351 Organic Chemistry II
Exam #1A, February 5, 2009
Winona State University
Professor T. Nalli
Name_____________________________ Section (circle one) 03 (T)
02 (W)
01 (Th)
General Instructions: Write your name in the space provided above and on the provided
Scan-tron form. Do not put your name anywhere else in this exam book.
Make sure that you read each question carefully and provide complete answers. Time
limit is 55 min. Exams must be turned in immediately upon my call of time up.
Grading: Grading will be on the basis of a highest possible score of 100 points.
I. Multiple Choice – 2 points each, 30 points total
II. Nomenclature/Structure – 2.5 points each, 10 points total
III. Resonance Structures – 2.5 points each, 15 points total
IV. Reaction Products – 5 points each, 40 points total
V. Mechanism Problem – 5 points
1
I. Multiple Choice
Use the following choices for questions 1-5.
A.
B.
C.
D.
1.
Which diene gives off the least heat when combusted in a bomb calorimeter?
2.
Which compound has an sp-hybridized carbon atom?
3.
Which compound is conjugated?
4.
Which compound is the most reactive toward air oxidation via a free-radical chain reaction?
5.
Which compound possesses the shortest C-C single bond?
6.
Which of these reagents is not commonly used as an oxidizing agent?
A. H2SO4
B. K2Cr2O7
C. NaOCl
D. OsO4
7.
Which statement is true about free-radical halogenation reactions?
A. Chlorination is less selective than bromination because Cl atoms are more reactive than Br atoms.
B. Chlorination is less selective than bromination because Cl atoms are less reactive than Br atoms.
C. Chlorination is more selective than bromination because Cl atoms are more reactive than Br atoms.
D. Chlorination is more selective than bromination because Cl atoms are less reactive than Br atoms.
8.
Which of the following is a chain propagation step in the free-radical chlorination of methane?
A. Cl• + •CH3  CH3Cl
B. •CH3 + CH4  CH4 + •CH3
C. Cl2  2 Cl•
D. CH4 + Cl•  •CH3 + HCl
9.
Which compound is most likely to function as a free-radical scavenger?
OH
Cl
OH
A.
10.
B.
C.
D.
Which of the following radicals is the most stable? (Consider all resonance structures of each!)
A.
B.
C.
D.
2
11.
How many total different constitutional isomers are formed as products in the monochlorination of
2-methylpentane as shown below? (Do not count enantiomers!)
Cl2
C6H13Cl
UV light
A. 3
B. 4
C. 5
D. 6
12.
At room temperature, chlorine atoms react 5.5 times faster with tertiary hydrogens than they do
with primary Hs. What percentage of the major product is formed in the room temperature
chlorination of 2-methylpropane?
A. 38%
B. 52%
C. 62%
D. 71%
13.
Which of these radicals is the most stable?
A. n-butyl
B. tert-butyl
C. isobutyl
D. sec-butyl
14.
The organic starting material undergoes reduction in all of the following reactions except one. In
which reaction is the organic substrate not reduced?
15.
Which sequence of reactions represents the best synthesis of meso-5,6-decanediol from 5-decyne?
OH
?
OH
A. 1. H2, Pd-Lindlar
B. 1. Na, NH3
C. 1. H2, Pd-Lindlar
D. 1. NaNH2
-
2. KMnO4, OH
2. KMnO4, OH2. CH3CO3H
2. KMnO4, OH-
3. H2O, H+
3
II. (a) Draw the structure of each of the following.
1. NBS
2. mCPBA
3. PCC
4. polyethylene
III. Show all significant resonance structures for each of the following structures. If none exist (i.e., the
molecule is not conjugated), write “none exist”.
OH
N
1.
4.
O
NH2
2.
5.
O
N
3.
H
6.
4
H
IV. Give the structure of the main organic product of reactions 1-8 below. If no reaction occurs write
“n.r.” and explain why.
CHCH2CH3
mCPBA
1.
2.
HCl (1 equiv)
o
-78 C
3.
HCl (1 equiv)
o
40 C
Br2
4.
UV light
NBS
h
5.
7.
8.
CrO 3
OH
6.
H2SO4, H2O
O3
C C
OH
H2O
PCC
5
V. Write out the mechanism of the reaction shown below. Use curved arrows or curved half-headed
arrows (fishhooks) to show electron flow as appropriate.
Br
HBr
ROOR
6