CHM 221 C: Organic Chemistry I
Test 1: September 22nd, 2010
This test consists of: 10 multiple choice questions, 10 true/false questions, 3 short answer
questions, 5 multi-part questions, and 1 bonus question to total 105 points. Use your time
wisely. You may not want to start at the beginning of the test.
Make sure that you read the entire question and answer each question clearly and
completely.
When you have completed the exam, please consider the following:
I affirm that I have neither committed nor witnessed a violation of academic integrity in
the completion of this exam.
Signed ___________________________________
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Multiple Choice. Choose the answer that best fits the question. There is only one correct
answer for each question. Make sure you circle your answer choice clearly. (2 pts each)
1. What is the IUPAC name of the following?
a. 1-ethyl-4,4-dimethylcyclopentane
b. 3-ethyl-1,1-dimethylcyclopentane
c. 1-ethyl-3,3-dimethylcyclopentane
d. 4-ethyl-1,1-dimethylcyclopentane
2. The sp3 orbitals of a carbon in CH4 are formed from the following atomic orbitals:
a. 3, 2p orbitals
c. 2s and 2 of the 2p orbitals
b. 2s and 1 of the 2p orbitals
d. 2s and the 3 2p orbitals
3. Which of the following is not identical to the others?
A
C
B
D
a. A
b. B
c. C
d. D
4. Which of the following molecules would you expect to have a dipole moment?
I. CO2
II. HCN
III. CHCl3
a. II and III
b. only II
c. only III
d. I, II, and III
5. What is the dihedral (torsion) angle between the 2 bromine atoms in the following
Sawhorse projection?
Br
Br
H
a. 0°
b. 30°
CH3
H
CH3
c. 60°
d. 90°
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6. The correct IUPAC name for the following is:
a. 2,4,7-trimethylnonane
b. 3,6,8-trimethylnonane
c. 7-ethyl-2,4-dimethyloctane
d. 2-ethyl-5,7-dimethyloctane
7. Arrange the following isomeric alkanes in order of increasing boiling point.
I. n-heptane
II. 2,3-dimethylpentane
III. 2,2,3-trimethylbutane
a. I<II<III
b. II<III<I
c. III<I<II
d. III<II<I
8. Identify the relationship between the following Newman projections:
CH3
H3C
H
H
H
H3C
H
H3C
CH3
H
H
CH3
a. identical
b. different conformations
of the same compound
c. constitutional isomers
d. none of the above
9. The carbon–carbon single bond in the following molecule is formed by the overlap of
which 2 orbitals?
a. sp-sp
b. sp2-sp
H2C C C N
H
c. sp2-sp2
d. sp2-sp3
10. What is the IUPAC name of the compound shown in the following Newman projection?
CH3
H3C
CH(CH3)2
H
H
H
a. 1,2,3-trimethylbutane
b. 2,3-dimethylpentane
c. 2,3,4-dimethylpentane
d. 2-isopropylbutane
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True/False. Indicate whether the statement is true (T) or false (F). (2 pts each)
11. Hybrid structures show the most stable representation of a molecule.
12. Valence bond theory would predict 109.5° angles around each H–C–H bond in methane.
13. An alkane with less branching has a higher octane number.
14. Only electrons in π-bonds and lone pairs can move between two resonance structures.
15. sp2 hybridized orbitals have 1/3 ―s‖ character and 2/3 ―p‖ character.
16. The double-headed arrow between resonance structures indicates the equilibrium
between the two structures.
17. Hybridization is the only bonding model that can correctly predict bond angles around
atoms.
18. A sp hybridized carbon has 3 sp-orbitals and 1 unhybridized p-orbital.
19. Intramolecular forces must be overcome in order vaporize a substance.
20. At room temperature, the various conformations of butane do not interconvert; only the
anti form is present.
Short Answer.
21. Give two chemically-related examples where a change in molecular structure changes the
function of a molecule. (5 pts)
22. In one sentence, why do we use resonance structures? (5 pts)
23. Using resonance structures to support your answer, which compound has greater electron
density on its oxygen atom? (5 pts)
O
O
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Multi-part Questions. Make sure you read the entire question and answer all questions.
24. Fresh perspiration is odorless. The smell we associate with sweat is the result of bacteria
breaking down the components of perspiration, producing compounds with the
CH3
O
C
unappealing odors we associate with armpits and sweaty feet. One of the
C O
compounds responsible for such an odor is butanedione (right). For the
H3C
following questions, we are going to focus on the orbitals involved in the
bonding between carbon and oxygen in this compound.
C
O
a. Shade-in the orbitals that overlap to form the π-bond between the carbon and
oxygen in the figure above. (3 pts)
b. Draw in the lone pairs on oxygen in the correct orbitals in the figure above. (2 pt)
25. Lexapro® (right) is prescribed to treat depression and
general anxiety disorder. It works by increasing the amount
of the neurotransmitter, serotonin, between the neurons in
the brain.
a. For the atoms indicated, what is the geometry, bond
C
angle, and hybridization of each? Fill in the table
N
below. (9 pts)
Bond
Atom
Geometry
Hybridization
angle
C
O
N
F
A
N
B
O
b. Do rings A and B lie in the same plane? (3 pts)
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26. Use the potential energy diagram frame below to answer the following questions about
the rotation about the C-3—C-4 bond of 2-methylhexane.
a. Draw the Newman projection of the most stable conformer at the appropriate
energy level in the potential energy diagram. (2 pts)
b. Draw the Newman projection of the least stable conformer at the appropriate
energy level in the potential energy diagram. (2 pts)
c. What is the most specific term for the conformation of B? (1 pt)
d. What is the most specific term for the conformation of D? (1 pt)
e. Label the transition state from B to D on the energy diagram clearly. (2 pts)
f. Label the activation energy from B to D on the energy diagram clearly. (2 pts)
g. What type of strain is present in conformation A? What about B? (3 pts)
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27. a. Draw resonance structures for the following species including curvy arrows to show
electron flow from one resonance structure to the other. Rank the contributors (or
indicate they are equal) in order of decreasing contribution to the hybrid (most stable to
least stable). You do not need to include resonance forms that are so unstable that they
are not plausible. (5 pts)
CH2
C
H2C
CH3
b. Draw the hybrid structure of 27a. (3 pts)
c. Clearly label the longest carbon–carbon bond in structure 27a. (2 pt)
28. Which of the following is not a permissible contributing structure? Why? Using curvy
arrows, show electron movement that connects the two remaining structures. (5 pts)
H3C
O
OH
O
NH2
H2C
NH2
H3C
NH2
Bonus. Use resonance structures to determine which proton is more acidic (Ha or Hb). (Hint:
Draw the conjugate base for each.) (5 pts)
O
O
Ha
Hb
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