Hz)], [B 3.89 (s, 3H)], [C 5.63 (dq, 1H, J = 12.0, 7.0 Hz)],
[D 6.35 (d, 1H, J = 12.0 Hz)], [E 7.35 (m, 2H), 7.81 (d, 1H), 7.93 (d, 1H)] 3720 Exam 1 2013
(Chapter 16 in Klein)
(8 pts) Each of the following molecules shows only one signal in its 1H NMR spectrum. Draw the
structure of each compound based on its chemical shift and unsaturation number.
C8H8 5.8 ppm
C8H18 0.9 ppm
a.
b.
H
H3C
H3C
H3C
CH3
CH3
CH3
H
H
H
H
H
C2H4Cl2 3.7 ppm
c.
d.
H
H
C12H18 2.2 ppm
CH3
Cl
H
Cl
Cl
H
Cl
H3C
CH3
H3C
CH3
CH3
3720 Exam 1 2013
(Chapter 16 in Klein)
(8 pts) Explain in detail the vastly different equilibrium constants for the hydration processes shown in
the equations below.
O
F3C
K = 22,000
CF3
O
HO OH
F3C
CF3
H3C
K = 0.0014
CH3
HO OH
H3C
CH3
Considering the left hand side of each equation, the ketone on the left is a lot less
stable than the one on the right because the CF3 groups are powerfully electronwithdrawing whereas the CH3 groups on the right are lectron-dontating, which
serves to stabilize the electron-poor carbonyl group. Both acetals will suffer from
steric compression in which the large alkyl groups will repel, however the overall
equilibrium constant is a balance between the stabilities of the species on either side
of the equation i.e. the ketone and the hydrate. In the left equation the ketone is
significantly destabilized, in the right the ketone is favoured.
3720 Exam 2 2013
(Chapter 20 in Klein)
(14 pts) Provide the major organic product from each step of the following synthetic sequence (in the
boxes provided). The spectroscopic clues along the way might help.
O
O
Cl
OH
NaBH4
AlCl3
H
CH3OH
IR : 1700 cm-1
H3PO4,
H OH
H
PhMgBr
O
ether
H
H
H
m-CPBA
H
CH2Cl2
H
then H+ quench
IR : 3400 cm-1
Na2Cr2O7
H2SO4
O
H3CO OCH3
xs. CH3OH
cat. H+
13
C NMR : 200 ppm
3720 Exam 2 2013
Final product:
Molecular formula = C16H18O2
Carbon NMR: 11 13C signals
(Chapters 13-16 in Klein)
(8 pts) Provide a complete mechanism for the following acetal synthesis that includes any important
resonance structures along the way.
3720 Exam 2 2013
(Chapter 20 in Klein)
(14 pts) Provide a retrosynthetic analysis for each of the following molecules that leads back only to the
sources of carbon shown in the box below. Then show an actual synthesis in the forward direction for
each.
OH
Cl
a.
BrMg
OH
C-C
FGI
O
FGI
HO
Br
H
Synthesis:
Br
Br2,
BrMg
Mg
ether
O
PCC
HO
Cl
H
CH2Cl2
OH
SOCl2
OMgBr
NH4Cl
OH
OH
b.
O
C-C
FGI
H
FGI
Br
FGI
Li
FGI
HO
Synthesis:
Br
Br2
Li
ether
FeBr3
O
PCC
HO
2 Li
H
CH2Cl2
H3PO4
OH
NH4Cl
OLi
3720 Exam 2 2013
(Chapters 13-20 in Klein)
(9 pts) Give the expected major product(s) under the following conditions, and then give a brief mechanistic
explanation for your choice. The use of pertinent resonance structures will help in your answer.
3720 Exam 1 2011
(Chapter 19 in Klein)
(8 pts) The four isomeric compounds shown below are very closely related pharmaceuticals that have
quite similar NMR, MS, UV, and IR properties. Indicate which molecule matches the 13C spectrum
below and explain why you chose that molecule. There will be no credit for simply guessing a
compound.
The highlighted compound has two symmetrical aromatic rings so there will be double signals in the 13C spectrum. The other three compounds will have 15 signals each in their spectra 3720 Exam 1 2011
(Chapter 16 in Klein)
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
a. b. c. d. e. 1. Br2, FeBr3
2. Mg, ether
Br
MgBr
2.
