Massachusetts Institute of Technology
Dr. Kimberly L. Berkowski
5.13, Fall 2006
Organic chemistry II
EXAM #3 EXTRA PROBLEMS
What to expect on Exam #3:
1.
2.
3.
4.
5.
6.
~1 Labeling experiment
~2 Mechanisms
~2 Syntheses
~5 Transformations – supply missing product
~5 Transformations – supply missing reagents
~3 General question
1. (4 points each, 8 points total) In the boxes, please provide the reagents for the
illustrated transformations. More than one step may be required.
(a)
i-Pr
O
Br
i-Pr
OH
(b)
O
i-Pr
O
i-Pr
OH
H
Figure by MIT OCW.
2. (2 points each, 8 points total) Please provide the products of the following reactions. If
no reaction is expected, write “NR”.
(a)
O
Et
(b)
1. Excess Na BH4
Cl
O
Et
(c)
1. Excess MeMgBr
OH
O
Et
(d)
2. Workup
1. Excess MeLi
OMe
O
Et
2. Workup
2. Workup
1. Excess LiAlH4
NMe2
2. Workup
Figure by MIT OCW.
Name_____________________
1
3. (2 points each, 16 points total) Please provide the requested products or reagents. If no
reaction is expected, write “NR”.
(a)
O
Me
Me
NH2
Me
NH2
H2O2, ∆
Me
(b)
O
Me
H2N
Me
1. LiAlH4
OH
cat. H+
2. workup
(c)
O
n-Bu
NH2
n-Bu
CN
H3O+
H2O
(d)
NH2
N2
Br
Figure by MIT OCW.
Name___________________
2
4. (11 points) Provide a detailed mechanism for the illustrated conversion of acetic acid
(A) to acetyl chloride (B).
O
Me
OH
A
+
Cl
O
S
O
Cl
Cl
Me
+ SO2
+
HCl
B
Figure by MIT OCW.
Name___________________
3
5. (11 points each, 22 points total) Please provide syntheses for only two of the three
indicated compounds. All the carbon atoms should be derived from the allowed starting
materials. You may use any common reagents.
Allowed Starting Materials:
Me
Me
CO2
Me
Me
Pick Two:
C
Me
Me
N
Me
OH
Me OH
HO Me
Me
Me
H
N
Me
Synthesis # 1:
Figure by MIT OCW.
Name___________________
4
5. (Continued)
Allowed Starting Materials:
Me
Me
Me
Pick Two:
Me
Me
C
Me
N
CO2
OH
Me
Me-OH
HO Me
Me
Me
H
N
Me
Synthesis #2:
Figure by MIT OCW.
Name_______________________
5
6. (11 points) Provide a synthesis that will selectively convert A to B. Show all the key
intermediates and furnish all the important reagents. This is not a one-step process.
O
Me
A
O
HO
Me
B
Figure by MIT OCW.
Name_____________________
6
7.
Methyl acetimidate (A) is hydrolyzed in aqueous sodium hydroxide to give mainly
acetamide and methanol (eq 1). In aqueous acid, A hydrolyzes to give primarily
methyl acetate and ammonium ion (eq 2).
a) Provide a detailed mechanism for the illustrated process. Please show all arrow
pushing.
HO-
NH
Me
A
OMe
H2O
O
Me
NH2
+
MeOH
(1)
Figure by MIT OCW.
b) Provide a detailed mechanism for the illustrated process. Please show all arrow
pushing.
NH
Me
A
OMe
excess H+
H2O
O
Me
OMe
+
NH4
(2)
Figure by MIT OCW.
c) Briefly explain why the two reactions provide different products.
7
8.
Synthesize the indicated compounds from the allowed starting materials shown
below. All of the carbons of the target compounds should be derived from the
allowed starting materials.
Allowed starting materials
MeOH Me
OH
CO2 ethylene
O
CN
H
(b) Me
H
N
Me
Me
(c)
NH2
Me
O
Me
N
H
Br
Br
HO
O
Br
(e)
(d)
Me
N
Me
Me
Figure by MIT OCW.
9.
Provide the best stepwise mechanism for the illustrated process. Please show all
arrow pushing.
O
H
H+
NaBH3CN
O
H
NH2
N
Figure by MIT OCW.
10.
(a) Provide the best mechanism. Please show all arrow pushing.
N=C-Me
N
Me
H+
Figure by MIT OCW.
(b) Provide the best mechanism. Please show all arrow pushing.
N
Me
H 2O
H+
NH2
OH
Figure by MIT OCW.
8
11.
Consider the labeling experiments outlined below:
O
(1)
(2)
+
H , H2φ
Me NHMe
O
Stop each reaction at 50% conversion
and examine the recovered starting
material for incorporation of Ø.
+
H , H2φ
Me OMe
Figure by MIT OCW.
Under acidic hydrolysis conditions, would you expect more Ø incorporation into the
amide (eq 1) or the ester (eq 2)? Your answer should include the mechanism for
these reactions.
9