1
CH341/CH540, Exam 4 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. _______________ (24)
Page 5. _______________ (14)
Page 3. _______________ (24)
Page 6. _______________ (12)
Page 4. _______________ (16)
Page 7. _______________ (10+)
Total _______________ (100)
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
53
I
54
21
22
23
24
25
26
27
28
29
30
39
40
41
42
43
44
45
46
47
48
127
2
1. Give the major organic product of each of the following reactions. If no reaction will occur, write
“No Reaction”. If a mixture of ortho and para products would form, draw only the para.
a.
NO2
HO 3S
NO2
SO3
H2SO4
b.
Br
H3C
CH
Br2
CH3
FeBr3
c.
H3C
CH3
H3C
O
H 3C
O
Cl
CH
O
C
AlCl3
O
d.
O
OH
1. KMnO4, H2O,
reflux
OH
2. H3O+
e.
O
O
CH3
OH
C
CH2CH2CH3
MgBr
H3C
+
2. H3O+
CH3
f.
CH3
C
Cl
CH3
AlCl3
H3C
CH3
3
2. Fill in the needed reagents and conditions over the arrows. An arrow may require more than one step.
a.
H2N
O
N
H+ (cat.)
CH3
b.
CH3
OCH2CH3
O
2 CH3CH2OH
OCH2CH3
+
H (cat.)
CH3
CH3
c.
OH
O
1. NaCN 2. H2SO4 or
C
NaCN/HCN
CH3
CH3
3. Give IUPAC names for the following structures.
a.
CH2CH3
H
O
4-ethyl-7-phenyloctanal
CH3
b.
O
Cl
OH
CH
CH3
CH3
5-chloro-2-isopropylbenzoic acid
N
4
3. Give reasonable arrow-pushing mechanisms for the following reactions. Show all important
resonance forms.
a.
H2N
Cl
H2N
Cl
+ H
FeCl3
Cl
Cl
Cl
Cl
Cl
AlCl3
Cl
-
H2N
AlCl3
H2N
H2N
H
H
Cl
-
Cl
Cl
H2N
H2N
+
Cl
H
AlCl3
H2N
+
H
Cl
Cl
Cl
b.
O
O
H+ (cat.)
+
H
H
OCH3
OCH3
H
H
O
O
H
+
O
+
H
O
H
OCH3
H
O
H
O
CH3
H
OCH3
OCH3
H
Cl
5
4. Multiple Choice: Choose the best answer for each of the following questions.
1.
In electrophilic substitution reactions, a -Br group is:
A. Meta directing and activating
B. Meta directing and deactivating
_________
C. Ortho-para directing and activating
D. Ortho-para directing and deactivating
2.
The compound to the right is (was):
D
NO2
A. A crown ether
B. An explosive invented by Alfred Nobel
_________
C. An antimicrobial compound synthesized by Dr. Hathaway
D. An oxidizing agent
3.
Which reaction is reversible?
CH3
B
O2N
A. Nitration of benzene
B. Bromination of benzene
_________
C. Acetal formation
D. Friedel-Crafts Acylation
4.
Which benzene ring is the least activated towards electrophilic substitution?
C
A.
C.
D.
O
D
O
F
_________
5.
B.
H3C
H3C
N
O
Which TWO statements are true?
A. All ortho-para directors are activating groups.
B. All activating groups are ortho-para directing.
C. All ortho-para directors are deactivating groups.
_________
D. All deactivating groups are ortho-para directors.
E. All meta directors are deactivating groups.
F. All deactivating groups are meta-directors.
6.
Which statement is true about benzene?
B, E
D
_________
Draw the
structure of
acetaldehyde.
A.
B.
C.
D.
It is less stable than a hypothetical cyclohexatriene.
It is an equilibrium mixture of two similar structures.
It is the smallest aromatic compound.
It is shaped like a regular hexagon.
O
H3C
C
H
-
+
NO2
6
5. Show how you would synthesize the following products from the indicated starting materials, plus
any other reagents.
Product
Starting Material
a.
N
H3C
C
CH3
O
CH2CH3
H3C
O
C
H
1. CH3CH2MgBr
2. H3O+
H2NCH3
H+ (cat.)
H3C
C
OH
CH2CH3
CrO3, H2SO4, H2O
H3C
CH CH2CH3
b.
O
I
H3C
CH2CH3
ClCH2CH3
AlCl3
I2/HIO4
O
O
H3C
H3C
C
AlCl3
CH2CH3
Cl
CH2CH3
7
6. What are the four “rules” for an aromatic compound?
1. Cyclic
2. Planar (flat) or nearly so
3. Every ring atom has a p-orbital
4. 4N + 2 pi-electrons in the system of p-orbitals, (N = 0, 1, 2, 3…)
Classify the following structures as aromatic, anti-aromatic, or non-aromatic. Briefly explain your
reasoning. Don’t merely say, “It follows the rules,” or something similar.
H
N
H
Cyclic, flat, p-orbital on each ring atom, but only
12 electrons in the p-orbitals, so it can’t be
aromatic. 12 is a 4N number, so it is antiaromatic.
H
H
H
Cyclic, flat, p-orbital on each ring atom, and 6
electrons in the p-orbitals, so it is aromatic.
Bonus! If 1,4-di-tert-butylbenzene is treated with 2-chloro-2-methylpropane and AlCl3, and heated, the
major product is 1,3,5-tri-tert-butylbenzene. Explain how this forms, and why.
CH3
CH3
C
CH3
H3C
H3C
C
CH3
CH3
C
CH3
CH3
Cl
C
CH3
CH3
AlCl3
H3C
H3C
C
C
+ H
Cl
CH3
CH3
CH3
CH3
CH3
The t-butyl group adds ortho to one of the t-butyl groups on the ring. Two t-butyl groups next to each
other causes a lot of steric hindrance, which isn’t good.
CH3
CH3
CH3
H
CH3
C
+
C
CH3
CH3
+ H Cl
H
C
CH
3
3
H3C
CH3
C
C
C
C
H
C
CH3
3
H3C
CH3
CH
CH
3
3
CH3
CH3
H+ adds to the ring, and a t-butyl group comes off as a cation.
8
H
H3C
H3C
C
CH3
C
+
CH3
CH3
CH3
H3C
CH3
CH3
C
CH3
CH3
CH3
C
H
H3C
H3C
The t-butyl group adds meta to minimize the steric hindrance.
CH3
C
C
CH3
CH3
CH3