OMgBr
3.
OH
4.
3. H2C=O
4. H3O+
1. (CH3)2CHCl, AlCl3
2. CH3COCl, AlCl3
O
1.
OH
3.
2.
O
ONa
4.
3. KMnO4, heat
4. NaOH
O
O
1. HNO3, H2SO4
2. Sn, HCl
1.
NO2
NH2
2.
3.
O
NH2
NH2
Cl
+
3. Cl2, FeCl3
Cl
D
D
Br
1. CH3CH2Cl, AlCl3
2. Br2, heat
1.
2.
3.
4.
3.
4.
SO3H
SO3H
3. NaOCH3, heat
4. D2, Pt
O
1. CH3COCl, AlCl3
2. SO3, H2SO4
3. Zn, HCl
4. NaOCH2CH3
3720 Exam 1 2011
1.
(Chapter 19 in Klein)
1.
O
2.
SO3Na
(12 pts) A newly produced organic pharmaceutical compound is found to have the formula C13H15NO2
and its mass spectrum shows M+ = 217. Significant signals are seen in the IR spectrum at 2250, 1730,
800, and 720 cm-1. The compound is soluble in organic solvents such as ethyl acetate, acetone, as well as
CDCl3 with the NMR spectra below being taken in the latter. Provide a structure for the organic
compound that matches the data, and then match the protons in the molecule to the 1H NMR signals.
Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1 1
H NMR (ppm): 1.13 (d, 6H, J = 6.9 Hz), 2.72 (t, 2H, J = 7.0 Hz), 3.19 (septet, 1H, J = 6.9 Hz), 3.53 (t, 2H, J = 7.0 Hz), 7.71 (t, 1H, J = 6.5 Hz), 8.10 (d, 1H, J = 6.5 Hz), 8.25 (d, 1H, J = 6.5 Hz), 8.42 (s, 1H) 13
C NMR (ppm): 22.3 (double), 41.3, 63.1, 75.5, 112.5, 118.6, 129.3, 132.0, 133.1, 136.6, 137.4, 198.1 Mass spectrum shows that the formula of the compound is C13H15NO2 as given and the IR signal at 2250 suggests a nitrile (cyano) group (unsat’n of 2). IR signal at 1730 and 13C NMR signal at 198.1 ppm indicates a ketone (unsat’n of 1). IR signals at 800 and 720, as well as signals at 7.5‐8.5 and 112‐137 in the 1H and 13C spectra respectively, point a meta‐
disubst’d aromatic ring (unsat’n of 4). 3720 Exam 1 2011
(Chapter 16 in Klein)
(12 pts) Give the expected major product(s) from the following acylation reaction, and then a complete
mechanism for the conversion that includes resonance structures for the intermediate formed.
3720 Exam 1 2011
(Chapter 19 in Klein)
(15 pts) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials
as sources of carbon. Then give a detailed synthesis of the compound that shows each product formed
along the way. You have access to all of the usual reagents in the lab, as well as techniques for
separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.
3720 Exam 1 2011
(Chapters 13-19 in Klein)
(12 pts) Provide the products from each step of the following synthetic scheme and then, on the NMR
axis given below, draw the expected 1H spectrum of the final product.
1. (CH3)3CCl, AlCl3
O
2.
Cl
1.
, AlCl3
2.
3.
3. NH2NH2, KOH,
4. Br2, heat
5. 2 Li, ether
6. D2O
O
4.
5.
6.
Br
D
Li
1.35
1.35
1.35
7.41
7.41
7.21
0.90
7.21
2.8
D
1.7
8
3720 Exam 1 2011
7
6
5
4
PPM
3
2
1
0
(Chapters 13-19 in Klein)
(10 pts) Give the expected major product formed under the following reaction conditions, and then give
a detailed mechanism for the conversion. (Hint – the major organic product has the formula C10H18O).
3720 Exam 2 2011
(Chapters 13-14 in Klein)
(10 pts) In the boxes provided, give the expected major product from each step of the following reaction
sequence. The spectroscopic clues might help you work out structures.
3720 Exam 2 2011
(Chapters 13-21 in Klein)
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
O
a. b. c. OH
1.
