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Hour Exam #4
5.13 Fall 2006
Organic Chemistry II
December 6, 2006
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1. Make sure your exam has 7 numbered pages plus a periodic table.
2. Write your initials on each page.
3. Look over the entire exam before you begin to familiarize yourself with its length. Do
what you know first, then attempt the harder problems.
4. Read the instructions carefully and budget your time.
5. Show all of your work. Partial credit receives points!
1. (3pts) For each molecule, write the correct pKa value for the most acidic proton.
O O
O
O O
OMe
9
25
20
Figure by MIT OCW.
2. (16 pts) Fill in the correct reactants for the following transformations.
Be specific about quantities, where relevant.
1.KCN, HCN
2.LiAlH4 or CH2N2
3.H2O
4.NaNO2,HCl
O
a)
O
b)
Ph
CH3
Ph
CH3
O
d)
O
Br
Ph
1. LDA (1 eq)
Br (1 eq)
2.
O
c)
Br2
AcOH
O
O
CH3
Ph
MgBr2
O
H
Figure by MIT OCW.
3. (24 pts) Provide the missing products for each reaction. Indicate no reaction with
N.R.
(a)
O
Ph
Excess NaOH
CH3
O
(b)
O
Excess I2
Ph
O
+
H3O /H2O
O
+ HCI3
O
D
OMe
O
(c)
O
(d)
H 3C
CH3
CH3
O
O
NaOEt
EtOH
CH3
O
OEt
O
mCPBA
O
CH3
HO
(e)
N
H 3C
CH3
O
H3O+/H2O
N
CH3
Me
(f)
H3O+/H2O
or
HO
O
OH
Figure by MIT OCW.
2
4. (15 pts) Provide a mechanism for the following transformation.
O
H2C
O
Me
+
O
O
Me
OEt
OEt
1 equiv.
Me
O
O
O
OEt
H
+
O
OEt
O
OEt
O
OEt
O
+
+
Me
O
HOEt
O
OEt
OEt
O
+
O
O
OH O
OEt
O
+
H OEt
H
O
OEt
O
O
+ OEt
OEt
HOEt
O H + OEt
H
EtO
O
OH O
H
O
OEt
OEt
O
O
O
OEt
OEt
O
Figure by MIT OCW.
O
+
HOEt
Figure by MIT OCW.
3
5. (14 pts) Provide a mechanism (steps 1 and 3 only)
HO OH
1. H3O+/H2O
2.NaBH4(no mech)
3.H3O+/H2O
+ H
OH OH
OH2
HO
+
H2O
O
H3O
HO
OH2
H
H2O
O
+
NaBH4
H2O H
OH2
OH
+ H2O
Figure by MIT OCW.
H2O
H
H3O
+
Figure by MIT OCW.
4
6. (14 pts) Synthesize the target molecule from methyl acetate. Partial credit will be
given for a retrosynthetic analysis.
O
Me
O
Me
Me
Me
target
2 Me
methyl acetate
1.
O
O O
1 eq OMe
OMe
O
OMe
O O
OMe
(claisen)
2.
OMe
H3O
PBr3
1.LiAlH4
Br
OH
2. H2O
NaOMe
O O
OMe
OMe
O O
NaOMe
OMe
Br
Br
O
CO2
O O
OH
+
H3O /H2O
D
Figure by MIT OCW.
5
7. (14 pts) Synthesize the target molecule from methyl acetate and 2-butanol. Partial
credit will be given for a retrosynthetic analysis.
OH
OH
Me
Me
Me
O
Me
O
Me
OH
OMe
2-butanol
OMe
methyl acetate
target
Cl
PCC
AcOH
Cl2
O
OH
O
2 MeO
O
O
MeO
+
NaOMe
MeOH
NaOMe
MeOH
O
ΝaOH
∆
O
O
O
MeO
O
O
MeO
O
H2O
O
MeO
O
O
NaBH4
O
O
OH
MeO
HO
Figure by MIT OCW.
6
EXTRA CREDIT
(5 pts) Propose a reasonable mechanism for the following transformation.
O
Me
+H
+
H
Me
N
H
Me
H+, cat
O
Me
N
Me
Ph
OH
O
H
Ph
O
+
H
H
O
H
H
H
+
HNMe2
H
H
NMe2
H
PT
OH2
Me
Me
H
H
H
N
H
N
Me
O
Me
Ph
H
+
Ph
O
Ph
N
Me
OH
O H
H
Me
OH2
H 2O
Ph
Me
N
+
H
H
H O
Ph
Me
Me
N
Me
Me
Figure by MIT OCW.
7