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Organic Chemistry practise

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Organic Chemistry I
Test 3
Extra Synthesis Practice Problems
Page 1: Synthesis Design Practice.
Page 2+3: Predict the Product Practice (including some that involve stereochemistry).
Page 4: Cis/trans Stereospecific reactions: which recipe to use; which E or Z alkene to use.
Page 5: Recognizing cationic/anionic/radical reactions, and reasonable intermediates/first steps
Page 6: Elements of unsaturation/hydrogenation problems; ozonolysis puzzle problems.
A. Provide reagents for the following transformations.
Br

OH

1.

Br


O

OH

2.

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Cl

3.

Br

4.

Br

OH

HO

Br

OH

5.

OH

O

T

6.

O

HO

7.

HO

1
 



 
2
 
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 2SO 4, heat

8.

OH
Br

NaOH

9.
Br

NEt 3

10.
HBr

11.
HBr, peroxides

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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

16.
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2. NaBH 4
3. H 2SO 4
1. BH 3-THF

17.

2. NaOH, H 2O2
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.



 

3
 
1. HBr
2. NaOCH 3

20.
T

Br 2

21.

Br 2, H 2O

22.

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

Br 2

23.
Br 2, H 2O

24.
Cl2

25.
Cl2

26.

PhCO 3H

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27.
PhCO 3H

28.

Ph

29.

Ph

CH 3CO 3H, H 2O

CH 3CO 3H, H 2O

30.
OsO4, H 2O2

31.

Ph

OsO4, H 2O2

T

32.
1. O3

33.

2. Me 2S
1. O3

34.

 

2. Me 2S


 



 
4
 
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

T

Cl2

Ph

35.

Cl

OH

Br 2, H 2O

36.

Br

OH

CH 3CO 3H, H 2O

37.

OH
OH
OsO4, H 2O2

38.

OH

T

1. BH 3-THF

H 3C H

2. NaOH, H 2O2

Ph

39.

OH

O

PhCO 3H
H 3C

40.

CH2CH 3

1. O3
2. Me 2S

41.

D. What reagent(s) would you use to conduct the following transformations?
T

OH
Ph

Ph

42.

OH
CH 3
Ph

43.

H 3C OH
Ph
OH



 
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.
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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

O H+
H2O O

HO

O

O

OH

O

1. NaOEt

O
OEt

OEt 2. BrCH
3

OH
NMe2

+ HNMe 2
H

OH

O
A

CH 3

O

H+
H2O

NMe 2

O
Ph

B

5
 

OH

NMe 2
H

NaOMe
OCH3 MeOH

C

O

O

Ph

OCH3
Ph

O
Ph
A

OH

OCH3 Ph

H 3CO O O
Ph
OCH3
OCH3
B
C
Ph



 
F. Elements of Unsaturation/Hydrogenation Problems. For each problem there will be multiple
satisfactory solutions.
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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. O3

52.

O
H

2. Me 2S

O

O

H

1. O3
2. Me 2S
H

53.

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Any
of
three
answers

O

1. O3
2. Me 2S

54.

O
H

H
O

H

H

1. O3

55.

2. Me 2S

O

+

O

O

O

+
H

H

O

+
H

O

6
 



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