CHEM 241-Davis
Organic Chemistry
Examination 3
December 7, 2010
YOUR NAME
(Last, First)
__________________________
Initial of Last Name
1
CHEM 241-Davis, Examination 3
YOUR NAME
__________________________
(Last, First)
University Honor Code Acknowledgment
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Signature
• This exam is worth 100 points
Notes
• There are 7 Problems on pages 3-9. Make sure your exam has all the pages.
• Nothing written on page 10 will be graded-this is for scratch work
• The exam period is for 75 minutes (9:30-10:45 am).
Points
Problem 1
(15)
Problem 2
(10)
Problem 3
(15)
Problem 4
(15)
Problem 5
(15)
Problem 6
(15)
Problem 7
(15)
Total
(100)
2
Question 1. Usually enol tautomers are less stable than their keto tautomers, as exemplified by
the Keq value of 10-4 for cyclohexanone. However, enol 2 tautomer is greatly favored over
cyclohexadienone 1 (Keq= 106). (15 pts)
O
OH
Keq= [enol]/[keto]= 10-4
O
OH
1
4
1
What is the common name for compound 2?
2
3
Keq= 106
2
_________________________
(3 pts)
What one word explains why enol 2 is favored over ketone 1? ________________ (3 pts)
Is the following statement true or false? The C1-C2 distance in 2 is shorter than the
C2-C3 distance in 2.
Circle the answer
TRUE
FALSE
(3 pts)
Draw a step-wise mechanism for the isomerization of ketone 1 to enol 2. Assume that the
reaction occurs in water (6 pts)
3
Question 2 (10 pts).
a) Circle the compound in each pair of dienes that reacts faster in a Diels-Alder reaction. (6 pts)
CH2
NH
CH2
CH3
CH3
CH3
H3C
b) Draw structures for diene 1 and dienophile 2 that are needed to form the product 3. (4 pts)
CO2Et
+
CO2Et
3
1
2
4
Question 3. (15 pts)
a) For each of the following 5 species, circle the best answer indicating whether that species is
aromatic or non-aromatic. (10 pts)
Aromatic
Non-Aromatic
Aromatic
Non-Aromatic
Aromatic
Non-Aromatic
Aromatic
Non-Aromatic
Aromatic
Non-Aromatic
N
H
_
H
+
H
b) Circle the compound that has the most acidic C(sp3)-H proton. (5 pts)
O
5
Question 4. (15 pts)
a) Indicate the structure of the major product in the following 3 reactions. (9 pts)
Br2
H3C
OCH3
FeBr3
Br2
H3C
NO2
FeBr3
Br2
H3C
NO2
FeBr3
b) Illustrate with structures the role of the FeBr3 in the above reactions. You only need to show
how FeBr3 activates Br2 for subsequent reaction with an aromatic ring. Draw all the electron
pairs and any formal charges on atoms. (6 pts)
6
Question 5. Write a mechanism for this transformation. (15 pts)
7
Question 6. Provide structures for compounds 3-5 and for the reagents necessary to
convert 1 to 2 and 5 to 6. (15 pts) Hint: Compound 5 is an α-amino acid formed in the socalled Strecker synthesis.
O
Zn/Hg
HCl
1
2
3
O
H
AlCl3
Cl
1) NH3, HCN
2) H3O+, heat
5
4
O
H3CO
NH2
6
8
Question 7. Provide a stepwise mechanism that explains the formation of the major product 3 in
the reaction of benzene with 1-chloro-2-methyl-propane. (15 pts)
CH3
H3C
Cl
CH3
H3C
1
AlCl3 (cat)
CH3
CH3
+
H3C
2
Minor
3
Major
9
BLANK PAGE FOR SCRATCH WORK-NOTHING WILL BE GRADED ON THIS PAGE
10