2.
Br
OH
4.
3.
OH
3. NaOCH3, CH3OH,
4. OsO4, NaOH, H2O2
1. m-CPBA, CH2Cl2
2. PhMgBr, ether
OMgBr
O
1.
2.
OH
O
3.
Ph
Ph
4.
Ph
3. H3O+ (quench)
4. PCC, CH2Cl2
CH2OH
1. Na2Cr2O7, H2SO4
2. xs CH3OH, cat. H+
OH
1.
2.
OCH3
Ph Ph
3.
O
O
Ph Ph
4.
OH
OMgBr
3. 2 eq. PhMgBr, ether
4. H3O+ (quench)
d. e. 1. NaBH4, CH3OH
2. HBr
1. CH3COCl, AlCl3
2. NaBD4, CH3OH
OH
2.
1.
ONa
3.
D
D
O
O(CH2)3CH3
4.
D
3. NaH, ether
4. CH3CH2CH2CH2Br
O
1. LiAlH4, ether
2. H3O+ (quench)
1.
H O-AlX3
3. H3PO4, heat
4. Zn, CH2I2, ether
3720 Exam 2 2011
(Chapters 13-19 in Klein)
OH
2.
3.
H
4.
H
(8 pts) Explain the vastly different equilibrium constants observed for the following two hydration
processes.
For the ketone the equilibrium heavily favours the carbonyl and not the hydrate; the carbonyl is stabilized by electron donation from the two alkyl groups and the hydrate experiences strain due to the two bulky alkyl groups. In the case of the aldehyde the carbonyl is less stabilized with only one alkyl group and the hydrate is not as crowded since the H is very small. 3720 Exam 3 2011 (Chapter 20 in Klein)
(10 pts) In the boxes provided, give the expected major product from each step of the following
synthetic scheme. The spectroscopic clues might help you work out structures.
OLi
O
KOH, EtOH
O
(CH3)2CuLi
H
H
reflux
H
THF
CH3
H
1
H singlet 9 ppm
H3O+ (quench)
O
O
NaOH
ONa
Na2Cr2O7
OH
CH3
3720 Exam 3 2011
H
H2SO4
aq. EtOH
m.p. = 200 oC
O
CH3
IR = 3400, 1750 cm-1
(Chapter 22 in Klein)
CH3
IR = 1750 cm-1
(9 pts) Provide a detailed mechanism, including resonance structures where appropriate, for the
following Baeyer-Villager reaction and then explain the regiochemical outcome.
O
Cl
O
O
OH
O
O
CH2Cl2
O
Cl
O
OH
O H
O
B:
O
H
O O O
Cl
O
O
H+ transfer
HO O O
O
Cl
HO O O
H
Cl
The more highly substituted (and hence more electron‐rich) group migrates to the electron‐poor oxygen. 3720 Exam 3 2011
(Chapter 20 in Klein)
OH
(20 pts) Give the major organic product(s) expected from each step in the following conversions. You
do not have to provide mechanisms.
a. b. c. d. e. 3720 Exam 3 2011
(Chapters 13-22 in Klein)
(9 pts) Provide a synthesis of the molecule below that uses only the given starting materials as sources of
carbon. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, PPh3, CuI,
etc.), as well as techniques for separating isomers (i.e. distillation, chromatography, etc.) as needed. No
need to show a retrosynthesis unless it helps.
3720 Exam 3 2011
(Chapters 13-23 in Klein)
(9 pts) Give a detailed mechanism for the following conversion that includes important resonance
structures for intermediates that are formed.
O
O
H
O
NaOCH3, CH3OH
+
reflux
H
OCH3
OH O
O
O
H OCH3
O
H
O
H
3720 Exam 3 2011
(Chapter 22 in Klein)
O
H
OCH3
(9 pts) Give the expected major product formed under the following reaction conditions, and then give a
detailed mechanism for the synthetic sequence that includes important resonance structures for
intermediates.
1. :PPh3, ether
Br
2.
3.
Li
, THF
O
- Ph3P=O
H
Ph3P
Li
O
PPh3 Br
O
Ph3P
PPh3
O
PPh3
3720 Exam 3 2011
(Chapter 20 in Klein)
(12 pts) Give the expected major product from each step of the following reaction sequence. No need to
show any mechanisms.
