Chemistry 216
First Examination
March 15th, 2005
Professor John Nanos
(1.5 hr, 88 points)
Name____________________
Please print
Signature _______________________
Student ID # _____________________
Please CHECK OFF your lab section.
(minus 3 points for no check)
Monday _____110
_____111
_____112
_____113
_____310
_____311
_____312
Wednes- _____150
day
_____151
_____152
_____153
_____154
_____351
_____352
_____353
_____354
Thursday _____170
_____171
_____172
_____370
_____371
_____372
_____373
_____374
_____375
_____376
Todd Senecal
Tuesday _____130
Eric Wiedner
_____131
Josephine Nakhla
_____132
Jonathon Fritz
_____133
Marisa MacNaughyan
_____134
Mike Purkey
_____330
Joseph Hunt
_____331
_____332
_____333
Gayle Gawlik
_____334
Tara Conser
Eric Wiedner
Todd Groendyke
William Lai
Marisa Mac.
1
Brian Brennon
Greg Less
2
Josephine Nakhla
Lothar Steffens
Christine Nguyen
Geoff Halvorsen
Jun Pan
Jinhui Chen
Greg Less
Todd Groendyke
Tara Conser
Jonathon Fritz
Tony Wildon
Lothar Steffens
Christine Nguyen
Geoff Halvorsen
Brian Brennon
William Lai
Jun Pan
Joseph Hunt
Tony Wildon
Gayle Gawlik
Jinhui Chen
06
05
3
10
4
09
5
12
6
12
7
03
8
09
9
10
10
12
TOTAL
88
Page 2. Chem. 216 Winter 2005
Name:________________________
I. (6 Points)
Arrange the following bithiazole derivatives in order of their relative Rf values when analyzed by
TLC on silica coated plates using a 3/1 ethyl acetate to hexane developing solvent system.
H3C(H2C)8
H3C(H2C)8
O
N
S
H
OH
S
N
N
O
(CH2)8CH3
A
S
HO
OH
S
O
N
(CH2)8CH3
B
H3C(H2C)8
N
S
H
S
H3C(H2C)8
H
N
S
N
C
H
(CH2)8CH3
S
D
<
Lowest Rf
<
OH
N
<
(CH2)8CH3
3pts
Highest Rf
If compound C gave an Rf of 0.95 using the solvent system stated above, give a brief
suggestion of the step(s) necessary to yield a more acceptable Rf value.
2pts
What technique would you use to observe the spots on the TLC plate?
1pt
Page 3. Chem. 216 Winter 2005
Name:________________________
II. (5 Points)
Solubility
3pts
Temperature (C)
Too good, Too bad, and Ideal. These are three possible categories for recrystallization solvents
we have encountered in our experiments when trying to purify a solid product. Draw and label
the three solubility curves on the graph above for each of these scenarios.
It is often very difficult to find a particular solvent that follows the ideal curve. Give a single
sentence suggestion of what you could do in this case to achieve the ideal recrystallization
condition.
2pts
III. (10 Points)
Provide a detailed, step-wise mechanism using curved arrow notation for the acid catalyzed
shown below. You may use HB and B:- to denote Bronsted acid and its conjugate base as needed.
Do not add any other reagents. In the box provide, state the name of this type of reaction.
O
O
Strong Acid
Catalyst
HO
H-B (start here)
O
OCH2CH3
+
HOCH2CH3
Reaction Name (1pt):
9
Page 4. Chem. 216 Winter 2005
Name:________________________
IV. (9 Points) Show ALL calculations.
O
monomer
N
EtOH
2
+
CH2Br
S
∆
A
H
B
B
S
Note: Atomic weights chart H C O N S Br Li
1 12 16 14 32 80 7
N
0. 5
H
S
S
N
E - dimer
N
S
S
N
H
H
C N
1.1 eq. n-BuLi
CuCl2
Li+
N
-
S
S
D
H
+
N
IV A. The preparation of C from the reaction of A and B proceeds in an 50% yield.
What is the mass (mg) of A and B required to prepare 252mg of C?
