Chem 332 Exam 4 May 22, 2010 Professor Fox 100 …Chem 332 Exam 4 May 22, 2010 Professor Fox 100...
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1 Chem 332 Exam 4 May 22, 2010 Professor Fox 100 points 180 minutes Your Name________________________________________
Transcript of Chem 332 Exam 4 May 22, 2010 Professor Fox 100 …Chem 332 Exam 4 May 22, 2010 Professor Fox 100...
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Chem 332Exam 4
May 22, 2010Professor Fox
100 points180 minutes
Your Name________________________________________
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Your Name________________________________________
2 points each
2 points each2. Circle the molecules that are aromatic.
HN
O
OO
NB
NBN
B
1. Provide reagents for the following transformations. There is no limit to the number of carbons that your reagents may contain.
NH2
O
NH2
O
O
OO
O
O
NC
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3. One of the steps in the following synthesis would not proceed in high yield. CIRCLE the problematic step, and describe the problem in the space below in 30 words or less
NH2O
O
= Merrifield resin
HO2C NHBoc
DCC, pyridineNHO
OO
NHBocF3CCO2H
O
NHO
OO
NH2
HO2C NHBocDCC, pyridine NHBoc
NHO
OO H
NNHBoc
O
NHBocF3CCO2H
O
NHO
OO H
NNH2
O
NH2
HO2C NHBoc
DCC, pyridine
NHO
OO H
N NHO
NH2
ONHBoc
F3CCO2H
ONHO
OO H
NNHO
NH2
ONH2
HF
NHO
HOO H
NNHO
NH2
ONH2
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a. Provide structures for B and C, and arrow pushing mechanisms for the formation of B, C andD. (6 pts)
b. Use molecular orbital theory to explain the stereoselectivity for the formation of B, C and D(12 pts)
You may use the next page to continue your answer
hν
A
ΔCB
Δ
D
4. Upon heating, compound A undergoes electrocyclization to isomeric compound B. Photochemical electrocyclization reaction of compound B produces isomer C. Finally, thermolysis of C produces isomeric compound D.
H
H
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4. (continued)
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15 pointsOH
HN
OBr
5. Provide a stereoselective synthesis starting with benzene and any other materials that contain three carbons or less. Any reagents that do not become incorporated into the product (e.g. PPh3) may contain more than three carbons
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Br
O
cat. Pd(0)Et3N
O
6. Provide a detailed arrow pushing mechanism.
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O
O OMe
NaH (a base)
NO2
OO
NO2
7. Provide a detailed arrow pushing mechanism.15 points
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6. Circle those sugars that give chiral diacids upon oxidation with HNO38 points
8. The unnatural sugar (L)-Altrose gives a diacid upon sequential Wohldegradation/HNO3 oxidation. Circle the naturally occuring (D)-sugar(s) that givethe same diacid upon sequential Wohl degradation/HNO3 oxidation.
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Your Name________________________________________3 points each
9. Identify each of the following pairs as being identical, meso, enantiomers, anomers, non-anomeric diasteromers. If none of these relationships apply, then indicate that the compounds are not stereoisomers.
O OH
OHHO
OH OHOOH
OHOHOH
OH(a)
(b)
(c)
identical (but not meso)
meso
enantiomers
anomers
diastereomers (but not anomers)
these compounds are not stereoisomers
H OH
FH OH
HHOOH
HH OH
OHF H
identical (but not meso)
meso
enantiomers
anomers
diastereomers (but not anomers)
these compounds are not stereoisomers
H3C OO
H3C
Leu-Tyr-Phe H3NHN
NH
CO2–
+ O
O
NOTE: the structures of the amino acids are on the following page
Ph
OH
identical (but not meso)
meso
enantiomers
anomers
diastereomers (but not anomers)
these compounds are not stereoisomers
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