1. PCC, CH2Cl2
2. LDA, THF, -78 oC
OH
3. CH3CH2CH2Br
1.
O
2.
OLi
3.
O
4.
OH
5.
ONa
6.
O
4. NaBH4, CH3OH
5. NaH, THF
6. CH3CH2CH2Br
3720 Exam 3 2011
(Chapters 13-22 in Klein)
(8 pts) Provide a complete mechanism for the following conversion that includes resonance structures
for intermediates that are formed.
O
O
O
KOH, EtOH
H
reflux
O
O
RO
O
O
O
O
O
O
O
O
O
H
O
3720 Exam 3 2011
O
OH
RO
H OR
(Chapter 22 in Klein)
(6 pts) The following sequence fails to give the product shown; explain why and then give a modified
procedure (showing all intermediate products) that results in the formation of the desired compound.
O
O
1. Mg, ether
O
2.
Br
OH
3. H3O+
H3O+ (hydrolysis)
O
H3CO OCH3
xs CH3OH
cat. H+
BrMg
OH
good chance of intr amolecular
r eaction so ketone needs to be
pr otected f ir st
H3CO OCH3
H3CO OCH3
H3O+ (quench)
O
H3CO OCH3
Mg, ether
Br
3720 Exam 3 2011
BrMg
(Chapter 20 in Klein)
OMgBr
(6 pts) The following spectral data belong to one of the five compounds shown below; circle the correct
structure and match the 1H NMR data to that molecule.
1
H NMR (ppm): 2.34 (s, 3H), 3.30 (s, 3H), 4.80 (s, 2H), 7.16-7.48 (m, 4H)
C NMR (ppm): 21.6, 58.9, 74.8, 124.4, 128.1, 128.5, 129.3, 138.3, 138.7
IR (cm-1):
760, 700
13
3720 Exam 1 2009
(Chapter 16 in Klein)
(12 pts) An unknown organic compound has the formula C6H12O2 from mass spectrometry data and the
following signals in the 1H and 13C spectra. Give a structure for the unknown compound that agrees with
the NMR data and then match the 1H NMR signals to the protons in your answer.
1
H NMR (ppm):
13
C NMR (ppm):
3720 Exam 1 2009
1.13 (d, 6H, J = 6.9 Hz), 2.57 (q, 2H, J = 7.0 Hz), 3.19 (septet, 1H, J = 6.9
Hz), 3.67 (t, 2H, J = 7.0 Hz), 9.72 (t, 1H, J = 7.0 Hz)
22.3 (double intensity), 43.5, 61.2, 75.5, 202.2
(Chapter 16 in Klein)
(12 pts) In the lab you have a bottle of benzene and all of the usual reagents and catalysts required to do
organic synthesis. Beginning with benzene, provide an efficient synthesis of the following compounds
by using any of the reactions and reagents seen thus far in Chemistry 3719 and 3720. Show the organic
product(s) from each step of your syntheses; you may assume that isomer mixtures are separable.
O
NH2
O
O
Cl
HNO3
AlCl3
H2SO4
NO2
(+ trace amounts of o/p isomers separate)
O
Sn
Zn
HCl
HCl
NH2
NH2
3720 Exam 1 2009
(Chapter 19 in Klein)
(20 pts) Give mechanistic explanations for the formation of the products and the regiochemical
outcomes in the following reactions (i.e. draw the mechanisms and use resonance structures to explain
the products).
a)
only isomer f ormed
o
H2SO4, 0 C
H
H
O
The t-butyl group is an o/p
director since it stabilizes
the carbocation f ormed in
those case (one resonance
structure has 3o character);
only the p isomer is formed
here becuase the o positions
are crowded by the very big
t-butyl group.
H
H
3o character
H
O
H
3720 Exam 1 2009
(Chapter 19 in Klein)
(8 pts) Give a detailed mechanism (including resonance structures for the intermediate) for the formation
of the product in the following reaction.
3720 Exam 1 2009
(Chapter 19 in Klein)
(9 pts) Give the major product formed under the following conditions and then a complete mechanism
for its formation. How many signals do you expect to see in the 13C NMR spectrum of the product?
Product is symmetrical so you would see 6 signals in its 13C spectrum.
