1
CH341/CH540, Exam 3A Key, Fall 2009
______________________________________
Name
This exam consists of several parts of unequal difficulty. Look over the whole exam right now, and start
on something you know well. If you don’t know something, skip it, and come back to it later. Use your
time wisely.
Keep Your Eyes On Your Own Paper!
Grading Summary
Page 2. _______________ (18)
Page 5. _______________ (10)
Page 3. _______________ (30)
Page 6. _______________ (12)
Page 4. _______________ (24)
Page 7. _______________ (6 +)
Total ___________________
A Partial Periodic Table of the Elements
1A
IIA
IIIB
IVB
VB
VIB
VII
B
VIII
IB
IIB
IIIA
IVA
VA
VIA
VII
A
1
H
VIII
A
2
He
1.01
4.00
3
Li
4
Be
5
B
6
C
7
N
8
O
9
F
10
Ne
6.94
9.01
10.8
12.0
14.0
16.0
19.0
20.2
11
Na
12
Mg
13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
23.0
24.3
27.0
28.1
31.0
32.1
35.5
40.0
19
K
20
Ca
31
Ga
32
Ge
33
As
34
Se
35
Br
36
Kr
39.1
40.1
69.7
72.6
74.9
79.0
79.9
83.8
37
38
49
50
51
52
Te
53
I
54
128
127
21
22
23
24
25
26
27
28
29
30
39
40
41
42
43
44
45
46
47
48
2
1. (12) Give IUPAC names for the following structures. Use R, S, E, or Z, when needed.
a.
CH3
H3C
OH
CH3
(E)-4.5-dimethylhex-3-en-1-ol
b.
C
O
CH2CH3
C
5-ethoxycyclooctyne
2. (6) Predict which member of each pair will be more soluble in water. Explain your reasoning.
a.
CH3
H3C
OH
or
H3C
C
OH
CH3
Both can hydrogen-bond with water. The right molecule is more compact (ball-like), so it will have less
non-polar surface area than the more linear molecule on the left. Therefore, the right molecule is more
polar, so it is more water soluble.
b.
H3C
CH3
or
H3C
O
CH3
Both have the same size and shape. The ether on the right can hydrogen-bond with water using its
electronegative O. The alkane on the left cannot hydrogen bond with water, so it is much less watersoluble.
3
3. (30) Draw the major organic product of each of the following reactions.
a.
O
Na2Cr2O7
OH
OH
H2SO4, H2O
b.
O
HO
S
H
CH3
H3C
O
Cl
S
O
H
O
pyridine
CH3
O
H3C
c.
H
O
OCH3
HO
NaBH4
OCH3
CH3OH
O
d.
O
O
H3C
CH MgBr
+
H
H3C
C
2. H3O+
H3C
CH C
H3C
Cl
e.
2 HCl
CH3CH2 C
C
H3C CH2 C
H
H
H3C
C
C
CH3
CH3
Cl
f.
2 Na
liquid NH3
CH3
C
H3C
C
H
OH
H
4
4. (24) Supply the needed reagents and experimental conditions to accomplish each of the following
transformations. More than one step may be required in some cases.
a.
H2O
CH3
b.
CH3
H2SO4 (cat.)
OH
Br
H3C
C
Molten KOH
CH2 CH3
200 °C
H3C
C
C
CH3
Br
c.
1. NaNH2
CH3CH2 C
C
H
2.
O
H
C
HO
CH3
CH3CH2 C
CH CH3
C
3. H3O+
OH
d.
Cl
Conc. HCl, heat
or SOCl2
e.
O
1. Mg
Br
H3C
f.
C
2. CO2
3. H3O+
C
2 H2, Pd cat.
O
H3C
OH
CH2 CH2
O
5
5. (10) Multiple Choice: Choose the best answer to each question.
1.
Which alcohol is used in alcoholic beverages?
B
_________
A.
B.
C.
D.
2.
Which compound is the strongest acid?
C
A.
B.
C.
D.
_________
3.
Methanol
Ethanol
2-Propanol
1,2-Ethanediol (“Ethylene glycol”)
Methanol
Acetylene
Phenol
Diethyl ether
Which of the following compounds does not react with a Grignard reagent?
A.
B.
C.
D.
D
_________
Methanol
Acetylene
Acetone
Diethyl ether
4.
Which alcohol is not easily oxidized by CrO3/H2SO4/H2O?
D
A.
_________ HO
5.
B
B.
C.
H
C
H
H
HO
C
D.
H
CH3
HO
C
CH3
CH3
HO
H
H
CH3
Which of the following is a primary alcohol?
A.
_________ HO
B.
H
C
H
H
HO
C
H
CH3
HO
C
CH3
CH3
CH3
C.
H
H
C
D.
CH3
CH3
HO
C
CH3
CH3
6
6. (12) Write acceptable arrow-pushing mechanisms for the following reactions.
a.
CH3
CH3
H Br
H3C C O CH3
H3C C Br + H O CH3
CH3
CH3
Br
-
Br
CH3
CH3 H
H3C
C
O
H3C
CH3
+
-
C
H
O
O
H
CH3
CH3
b.
CH3
H3C
H3C
+
MgBr
C
O
2. H3O+
H3C
H
H
CH3
H3C
C
O
+
O
-
MgBr
CH3
H
H3C
C
CH3
CH3
7
7. (6) How would you synthesize the following product from the indicated starting material? You do not
need to draw the mechanisms. If you show intermediate structures, I can more easily give you partial
credit.
Product
Starting Material
CH3
Br
CH2
H2SO4, heat
CH3
OH
CH3
Mg, ether
O
1. H3C
C
CH3
MgBr
2. H3O+
Bonus: (5) An inexperienced graduate student moved into a laboratory and began work. He needed
some diethyl ether for a reaction, so he opened an old, rusty can marked “ethyl ether” and found there
was a half gallon left. To purify the ether, the student set up a distillation apparatus, started a careful
distillation, and went to the stockroom for other reagents he needed. While he was in the stockroom, the
student heard a muffled “boom”. He quickly returned to the lab, to find a worker from another
laboratory putting out a fire. Most of the distillation apparatus was embedded in the ceiling.
A. Explain what probably happened.
The old ether probably had reacted with oxygen in the air and formed peroxides. When the ether
distilled off, the peroxides exploded.
B. Explain how this near-disaster could have been prevented.
First, he could have checked the ether for peroxides first. Second, he shouldn’t have left the lab
and left the distillation unattended.