IV B. Compound C reacts with n-Butyl lithium (n-BuLi) [as described in the scheme above] at -67C to
form the mono-lithium salt of C. If we used all 252mg of C formed in the previous question, how many
milliliters (mL) of a 0.55M solution of n-BuLi in hexane would be required to produce compound D?
IV C. Compound D is a reactive intermediate and is not isolated. After D is generated from C, D is
immediately oxidatively coupled with CuCl2 to form the dimer, E. If we start with 252mg C and we
obtain 100mg of E, what is the yield of the reaction going from monomer to dimer?
Page 5. Chem. 216 Winter 2005
Name:________________________
V. (12 Points) For each of the following synthetic reactions, draw the structure of the expected products
or reagents in the box provided.
O
O
(1)
NH2
O
Excess
H2O (solvent)
H2N
Water Soluble
3pts
Hint:
Two different
υ C=O stretches
(1710 and 1730 cm-1)
OH
(2)
Excess PCC
OH
CH 2Cl 2
CH3
3pts
3pts
O
(3)
O
OH
HO
H2SO4
(catalyst)
+ Excess
OH
O
3pts
Page 6. Chem. 216 Winter 2005
Name:________________________
VI. (12 Points) Compound A reacts with NaBH4 to yield three products. Draw the structure of each
of the three products and indicate (write “major” in the upper right hand portion of the box ) which of the
three is the major product formed. Also, give a brief explanation as to why this is produced in a higher
relative proportion than the other two. LiAlH4 also reacts with A, but in an entirely different manner
than the NaBH4. Give the two products that would form using this reagent
Explanation:
2pts
+ EtOH
2pts
2pts
2pts
NaBH4
EtOH, RT
O
A
O
O
THF
1. LiAlH4
2. NH4Cl(aq)
Cis
Trans
+ EtOH
2pts
2pts
Page 7. Chem. 216 Winter 2005
Name:________________________
VII. (3 Points)
Give a brief explanation of what is wrong, if anything, with the liquid IR spectrum
depicted below and how would you correct the problem. If nothing is wrong, just state that.
Wavenembers (cm-1)
3
VIII. (9 Points) For each of the following sets of compounds, match each compound to its expected
IR frequency for the C=O bond stretching absorption and provide a brief explanation to justify your
answer. If your explanation involved the resonance concept, be sure to draw relevant resonance
Structures and if your explanation includes the inductive effect, make sure to indicate which direction
electrons move inductively.
1666, 1687, 1703 cm-1
..
H3CO
..
S
O
:O :
+
N
S
O
:..O:-
S
O
Page 8. Chem. 216 Winter 2005
Name:________________________
IX. (10 Points)
NaOH (1 eq.)
Cl
+
S
O
A
H
O
EtOH, room Temp.
O
B
2pts
Provide in the box below, a step-by-step base catalyzed mechanism, through the use of the curve
arrow convention, for the formation of the product from the reaction of A and B in the presence
of a base. Circle the rate limiting step of the mechanism.
8pts
Page 9. Chem. 216 Winter 2005
Name:________________________
X. (12 Points) The table below lists the structures of a number of organic molecules. On pages 10-12
are infrared (IR) spectra for six compounds. The compounds are among those structures given in the
Table below. Assign each spectrum to its corresponding compound by putting the associated letter in
the answer box below each spectrum. The tables of characteristic IR frequencies appear on pages
13 and 14.
A
OH
OH
G
O
O
B
O
H
H2N
O
O
C
I
O
H2N
O
O
CH3
D
H3C
C
H2
O
O
J
O
O
O
E
O
O
K H3C
CH3
O
N
H
L
F
OH
O
C
H2
O
Page 10. Chem. 216 Winter 2005
Name:________________________
X. (Continued)
1.
Answer
Wavenumbers
%T
2.
Answer
Page 11. Chem. 216 Winter 2005
X. (Continued)
3.
4.
Answer
Answer
Name:________________________
Page 12. Chem. 216 Winter 2005
X. (Continued)
5.
Answer
6.
Answer
Name:________________________
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Scribble Sheet