CHE 230 - Organic Chemistry
Exam 2, March 6, 2002
Name KEY
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. You have
until 9:50 to complete this exam. There will be no extensions, so budget your time carefully.
If you wish to have your exam score posted beside your student ID number in the glass case (1st
floor, CP Building, 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.
Problem
Points
1.
6
2.
8
3.
8
4.
9
5.
10
6.
9
7.
15
8.
15
9.
10
10.
10
Total
100
Score
1
1.
(6 points) Circle the chiral compounds among those listed below.
O
O
OH
NH
H
Cinnamaldehyde
Menthol
Caprolactam
(a component in Nylon)
CO2H
O
O
CO2H
CH3
Ibuprofen
Aspirin
2.
(8 points) Draw the structure the following compounds. Be sure to clearly indicate the
stereochemistry.
a)
R –2-chlorobutane
Cl
b)
trans-1-Bromo-3-chlorocyclobutane
Br
Cl
2
3.
(8 points) Assign the configuration at all stereogenic centers in the following compounds
using the R,S convention.
a)
CH3
CH3CH2
Br
H
s
b)
CH3
CH2 Br
R and R
c)
O
OH
H3C
H
4.
OH
R
(9 points) What is the relationship between the structures shown? Classify each pair as
either enantiomers, diastereomers, or conformational isomers.
a)
CH3
H
Br
Br
Br
H
Br
CH3
Diastereomers
b)
H
H
H
H
CH3
H
CH3
H
CH3
H
H
H
H
H
CH3
H
Diastereomers
3
c)
O
OH
OH
H
OH
5.
O
OH
OH
H
OH
OH
OH
Diastereomers
(10 points) Draw the following compounds in the MOST STABLE chair conformation.
Be sure that the direction of bonds (axial or equatorial) is easy to determine from your
drawing.
a)
CH3
CH3
CH3
CH3
CH
CH3 3
CH3
H
H
CH3
b)
HOCH 2
O
HO
OH
HO
HO
OH
OH
CH2OH
O
OH
OH
(b-D-glucose)
6.
(9 points) How many stereoisomers are there of the following structures?
a)
HOCH 2
O
OH
OH
8
b)
OH
OH
3
4
c)
OH
8
Careful with this one. Remember what “stereoisomer” means…..
7.
(15 points) Provide the expected organic product for each of the reactions below.
a)
NaI
H
CH3CN
Br
I
H
Note: Show the stereochemistry of the product
b)
NaCN
OTs
CN
CH3CN
c)
OH
CH3O
OTs
TsCl, pyridine
CH3O
5
8.
(15 points) Provide reagents that will bring about the conversion of the chloride shown
into the products shown. You are expected to provide “complete” reagents: if you wish
to use bromide as a nucleophile, specify a reagent such as LiBr, don’t write just “Br-“.
NaI
Cl
I
NaSCH3
SCH3
CN
NaCN
9.
(10 points) In your text it is pointed out that the substitution reaction below is
intermolecular (bimolecular) rather than intramolecular (unimolecular). The author
suggests that you think about the geometry transition state for the intramolecular process.
IN THE SPACE PROVIDED, explain why the transition state for the intramolecular
process is unfavorable. Note: a picture is worth 1,000 words….
O
O
O
CH
CH 3
OTs
O
S
S
O
O
CH CH3
OTs
The nucleophile cannot attack into the s* orbital. The ring constrains the conformational
mobility, so that the nucleophile can not approach on-line with s*.
O
H C H
H
OTs
6
10.
(10 points) Draw a viable mechanism for the reaction below. Be sure to use arrows
properly! Your mechanism must show the formation of all three products.
OTs
H2O, heat
H3O
HO
OTs
OTs
+ OTs
H
O
H
H
O
H
O
H
H
O
H
7
END OF EXAM
8