NAME _______________________
ID #
_______________________
ORGANIC CHEMISTRY I (2301)
9:45 – 10:35 am, October 6, 2015
Exam 1
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check the box on the right:
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A periodic table is attached to the back of this exam as an aid. Otherwise, you are not
permitted to use any other materials (including notes, books, or electronic devices of
any kind).
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exam begins, please write your name at the top of the next page.
You may use pen or pencil. However, re-grades will be considered only for exams
completed in pen.
Please write your answers in the boxes/spaces provided. If your answer is not in the
appropriate space (say, for example, it’s on the back of the page), draw us an arrow
and/or note telling us where to look.
1
NAME _______________________
Scoring:
1. _________ / 6
5. _________ / 16
2. _________ / 20
6. _________ / 19
3. _________ / 16
7. _________ / 6
4. _________ / 17
Total Score: _________ / 100
1. (6 pts) Draw Lewis dash-bond structures for two constitutional isomers that have
molecular formula C2H2O, and that have no formal charges on any atom. Draw all atoms
and lone pairs of electrons.
2. (20 pts) For each of the molecules on the left, draw as many of the best Lewis dash-bond
resonance structures as there are boxes to put them in. (Feel free to omit lone pairs and C-H’s,
or draw them—your choice.) Then, below each resonance structure, describe whether each
would be a major or minor contributor. Finally, draw a resonance hybrid that illustrates
partial charges and multiple bonds.
resonance structure
contribution:
(major/minor?)
contribution:
2
resonance hybrid
resonance structure
resonance structure
contribution:
(major/minor?)
contribution:
contribution:
resonance hybrid
3. (16 pts) cis-1,3-Cyclohexanediol (shown at right) takes on
two
equilibrating
chair
conformations.
a. In the boxes below, draw these two equilibrating
chair conformers.
b. In cis-1,3-cyclohexanediol, the most stable
conformation is determined by steric interactions,
which destabilize axial –OH substituents. But
there is also a weaker interaction that stabilizes
an axial –OH group. Draw this interaction on one of your chairs.
less stable chair conformation
more stable chair conformation
MORE , LESS ,
c. Would the structure on the right be
or
EQUALLY
polar, compared to the structure
on the left? (Circle one.)
3
d. The equilibrium you drew on the previous page is associated
with an equilibrium constant Keq(diol) and a reaction energy
G(diol). How would you expect these values to compare with
those for cis-1,3-dimethylcyclohexane? Assuming that
Keq(dimethyl) and G(dimethyl) are defined the same as
Keq(diol) and G(diol), by replacing the –OH’s in your drawing
with –CH3’s, would you expect
cis-1,3-dimethylcyclohexane
Keq(diol)
>
,
<
,
or
=
Keq(dimethyl) ? (Circle one.)
G(diol)
>
,
<
,
or
=
G(dimethyl) ? (Circle one.)
4. (17 pts) For each of the Lewis structures drawn below, in the boxes provided:
 Draw Lewis wedge/dashed-bond structures that illustrate the most stable threedimensional structure of the molecule. Draw all atoms, but feel free to omit lone pairs.
 In the boxes provided, write the hybridization state for any atom heavier than hydrogen.
 In the boxes provided, give any bond angle indicated by curved arrows in the original
Lewis structure.
wedge/dashed-bond (3D) structure
angle:
angle:
hybridization
hybridization
hybridization
hybridization
angle:
wedge/dashed-bond (3D) structure
angle:
hybridization
hybridization
hybridization
4
5. (16 pts) Molecules A and B below are both bases.
 Using “electron pushing” (with double-barbed arrows), show how each base would be
protonated in an acid-base reaction.
 In the box on the right, draw the conjugate acid formed from each base.
 Below each reaction, compare the basicity of A/B with other bases by circling the
appropriate answer.
conjugate acid of A:
+
+
A
MORE
BASIC
Is A
MORE
BASIC
than
or
?
Is A
LESS
BASIC
or
?
than
LESS
BASIC
conjugate acid of B:
+
+
B
MORE
BASIC
Is B
or
MORE
BASIC
than
?
Is B
or
LESS
BASIC
LESS
BASIC
5
than
?
6. (19 pts)
a. For isopropyl dimethyl amine (shown at right), in the
boxes below, draw Newman projections that show the
most stable, second-most stable, least stable, and secondleast stable conformations of the molecule. Draw your
projections looking down the central C-N bond, using
the perspective I’ve shown in the drawing.
isopropyl
dimethyl amine
Newman projection for
most stable
conformation
Newman projection for
second-most stable
conformation
Newman projection for
least stable
conformation
Newman projection for
second-least stable
conformation
b. Next,
draw
a
Lewis
wedge/dash-bond structure that
illustrates the most stable threedimensional conformation of
isopropyl dimethyl amine.
wedge/dashed-bond (3D) structure
6
c. What if isopropyl dimethyl amine
were protonated by an acid? What
would
be
the
most
stable
conformation of the conjugate acid
of isopropyl dimethyl amine? Draw
your answer as a Newman projection
in the box at right.
