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Organic Chemistry I Test 3 Extra Synthesis Practice Problems Page 1: Synthesis Design Practice. Practice. Page 2+3: Predict the Product Practice (including some that involve stereochemistry). Page 4: Cis/trans Stereospecific Stereospecific reactions: which recipe to use; which E or Z alkene to use. Page 5: Recognizing cationic/anionic/radical reactions, and reasonable intermediates/first intermediates/first steps Page 6: Elements of unsaturation/hydrogenation unsaturation/hydrogenation problems; ozonolysis puzzle problems. A. Provide reagents for the following transformations. transformations. Br
OH
Br
1.
O
OH
2.
Cl
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3.
4.
Br
OH
HO
Br
Br
OH
OH
5.
O
T O
6.
HO
7.
HO
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B. Draw the major product for each of the following reactions or reaction sequences. You needn’t bother
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to show side products or minor products. For chiral molecules that are racemic , you needn’t draw both enantiomers. BE CAREFUL TO SHOW THE CORRECT ORIENTATION, AND THE CORRECT STEREOCHEMISTRY IN CASES WHERE STEREOCHEM IS FACTOR. (3 points each). H 2SO4, heat
OH
8. Br
NaOH
9. Br
NEt 3
10. HBr
11. HBr, peroxides T
12. 1. HBr, peroxides
13.
2. NaOCH 3 H 2O, H+
14. 1. Hg(OAc) 2, H 2O
15.
2. NaBH 4 1. Hg(OAc) 2, H 2O
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2. NaBH 4 3. H 2SO4 1. BH 3-THF
17.
2. NaOH, H2O2 1. BH 3-THF
18. 19.
2. NaOH, H 2O2
1. Hg(OAc) 2, CH 3OH 2. NaBH 4
Note: explicit stereochemistry must be drawn. The enantiomer would have been equally acceptable.
$ 1. HBr 2. NaOCH 3
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Br 2
21.
Br 2, H 2O
22. Br 2
23. Br 2, H 2O
24. Cl2
25. Cl 2
26. PhCO3H
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27. PhCO3H
28.
Ph
CH3CO3H, H 2O
29.
Ph CH 3CO 3H, H 2O
30. OsO4, H 2O2
31.
Ph OsO4, H 2O2
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32. 1. O3 2. Me 2S
33. 1. O 3
34.
2. Me 2S
Note: explicit stereochemistry must be drawn. The enantiomer would have been equally acceptable. This principle will apply for any of the reactions producing two chiral centers. Problems 23-32
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C. Draw the alkene that would product the products shown. Make sure to make your drawing clear whether the starting alkene was E or Z. Cl
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Cl 2
Ph Cl
35.
OH
Br 2, H 2O
Br
36.
OH
CH 3CO 3H, H 2O
OH
37.
OH OsO4, H 2O2 OH
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1. BH 3-THF
H 3C H
2. NaOH, H 2O2
Ph OH
39. O
PhCO 3H H 3C
40.
CH2CH3
1. O3 2. Me 2S
41.
D. What reagent(s) would you use to conduct the following transformations? T
OH Ph
Ph OH
42. CH 3 Ph
43.
H 3C OH Ph OH
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E. Recognizing whether reaction mechanisms should be cationic, anionic, or radical; whether intermediates should be cationic, anionic, or radical; and recognizing what could be reasonably involved in the initial reaction step. T
44. The transformation shown is common in many biological systems. Which of the following statements is definitely, absolutely false? a. The first step in the mechanism probably involves protonation of the carbonyl oxygen. b. The overall reaction involves an addition reaction c. The mechanism is probably radical in nature 45. For the transformation shown, which of the following statements is definitely, absolutely false? a. The first step in the mechanism probably involves protonation of a carbonyl oxygen. b. The overall reaction involves a substitution reaction c. The mechanism is probably anionic in nature d. The first step in the mechanism involves ethoxide anion grabbing a hydrogen.
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46. Shown is a reaction, and some possible intermediates along the mechanistic pathway. Given the reaction conditions shown, which of the following statements is true? a. Structures A and B might be plausible intermediates; structure C definitely isn’t b. Structures A and C might be plausible intermediates; structure B definitely isn’t c. Structures B and C might be plausible intermediates; structure A definitely isn’t d. Structure A might be a plausible intermediates; structures B and C definitely aren’t 47. Shown is a reaction, and some possible intermediates along the mechanistic pathway. Given the reaction conditions shown, which of the following statements is true? a. Structures A and B might be plausible intermediates; structure C definitely isn’t b. Structures A and C might be plausible intermediates; structure B definitely isn’t c. Structures B and C might be plausible intermediates; structure A definitely isn’t d. Structure A might be a plausible intermediates; structures B and C definitely aren’t
OH
O H+ HO
O
H2O
O
O
O
1. NaOEt
OEt
OH
OEt
2. BrCH3
CH 3
O
H+ H2O
NMe2
O
+ HNMe 2 H
OH
O
A
NMe 2
NMe 2
B
O Ph
OH
C
H
O
NaOMe
OCH3
O
Ph
MeOH
OCH3 Ph
O Ph A
OH OCH3
Ph B
OCH3
H 3CO O O Ph C
Ph
OCH3
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F. Elements of Unsaturation/Hydrogenation Problems. For each problem there will be multiple satisfactory solutions. T
48. Provide a possible structure for a compound with formula C5H8, given that it reacts with excess H2/Pt to give C5H10.
Answer must show one alkene and one ring. (Other structures also meet that requirement). H2/Pt test proved 1 alkene. EU=2 originally. So the other EU must be ring.
49. Provide a possible structure for a compound with formula C6H8, given that it reacts with excess H2/Pt to give C6H12.
Answer must show two alkene and one ring. (Other structures also meet that requirement). H2/Pt test proved 2 alkenes. EU=3 originally. So the other EU must be ring.
50. Provide a possible structure for a compound with formula C8H10, given that it reacts with excess H2/Pt to give C8H14.
Answer must show two alkenes and two rings. (Other structures also meet that requirement). H2/Pt test proved 2 alkene. EU=4 originally. So the other two EU must be two rings.
51. Provide a possible structure for a compound with formula C6H8, given that it reacts with excess H2/Pt to give C6H12.
Answer must show two alkene and one ring. (Other structures also meet that requirement). H2/Pt test proved 2 alkenes. EU=3 originally. So the other EU must be ring.
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G. Ozonolysis: Draw starting chemicals that will undergo ozonolysis to produce the products shown. In some cases there may be more than one satisfactory answer. 1. O 3
52.
O H
2. Me 2S
O
O
H
1. O 3 2. Me 2S H O
53.
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Any of three answers
O
1. O 3 H 2. Me 2S
H O
H
54.
H
1. O 3
55.
2. Me 2S
O +
O
O
O
+ H
H
O
+ H
O
