Additional Problems for practice:
1. Draw a mechanism for the following transformations, using the curved arrow
notation to indicate the reorganization of electron density. Show all intermediates,
unshared electrons, formal charges and countercharges where appropriate.
Explain why a racemic mixture is formed in (a):
O
HO
H
1. CH3CH2Li
CH3
H
(a)
+ LiOH
2. H2O
racemic
CH3CH2 ––Li
H
O
LiO
HO
H
H
H
+ LiOH
a racemic mixture is formed because ethyllithium can attack from either face
of the aldehyde carbonyl
OH
1. LiAlH4
(b)
O
ether
2. H3O+
H
H
-
Al
H
Li+
H
H
OLi
O
OH
H
H
H
MgBr
1.
O
(c)
2. H3O+
O
OH
OH
+
O-
O
O-
O
MgBr
OH
+
H3O+
OH
OMgBr
H
H
O
H
2. Write the major product of each of the following reactions:
O
OH
1. LiAlH4/ ether
(a)
2. H3O+
OCH3
O
HO
Mg(0)
(b)
Br
ether
MgBr
O
CH3
(c)
product of (b)
HO
CH3
ether
O
product of (b)
(d)
OH
ether
I
(e)
2
4Li
CuI
ether
ether
Br
ether
3. Devise four different syntheses of 2-methyl-2-hexanol starting with each of the
following compounds:
H 3C
OH
CH3
H 3C
2-methyl-2-hexanol
CH3
Br
Mg
1.
CH3
BrMg
O
OH
H 3C
(a)
H3C
CH3
CH3
Ether
H 3C
2. H3O+
(a)
CH3
CH3
H3C
H 3C
2. H3O+
(c)
OCH3
OH
H 3C
1. CH3MgBr
O
1. 2 CH3MgBr
OH
H 3C
CH3
2. H3
O
O+
H 3C
1.
(d)
HgSO4
CH3
BrMg
O
CH3
H2SO4
H2O
H3C
CH3
Ether
2. H3O+
H3C
OH
CH3
H3C
Additional Problems for practice:
1. Design a synthesis of the following racemic cyclopropane starting from acetylene,
organic compounds containing three or fewer carbons, and any inorganic reagents
necessary. Note with a star each step that creates a chiral product, explain why
each starred step affords a racemic mixture.
Retrosynthetically:
* CH2I2, Zn/Cu
H
H
CH3
H3C
CH3
Simmons-Smith H3C
cyclopropanation
racemic:
carbene can approach both
sides of alkene
H2/ Pd
BaSO4
quinoline
I
H3C
H3C
CH3
CH3
SN2
NaNH2
I
NaNH2
CH3
H
H
CH3
SN2
H
H
acetylene
2. Outline a preparation of racemic disparlure from acetylene and any other
compound containing not more than five carbon atoms. Note with a star each step
that creates a chiral product, explain why each starred step affords a racemic
mixture
Retrosynthetically:
*
H
O
H3C(H2C)9
MCPBA
H
H
H3C(H2C)9
CH2Cl2
(CH2)4CH(CH3)2
H
(CH2)4CH(CH3)2
H2/ Pd
BaSO4
quinoline
racemic: peracid
can approach either face of
alkene pi bond
I
(CH2)3CH(CH3)2
(CH2)3CH(CH3)2
H3C(H2C)8
H3C(H2C)8
SN2
NaNH2
I
NaNH2
H3C(H2C)8
H
H3C(H2C)8
H
H
SN2
acetylene
Alkyl halide prep:
1. TsCl,
pyridine
I
1.
O
BrMg
HO
2. NaI
H
2.
1. TsCl,
pyridine
H3O+
Mg
Br
I
OH
2. NaI
BH3•THF
H2O2, HO2
I
Br
+ 4Li
CuI
3. Explain how you could accomplish the following isomerization in a three-step
sequence:
H
H
H
H
Br2
H2, Pd
BaSO4, quinoline
Br
H
Br
xs KOH
H
4. Propose a structure for the unknown compound given the following data:
COOH
KMnO4, conc
unknown compound
KOH
O
+ 1 mole
COOH
HOOC
H 3C
OH
no CO2 evident
No CO2 means no terminal alkene present; since there is only 1 mole of acetic acid given off
but we have three carboxylic acids, there must be a ring in the original molecule
H
H
H
CH3
H
or
Additional Problems for practice:
Additional Problems for practice:
1. Provide proper IUPAC names for the following:
CH3
(b)
(a)
2,2-dimethylhex-3-yne
octa-2,5-diyne
(c)
(E)-3,6-dimethylhept-2-en-4-yne
(Z)-3,6-dimethylhept-2-en-4-yne
or
(d)
(E)-hexa-1,3-dien-5-yne
(e)
3-ethyl-6-isopropyloct-4-yne
4. How might you prepare the following compounds from acetylene and any needed
alkyl halide?
Retrosynthetically:
a.
CH3I
H2C
CH3
H2C
SN2
NaNH2
Br
H 2C
H
H 2C
H
NaNH2
H
H
b.
I–CH2CH3
H3CH2C
CH2CH2CH(CH3)2
CH2CH2CH(CH3)2
NaNH2
I–CH2CH2CH(CH3)2
H
H
CH2CH2CH(CH3)2
NaNH2
H
H
c.
I
I
NaNH2
H
SN2
cyclodecyne
SN2
I
NaNH2
H
H
I
H
+
3. How would you accomplish the following conversion (2 steps):
H
H
Br2
xs KOH, 200°C
Br
H
Br
H
4. Assuming that H2/Pd can reduce alkynes to alkanes, how would you synthesize
the following compound starting with styrene, and using only the reagents Br2,
HBr/peroxides, NaNH2, and H2/Pd? More than one step is needed.
H
CH2
styrene
HBr
ROOR
heat
Br
H
H
Br2
H
Br
CH2
CH2
NaNH2
Br
H
Na
NaNH2
SN2
Br
H2, Pd