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Organic Chemistry I (Chem340), Spring 2005
First Hourly Exam
This is a closed-book exam. No aid is to be given to or received from another person.
Model set and calculator may be used, but cannot be shared. Please write your name and
WSU ID number at the top of each page. The exam time is 60 minutes. Hand in your
exam papers to the proctor and sign your name at the end of the test.
Good luck and have fun!
For graders only:
Q1
out of 12
Q2
out of 16
Q3
out of 18
Q4
out of 18
Q5
out of 16
Q6
out of 20
Bonus
out of 10
Total
out of 100
Page 1 of 8
Checked by
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Question 1. (12 points) Draw three (3) resonance structures for each of the following species.
Use arrows to show electron movement. Clearly show the formal charge and lone pair electrons.
CH3CO2H
CH2N2
(CH3)2C=CH2
Page 2 of 8
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Question 2. (16 points) List the pKa values for the following acids.
HI
CH3CO2H
FCH2CO2H
MeOH2+
H3O+
HCl
water
NH4+
HBr
CH3CH2OH
Give the products of the following acid-base reactions, and indicate which side is favored at
equilibrium, calculate the equilibrium constant (show the pKa values used for your calculation in
the rationale section).
Reaction
HCl + EtOH
Rationale:
CH3NH2 + EtOH
Rationale:
Page 3 of 8
Equilibrium
Constant
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Question 3. (18 points)
Give the electronegativity values for the following elements.
Li
H
K
B
C
S
N
F
O
Cl
Br
I
Draw the Lewis structures for the following species and show the lone pair electrons. Clearly
indicate the atoms bearing partial negative or positive charge.
BH3
Θ
CH3-BH3
R-NH-Br
O
S
(e.g. NBS, p347)
Cl
Cl
(thionyl chloride, p442)
Page 4 of 8
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Question 4. (18 points) For the following reaction, draw all the possible products (major and
minor). Using the chair conformation, draw all the possible conformers so that the substituents
are in either equatorial or axial positions. Indicate which conformer is most stable conformation
and which is least stable among all the conformers (maybe from different products), and provide
your rationale.
+ HBr
Page 5 of 8
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Question 5. (16 points) Supply the missing information in the table. In the structure column,
indicate all the carbon atoms that give rise to unique 13C signals in the NMR. Two examples to
label the unique carbon atoms are depicted below.
B
A
Structure
A
or
2
1
1
Common Name
Systematic Name
(Trivial Name)
(IUPAC Name)
tert-butyl alcohol
chloroethene
Not applicable.
Page 6 of 8
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Question 6. (20 points) Using the bond dissociation energies given in the table attached at the
back of this exam, calculate the enthalpy change (heat released or absorbed) of the reaction in
the direction it is drawn. Write down the individual bond energy value used in your calculation.
+
HBr
Br
Assuming the entropy change is negligible, calculate the equilibrium constant for the reaction at
-1
-1
25 ºC. Remember ∆ Gº = –RT ln Keq, (R = 1.986 cal mol K , K = ºC + 273). Indicate in which
direction the reaction is favorable.
Page 7 of 8
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Question 6 (continued).
Calculate the equilibrium constant for the following reaction. Which direction is favorable?
NaOH +
Br
+
NaBr + H2O
Bonus question (10 points) Most salts, such as NaHCO3 and NH4Cl, are not volatile, i.e. it is
difficult to convert them into gas even under reduced pressure. However, NH4HCO3, commonly
known as the “smelling salts” or “Hart’s Horn” in baking, can be readily converted into gas under
reduced pressure (e.g. during lyophilization). Explain why ammonium bicarbonate is volatile.
Page 8 of 8