CHE 230 Organic Chemistry
Exam 3, November 17, 1999
Name
Student ID No.
Before you begin this exam:
First: You are allowed to have a simple model set at
your seat. Please put away all other materials. Second: Place your student
identification on your desk. A proctor will come around to check everyone’s ID. Third:
Read through the entire exam. Your goal, as always, is to score as many points as
possible. Do not waste time on problems that you can’t do if there are others that look
easy. Fourth: It is critically important that your answers be written in a clear,
unambiguous manner. Answers in which your intentions are unclear will not receive
credit. Fifth: READ THE INSTRUCTIONS FOR EACH PROBLEM.
You have until 8:50 to complete this exam. There will be no extensions, so budget your
time carefully.
Problem Number
Points possible
1.
4
2.
4
3.
30
4.
5
5.
24
6.
5
7.
10
8.
8
9.
10
Total
100
Score
1
1.
(4 points) Rank the following species in order of INCREASING nucleophilicity.
(i.e put a ‘1’ by the most nucleophilic and a ‘4’ by the least nucleophilic)
CN
1
2.
O 3
CH3 CH2 CH2 CH3
4
(4 points) Which of the following is the best electrophile in Sn2 reactions? (circle
one)
CH3 Br
3.
Br
2
Br
Br
OCH3
(30 points) Provide the major organic product from each of the following
reactions. You do not need to show mechanisms. In all cases, the final product is
a neutral compound. Show stereochemistry wherever relevant. If you believe
that no reaction will occur under the conditions shown, write No Reaction.
a)
t-BuO K
Br
t-BuOH
b)
CH 3CH 2CH 2CH 2 C C H
1. NaNH2
2. CH3 CH2 CH2 Br
CH3 CH2 CH2 CH2C CCH2CH 2CH 3
c)
Br
t-BuO K
t-BuOH
2
d)
N
ClCrO3 H
O
O
(PCC)
OH
H
O
CH2 Cl2
e)
I
Li CN
H
DMSO
CN
H
f)
1. NaH
OH
4.
2.
O
Br
(5 points) In the E2 elimination of the labelled bromocyclohexane shown below,
which cycloalkene is formed? (Circle one) Note: The reactivity of deuterium (D)
is essentially the same as normal hydrogen (H).
Br
D
H
H
D
EtO Na
H
EtOH
D
H
H
D
D
H
H
3
5.
(24 points) The synthetic methods we have discussed can be used to make a
wide range of compounds from simple starting materials. Provide the reagents
needed to convert 1-butanol into each of the products shown below. More than
one step may be required in some cases.
OH
1. PBr3
2. NaCN
PCC
PBr3
CrO3 ,
H2SO 4
O
CN
H
OH
Br
O
6.
(5 points) Propose a viable synthesis of the ether below, starting with any nonether starting materials you wish. Only one or 2 steps is required. You do not
need to show mechanisms, but be alert to conditions that favor substitution over
elimination.
O CH3
NaH
CH3 -I
OH
O
Na
O CH3
This approach avoids competing elimination
CH3 OH
O CH3
∆
This approach will work (although some E1 will occur)
Br
CH3 O Na
Br
This approach will result in E2 elimination, not substitution
4
7.
(10 points) Propose a viable synthesis of the compound below. You may use any
compounds of 3 carbons or less, and you may use any required acids or bases.
CH2 C C CH2 CH3
HO CH2
H
C
C H
NaNH2
H
C
C
CH3 CH2 Br
H
C
CCH2CH 3
NaNH2
O
O
C
CCH2CH 3
C
CCH2CH 3
H2O
CH2 C C CH2 CH3
HO CH2
8.
(8 points) Draw the mechanism for the Sn1 substitution reaction shown below.
Be sure to use the mechanism arrows properly!!!
CH3 OH
Br
∆
OCH3
CH3 OH
Br
O
H
CH3
CH3 OH
OCH3
5
9.
(10 points) Provide a viable mechanism for the reaction shown below. Be sure
that you make proper use of the arrows..
CH3
N
CH3
CH3
N
CH3
∆
Cl
CH3
N
CH3
Cl
CH3
N
CH3
Cl
Cl
CH3
N
CH3
CH3
N
CH3
H
CH3 CH3
N
H
H
Cl
I would accept either pathway
END OF EXAM
6