3720 Exam 2 2009
(Chapter 14 in Klein)
(10 pts) On the axis given below, draw the approximate 1H NMR spectrum for the following molecule.
Label which signals belong to which protons.
3720 Exam 1 2009
(Chapter 16 in Klein)
(10 pts) Give the major products from each step of the following reaction sequence. What will the
upfield region of the 1H NMR spectrum of the final product look like (signal shapes and integration
values)?
3H doublet at ~1 ppm for CH3; 1H quartet at ~2.5 ppm for benzylic CH
D is not magnetically active so it does not show up
Exam 2 2009 (Chapter 13 in Klein)
(16 pts) Give the products A through H from the following sequence. The molecular formula data and
the spectral information might help as clues.
Br
Br2, FeBr3
2 Li
Li
ether
A = C6H5Br
B = C6H5Li
H
O
O
OH
OLi
+
Na2Cr2O7
H3O
H2SO4
(quench)
E IR = 1720 cm-1
D IR = 3200 cm-1
C = C10H13LiO
CH3CH2MgBr, THF
then aq. NH4Cl
OH
F IR = 3200 cm-1
3720 Exam 2 2009
ONa
O
NaNH2
CH3CH2Br
THF
THF
G C12H17NaO
(Chapter 13-19 in Klein)
H 11 signals in 13C
(9 pts) Provide the major organic product, as well as a complete mechanism for its formation, for the
following reaction. How many signals do you expect to see in the 1H NMR spectrum of the product?
Product is symmetrical so you would see 7 signals in its 13C spectrum.
3720 Exam 2 2009
(Chapter 14 in Klein)
(18 pts) Provide a retrosynthesis for each of the following target compounds that goes back to the given
starting materials the sources of carbon. Then give step-by-step syntheses of the target compounds,
showing products from each step along the way.
a.
OH
from
OH
O
OH
Br
Li
Synthesis:
O
OH
Na2Cr2O7
HBr
Br
H2SO4
Li
2 Li
ether
O
aq. NH4Cl
OLi
OH
b.
from
OH
O
OH
Br
MgBr
Synthesis:
m-CPBA
Br
HBr
Mg
MgBr
O
CH2Cl2
ether
O
aq. NH4Cl
OMgBr
3720 Exam 2 2009
OH
(Chapters 13-14 in Klein)
(18 pts) Provide mechanisms for both of the following transformations that include all intermediates and
any important resonance structures.
a.
b.
OH
O
O
+
CH3Li
1. 2 CH3Li, THF
+ HO
2. aq. NH4Cl
H2O
O
+ LiO
O
+
CH3Li
LiO
3720 Exam 2 2009
H
OLi
OLi
(Chapters 13 and 21 in Klein)
H
OH2
(20 pts) Give the major organic products from each step of the following reaction sequences (i.e. when
there is more than one step, a product from each is expected).
a.
b.
c.
d.
e.
3720 Exam 2 2009
(Chapters 13-14 in Klein)
(10 pts) Give a complete mechanism for the following transformation that includes any important
resonance structures for intermediates that may be formed.
Br
1. PPh3, THF
2. CH3CH2CH2CH2Li
Ph3P:
3.
O
- Ph3P=O
PPh3
Ph3P
H
Br
+
O
-
Ph3P
Li
O
Ph3P
Ph3P
O
3720 Exam 3 2009
(Chapter 20 in Klein)
(9 pts) Give a complete mechanism for the formation of the product in the following transformation that
includes resonance structures where applicable. What role do you think the MgSO4 is playing here?
3720 Exam 3 2009
(Chapter 21 in Klein)
(9 pts) Provide a complete mechanism for the formation of the product in the following reaction. How
many signals do you expect to see in the 13C NMR spectrum of the product?
O
O
K+ -OH, ethanol
H
O
reflux
O
O
OR
H
O
O
OH
O
H OR
O
O
Expect to see 10 signals in the 13C spectrum of the product
3720 Exam 3 2009
(Chapter 22 in Klein)
(10 pts) Provide a step-by-step synthesis, showing products from each step along the way, of the
following target compound using only the given starting materials as the sources of carbon. Although
you do not have to show a retrosynthesis, using this technique might help you to solve the problem.
