Midterm 3 2011 Solutions

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ORGANIC CHEMISTRY II (CHEM 324)
EXAM 3
April 19, 2011
There are six pages, TEN questions, and a total of 116 points in this exam, which gives an extra sixteen points on
top of that required for a “perfect” paper. Please read each question carefully and possibly more than once.
Good luck…
(20)
1.
Complete the following reactions. Give correct structures for the products formed.
O
1.1.
O
H
NH2
O
+
O
O
O
1.2.
O
N
O
O
NaOH (aq)
O
OH
OH
O
H2O - THF
O
CoA S
1.3.
+
HO
O
enzyme
N
N
O
(acetyl coenzyme A)
O
OH
O
1.4.
O
O
O
heat
HO
O
HO
O
O
O
OH
NaOCH2CH3
O
1.5.
OH
O
O
HOCH2CH3
O
O
C8H14O3
(5)
2.
Show all the possible enol (not enolate) forms of the molecule below:
O
O
OH O
OH O
O
OH
O
OH
Chem 324 Exam 3
B. Terem
(21)
3.
Circle the best correct answer (only ONE) for each of the multiple-choice questions below:
3.1.
Which of the following are derived from the Kiliani-Fischer (chain extension) Synthesis of the
same aldopentose?
H
H
HO
H
CHO
OH
OH
H
OH
CH2OH
H
HO
HO
H
(a)
(1) a and b
3.2.
CHO
OH
H
H
OH
CH2OH
H
HO
H
H
(b)
CHO
OH
H
OH
OH
CH2OH
(c)
(2) a and d
(3) b and c
HO
H
H
H
(d)
(4) b and d
CHO
H
OH
OH
OH
CH2OH
(e)
(5) b and e
What is the structure of the product formed following the dissociation of the tetrahedral
intermediate shown below?
HO
Cl
N
O
O
N
N
(1)
3.3.
CHO
H
OH
H
OH
CH2OH
HO
H
HO
H
O
Cl
(2)
OH
(3)
(4)
Which of the following is/are the pyranose form of D-galactose shown below?
H
HO
HO
H
CHO
OH
H
H
OH
CH2OH
galactose
OHOH
OH
(a)
(1) only (a)
OH
OH
(b)
(2) only (b)
(3) only (c)
Page 2
O
O
O
OH
HO OH
HO OH
HO OH
OH OH
O
OH
OH
OH
(c)
(4) both (a) and (c)
OH
OH
OH
(d)
(5) both (b) and (d)
Chem 324 Exam 3
B. Terem
3.4.
What is the structure of the reaction product below?
CN
1. CH3CH2MgBr
ether
2. H3O
O
HO
NH2
O
NH2
(1)
3.5.
(2)
(3)
(4)
What amine and carbonyl compound is needed to synthesize the enamine below??
N
O
H
N
NH2
(a)
(b)
(1) a and b
3.6.
(c)
(2) b and c
(d)
(3) a and d
(e)
(4) c and e
(5) a and e
Which of the following is no longer optically active upon being oxidized with HNO 3?
H
H
HO
H
CHO
OH
OH
H
OH
CH2OH
(1)
3.7.
O
O
H
HO
HO
H
CHO
OH
H
H
OH
CH2OH
H
HO
H
H
(2)
CHO
OH
H
OH
OH
CH2OH
(3)
HO
H
HO
H
CHO
H
OH
H
OH
CH2OH
HO
H
H
H
(4)
CHO
H
OH
OH
OH
CH2OH
(5)
Which of the following pair are identical after being treated with NaBH4 and worked up with
water?
HO
HO
H
H
CHO
H
H
OH
OH
CH2OH
(a)
(1) a and d
HO
HO
HO
H
CHO
H
H
H
OH
CH2OH
H
HO
HO
HO
(b)
(2) b and c
CHO
OH
H
H
H
CH2OH
HO
H
HO
H
(c)
(3) c and e
Page 3
CHO
H
OH
H
OH
CH2OH
HO
H
H
H
(d)
(4) b and e
CHO
H
OH
OH
OH
CH2OH
(e)
(5) c and d
Chem 324 Exam 3
B. Terem
(12)
4.
The multi-step synthesis shown may require temporary deactivation of a functional group. Design a
synthesis for the target molecule from the precursor shown. You may use any organic or inorganic reagents
and/or further precursors of your choice. Show all reagents and intermediate products formed.
O
H
HO
O
O
O
HO
OH
TsOH
O
O
O
O
O
LiAlH4
O
OH
H
OH
H3 O
O
(8)
5.
Give a detailed mechanism for the reaction below. Show the structure of the final product formed.
HO
H
HO
H
HCl (aq)
OH
OCH3
OCH3
H2 O
OH
OCH3
OCH3
O
OH
OCH3
OH
OCH3
H
OCH3
O
HO
O
OCH3
O
OCH3
HO
H
O
OCH3
O
H
O
H
HO
OCH3
O
OH
OCH3
Page 4
H
O
H
H
O
H
H
Chem 324 Exam 3
B. Terem
Question submitted by Cheryl
(7)
6.
Provide a “one-step” synthesis of the following alkene from the ketone shown. You can use any other
precursor of your choice as long as all precursors are neutral (non-ionic) to start with. For any charged
species or ylides you wish to use, you must show how they are prepared.
O
(C6H5)3P
CH2
BuLi
(C6H5)3P
CH3
(C6H5)3P
+ CH3Br
(18)
7.
The ketones shown below can all be synthesized starting from cyclohexa-1,3-dione (also given below) and
a different additional precursor for each case.
For each synthesis write the structure of the additional precursor in the boxes provided. Write also any
other reagent (acid, base, etc) needed.
Note that certain syntheses might require specific acids or bases; make sure to indicate these.
O
O
O
H
CH3CH2O-
O
O
O
O
LDA
O
O
O
O
O
O
O
Page 5
CH3CH2O-
Chem 324 Exam 3
B. Terem
(11)
8.
The tricyclic target molecule below can be synthesized from a bicyclic compound and another precursor
using Robinson Annulation methodology. Identify the structure of the bicyclic compound and the other
precursor. Identify also the structure of the precyclization intermediate.
H3CO
+
H3CO
O
O
O
H3CO
O
O
(10)
9.
The target molecule shown below can be prepared starting from only ONE of the following precursors:
either ethyl acetoacetate (“acetoacetic ester –AAE”) or diethyl malonate (“malonic ester –ME”), in a multistep synthesis. Choose either AAE or ME (write the full correct structure) –remember only one will workand show in detail the full synthesis. Give the structures of all the intermediate products; indicate all
reagents.
.
O
O
O
EtO
O
O
O
EtOH
Cl
O
O
O
O
O
O
O
HO
O
O
OH
heat
O
+
target molecule
(4)
10.
Name the following molecule according to the IUPAC rules:
O
O
Butyl benzoate
Page 6
CO2
O
OH
Chem 324 Exam 3
B. Terem
1
2
3
4
5
6
7
8
9
10
11
TOT
20
5
21
12
8
7
18
11
10
4
0
116
Page 7
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