CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
1. Concepts
a. Draw the remaining resonance structures for the following radicals.
b. Balance each equation, then indicate which direction is favored by writing “LEFT” or
“RIGHT” above the equilibrium arrow.
SiCl4
+
4 CH3MgCl
TiCl4
+
2 CH3ZnCH3
CH3CH2CH2Li
+
PdCl2
RIGHT
LEFT
RIGHT
1
(CH3)4Si
+
4 MgCl2
(CH3)4Ti
+
2 ZnCl2
CH3CH2CH2PdCl
+
LiCl
CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
2. Reactions
a. Draw the major product or products of each of reaction in the boxes provided. If multiple
organic products are equally likely, show each. For stereoselective reactions, be certain that your
structures clearly indicate stereochemistry.
Cl
ClMg
Mg
HBr, ROOR
Br
Br
Br2, h
MgBr
1) CH3CH2CH2I
2) H3O+
Br
+
NBS
Br
2
CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
CH3
Li, NH3 (liq)
CH3
C
C
CH3
H
C
C
H
CH3
ZnBr2
ZnBr
Li
O
OH
1) CH3CH2Li
2) H3O+
CH3
CH3
1) (CH3CH2)2CuLi
2) H3O+
CH2CH3
Cl
SnCl2 (0.5 equiv)
Li
3
Sn
CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
3. Mechanism
Draw a complete arrow pushing mechanism for the following reaction.
CH3
C
C
Li, NH3 (liq)
CH2CH3
Li
Li
CH3
C
C
H
CH3
CH2CH3
C
C
CH2CH3
N
H
H
H
CH3
C
C
H
H
H
CH2CH3
Li
CH3
N
C
C
CH2CH3
Li
Li
H
CH3
C
C
N
H
H
H
CH2CH3
Li
N
H
H
4
H
CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
4. Synthesis
Propose a selective multi-step synthesis of each target molecule starting with the compound
provided. Show the necessary reagents and products for each step.
a.
Br
Br
CH3CH2O
Br2, h
Br
Br2
Br
Br
b.
OH
Br
Br
1) (CH3)2CHLi
Br2, h
+
2) H3O
Br
OH
H2O
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CHEM 302 - Dr. Hartel
Winthrop University
Self Evaluation 1
5. Application of Concepts
a. As you learned in class, peroxides are an excellent source of radicals used to initiate radical
chain reactions. One variation is the use of acyl peroxides, an example of which is shown below.
Propose a complete arrow-pushing mechanism (two step) for the formation of methyl radical
from diacetyl peroxide. What is the other product formed in the reaction? Carbon dioxide.
O
C
CH3
O
O
CH3
C
O
Diacetyl peroxide
CH3
O
O
C
C
O
O
CH3
CH3
C
O
CH3
C
+
O
O
O
O
O
CH3
C
C
O
O
+
CH3
b. Consider the following metallation-transmetallation reaction sequence shown below. A
possible side reaction for this preparation is the formation of 2,3-dimethylbutane. Thoroughly
explain how you could use 1H-NMR to determine if the reaction proceeded to the desired
product, the undesired product of the side reaction, or was simply unreacted 2-bromopropane.
1) Li
Br
2) SiCl4 (0.25 equiv)
Si
Si
Br
A
B
C
The simplest way to distinguish the three compounds would be to compare the chemical shift of the secondary
carbon on each. In A, this carbon is deshielded by the electronegative bromine, forcing the hydrogen bonded to it to
resonate at higher frequency (downfield). In B, the secondary carbon is quite generic, and the hydrogen bonded to it
would be just a typical alkyl carbon (1-2 ppm). In C, the secondary carbon is bonded to a silicon, which is less
electronegative than the carbon, which acts to shield the carbon and thus the hydrogen bonded to it would show up at
a rather low frequency (upfield).
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