Newman projection for
most stable conformation of
protonated isopropyl dimethyl amine
7. (6 pts) Each of the basic molecules below has multiple
potential protonation sites. Given the pKa values in the
chart on the right, draw the organic product you would
expect if each molecule was combined with just one
molecule of H3O+.
pKa
H 3C
10.6
NH 3
9.5
O
4.7
H 3C
OH
1.0
+
+ H2O
+ H3O
+ H3O+
+ H2O
7
Be
Beryllium
9.01
12
Mg
Magnesium
24.31
Li
Lithium
6.94
11
Na
Sodium
22.99
56
Ba
55
Cs
Ra
Radium
(226)
Fr
Francium
(223)
88
87.62
85.47
87
Lanthanum
Strontium
Rubidium
Barium
57
La
Sr
Rb
137.33
88.91
38
37
Cesium
Yttrium
40.08
39.10
132.91
Y
Calcium
Potassium
(227)
Actinium
Ac
89
138.91
39
44.96
Scandium
Sc
20
Ca
K
3
3B
21
19
3
1.01
(261)
Rutherfordium
5
5B
23
Na
Db
Sg
91
Pa
Protactinium
231.04
Th
Thorium
232.04
140.91
90
Praseodymium
Cerium
140.12
Iron
Ru
44
55.85
Pm
61
(269)
Hassium
Hs
108
190.23
Osmium
Os
76
101.07
Sm
62
(268)
Meitnerium
Mt
109
192.22
Iridium
Ir
77
102.91
Rhodium
Rh
45
58.93
Cobalt
Co
9
8B
27
238.03
Uranium
U
92
144.24
(237)
Neptunium
Np
93
(145)
(244)
Plutonium
Pu
94
150.36
Neodymium Promethium Samarium
Nd
60
59
Pr
58
(264)
Bohrium
Bh
107
186.21
Rhenium
Re
75
(98)
(266)
Seaborgium
Ce
(262)
Dubnium
106
183.84
Tungsten
74
95.94
Tantalum
105
Tc
43
54.94
Fe
26
8
Molybdenum Technetium Ruthenium
Mo
42
52.00
W
180.95
Mn
7
7B
25
Average atomic mass*
Atomic number
Element symbol
Element name
Chromium Manganese
Cr
6
6B
24
22.99
Sodium
Ta
73
92.91
Niobium
Nb
41
50.94
Vanadium
V
Copyright © 2008 California Department of Education
it refers to the atomic mass of the
most stable isotope.
Rf
104
178.49
Hafnium
Hf
72
91.22
Zirconium
Zr
40
47.87
Titanium
Ti
4
4B
22
11
Key
(243)
Americium
Am
95
151.96
Europium
Eu
63
195.08
Platinum
Pt
78
106.42
Palladium
Pd
46
58.69
Nickel
Ni
28
10
(247)
Curium
Cm
96
157.25
Gadolinium
Gd
64
196.97
Gold
Au
79
107.87
Silver
Ag
47
63.55
Copper
Cu
11
1B
29
14
4A
6
Cf
98
162.50
Dysprosium
Dy
66
204.38
Thallium
Tl
81
114.82
Indium
In
49
69.72
Gallium
Ga
31
26.98
Aluminum
Al
13
10.81
Boron
B
Es
99
164.93
Holmium
Ho
67
207.2
Lead
Pb
82
118.71
Tin
Sn
50
72.61
Germanium
Ge
32
28.09
Silicon
Si
14
12.01
Carbon
C
(247)
(251)
(252)
Berkelium Californium Einsteinium
Bk
97
158.93
Terbium
Tb
65
200.59
Mercury
Hg
80
112.41
Cadmium
Cd
48
65.39
Zinc
Zn
12
2B
30
13
3A
5
15
5A
7
(257)
Fermium
Fm
100
167.26
Erbium
Er
68
208.98
Bismuth
Bi
83
121.76
Antimony
Sb
51
74.92
Arsenic
As
33
30.97
Phosphorus
P
15
14.01
Nitrogen
N
(258)
Mendelevium
Md
101
168.93
Thulium
Tm
69
(209)
Polonium
Po
84
127.60
Tellurium
Te
52
78.96
Selenium
Se
34
32.07
Sulfur
S
16
16.00
Oxygen
O
16
6A
8
Lr
103
174.97
Lutetium
Lu
71
(222)
Radon
Rn
86
131.29
Xenon
Xe
54
83.80
Krypton
Kr
36
39.95
Argon
Ar
18
20.18
Neon
Ne
10
4.00
Helium
(259)
(262)
Nobelium Lawrencium
No
102
173.04
Ytterbium
Yb
70
(210)
Astatine
At
85
126.90
Iodine
I
53
79.90
Bromine
Br
35
35.45
Chlorine
Cl
17
19.00
Fluorine
F
17
7A
9
He
2
2A
4
H
Hydrogen
* If this number is in parentheses, then
7
6
5
4
3
2
1
California Standards Test
18
8A
2
Chemistry Reference Sheet
1
1A
1
Periodic Table of the Elements