CHE 230 Organic Chemistry
Exam 2, March 8, 2000
Name
Student ID No.
Before you begin this exam: First: You are allowed to have a simple model set at
your seat. Please put away all other materials. Second: Place your student
identification on your desk. A proctor will come around to check everyone’s ID.
Third: Read through the entire exam. Your goal, as always, is to score as many
points as possible. Do not waste time on problems that you can’t do if there are
others that look easy. Fourth: It is critically important that your answers be written
in a clear, unambiguous manner. Answers in which your intentions are unclear
will not receive credit. Fifth: READ THE INSTRUCTIONS FOR EACH PROBLEM.
If you wish to have your exam score posted beside your student ID number in the
.
glass case (behind CP-139) with the exam key, place an ‘X’ in this space
If you do not mark this space, your exam score will not be posted.
You have until 9:50 to complete this exam. There will be no extensions, so budget
your time carefully.
Problem Number
1.
Points possible
Score
15
2.
14
3.
8
4.
5
5.
12
6.
22
7.
15
8.
9
Total
100
1
1.
(15 points) Classify the relationship between each pair of structures as either
skeletal isomers, conformational isomers, enantiomers, or diastereomers.
a)
CH3
Cl
Cl
CH3
Conformational isomers
b)
Cl
Cl
Enantiomers
c)
Cl
Cl
Cl
Cl
Diastereomers
d)
OH
CHO
H
OH
HOCH2
CHO
H
OH
OH
CH2OH
Diastereomers
e)
Skeletal Isomers
2
2.
(14 points) Assign the R, S convention to the indicated stereogenic centers
and assign the E, Z convention to the indicated C=C bonds.
a)
R
O
CH3
N
N
R
CH3
NH
Lysergic Acid Diethylamide (LSD)
b)
R
Z
O
R
CO2H
HO
E
HO
S
Prostaglandin E2
3
3.
(8 points) Classify each of the following compounds as either chiral or
achiral.
a)
N
N
CHIRAL
Nicotine
b)
O
P
N
F
S
CH3
CHIRAL
VX, the most potent nerve gas in the US arsenal
c)
CO2H
O
O
CH3
ACHIRAL
o-Acetylsalicylic acid (aka Aspirin)
d)
O2N
NO2
N
N
N
NO2
ACHIRAL
HMX (“Her Majesty’s Explosive”)
4
4.
(5 points) Which one of the structures below is the meso isomer of 2,3dihydroxybutane? (Circle it)
OH
OH
OH
5.
OH
(12 points) Draw a Newman projection of the most stable conformation of
each of the following compounds:
a) cis-1,3-dichlorocyclohexane
H
H
H
H
H 3C
CH3
H
H
b) 2-methylbutane
CH3
H3C
H
H
CH3
H
c) trans-4-bromo-methylcyclohexane
H
H
H
Br
H 3C
H
H
H
5
6.
Newman projections I - VI of (meso)-3,4-dimethylhexane are shown below.
All of these are sighting down the C3-C4 bond.
a) (5 points) Which one of the eclipsed conformations is of the highest
energy? (Circle it)
H
H
CH3
CH3
CH
H 3
CH2CH3
CH2CH3
H3CH2CCH
III
HCH2CH3
CH2CH3
H
3
HCH
3
CH2CH3
CH3
III
b) (5 points) Which one of the staggered conformations is of the lowest
energy? (Circle it)
H
CH2CH3
CH3
CH2CH3
CH3
CH3
H
CH3
IV
H
H
H
CH3
CH3CH2
CH2CH3
CH2CH3
CH3
V
CH2CH3
H
VI
c) (12 points) Draw a rotational energy diagram for 360 degree rotation
around the C3-C4 bond of (meso)-3,4-dimethylhexane. Your energy diagram
should clearly indicate the relative energies of conformations I - VI. A
starting point (conformation IV) has been provided.
I
II
E
III
V
IV
VI
θ
6
7.
(15 points) Draw each of the following cyclohexane derivatives in their most
stable chair conformation.
a)
b)
c)
H
H
7
8.
(9 points) How many stereoisomers are there of each of the compounds
shown below? (NOTE: this question does not ask for the maximum number
possible. You are to determine how many stereoisomers can be drawn for
each compound)
a)
CH3
CH3
3
b)
4
c) (careful with this one....)
CH3
2
END OF EXAM
8