O
OH
from
H
O
OH
O
H
OH
HBr
O
H
Br
PCC
Li
2 Li
CH2Cl2
O
O
50 oC
CuLi
2
O
H
OH
H
H
CuI
ether
KOH, EtOH
H
O
H
ether
OH
+
H
aq. NH4Cl
OLi
H
Note: the retrosynthesis was not required but is included here to show how the problem is solved
3720 Exam 2 2009
(Chapter 22 in Klein)
(20 pts) Give the major organic products from each step of the following reaction sequences (i.e. when
there is more than one step, a product from each is expected).
a.
b.
c.
d.
HO
O
1. PCC, CH2Cl2
1.
2.
NCH2Ph
2. PhCH2NH2, cat. H+
oxidation product
(2o OH to ketone)
e.
3720 Exam 3 2009
(Chapters 22-23 in Klein)
imine formation
(1o amine used)
(16 pts) Give the products A through H from the following sequence. The molecular formula data and
the spectral information might help as clues.
O
O
O
Br2
Cl
AlCl3
Br
FeBr3
F-C acylation
meta bromination
A 13C NMR 200 ppm
B = C9H9BrO
1. LDA, THF
2. CH3CH2Br
BrMg
O
O
Mg
O
Br
O
O
(CH2OH2)
Br
cat. H+
THF
Grignard formation
acetal formation
-alkylation
E = C13H17BrMgO2
D = C13H17BrO2
C IR = 1720 cm-1
CO2
then H+ quench
O
O
O
O
SOCl2
HO
O
O
H3CO
O
O
dilute HCl
H3CO
then CH3OH
pyridine
esterification via acid chloride
Nuc addition to CO2
F 13C NMR = 175 ppm
3720 Exam 3 2009
G = C15H20O4
(Chapters 13-23 in Klein)
acetal hydrolysis
H = C13H16O3
(8 pts) Provide a major product from each step of the following reaction sequence.
OH
H
1. PCC, CH2Cl2
2. (CH3)2C=O, KOH, CH3OH,
O
1.
stops at aldehyde
3. (CH3CH2)2CuLi, THF
4. aq. NH4Cl (quench)
H
O
2.
crossed aldol reaction
OLi
3.
1,4- cuprate addition
O
3.
3720 Exam 2 2009
via the enol form
(Chapter 22 in Klein)
(9 pts) Order the following compounds in terms of their relative reactivity with nucleophiles (1 = most
reactive, 3 = least reactive) and then give a brief explanation for your choices.
O
OCH3
2
The molecule is stabilized by lone pair donation from the O(CH3) group; the highly E.N. O is of similar
size to the carbonyl C so overlap is good, however donation is not as significant as with the less E.N.
N in the amide (3). The OCH3 group is a better L.G. than NHCH3 but not as good as Cl.
1
The molecule is stabilized somewhat by lone pair donation from the Cl; the highly E.N. Cl is larger than
the carbonyl C so overlap is not as good; donation is not as significant as with the O of the ester (2) or
the N in the amide (3). The Cl species is a better L.G. than both NHCH3 and OCH3.
3
The molecule is stabilized by lone pair donation from the NH(CH3) group; the E.N. N atom is of similar
size to the carbonyl C so overlap is good, however donation is more significant than with the more E.N.
O in the ester (2). The NHCH3 group is a worse L.G. than both OCH3 and Cl.
O
Cl
O
NHCH3
3720 Exam 3 2009
(Chapter 21 in Klein)
(9 pts) Order the following compounds in terms of their relative boiling points (1 = highest, 3 = lowest)
and then give a brief explanation for your choices.
O
OH
1
Significant dipoles and strong H-bonding possibilites lead to strong intermolecular interactions
and consequently a higher temperature needed to overcome those interactions and turn the
material from being a liquid to a gas.
2
Significant dipoles but no real H-bonding possibilites lead to weaker intermolecular interactions
and consequently a lower temperature needed to overcome those interactions and turn the
material from being a liquid to a gas.
3
Less significant dipoles and no real H-bonding possibilites result in much weaker intermolecular
interactions and consequently a lower temperature needed to overcome those interactions and
turn the material from being a liquid to a gas.
O
OCH3
OCH3
3720 Exam 3 2009
(Chapter 21 in Klein)