8/16/2019 mit-o2-h3

1/10

Massachusetts Institute of Technology 5.13, Fall 2006

Dr. Kimberly L. Berkowski Organic chemistry II

EXAM 3 EXTRA PROBLEMS

What to expect on Exam #3:

1. 

~1 Labeling experiment2.

 

~2 Mechanisms

3. 

~2 Syntheses

4.  ~5 Transformations – supply missing product

5. 

~5 Transformations – supply missing reagents

6. 

~3 General question

8/16/2019 mit-o2-h3

2/10

1. 

(4 points each, 8 points total) In the boxes, please provide the reagents for the

illustrated transformations. More than one step may be required.

2.  (2 points each, 8 points total) Please provide the products of the following reactions. If

no reaction is expected, write “NR”.

 Name_____________________1

O

OHi-Pr 

O

Hi-Pr 

O

OHi-Pr 

i-Pr Br  

(a)

(b)

Figure by MIT OCW.

Et Cl

O

Et OH

O

Et OMe

O

(a)

(b)

(c)

(d)

Et  NMe2

O

1. Excess Na BH4

2. Workup

2. Workup

1. Excess MeMgBr 

2. Workup

1. Excess MeLi

2. Workup

1. Excess LiAlH4

Figure by MIT OCW.

8/16/2019 mit-o2-h3

3/10

3.  (2 points each, 16 points total) Please provide the requested products or reagents. If no

reaction is expected, write “NR”.

 Name___________________

2

 NH2   N2   Br 

(d)

(c)

 NH2

O

O

n-BuH2O

H3O+

Me Me

H2 N

cat. H+

(b)1. LiAlH4

2. workup

Me

MeMe

Me   NH2 NH2

H2O2, ∆

(a)

O

n-Bu

CN

OH

Figure by MIT OCW.

8/16/2019 mit-o2-h3

4/10

 4. (11 points) Provide a detailed mechanism for the illustrated conversion of acetic acid

(A) to acetyl chloride (B).

OHMe

O

 ClMe

OO

+S

Cl   Cl

+   +SO2   HCl

BA

 Name___________________

3

Figure by MIT OCW.

8/16/2019 mit-o2-h3

5/10

5. (11 points each, 22 points total) Please provide syntheses for only two of the three

indicated compounds. All the carbon atoms should be derived from the allowed starting

materials. You may use any common reagents.

 Name___________________

4

Allowed Starting Materials:

Me

MeMe Me

Me

Me CO2OH OH

Me

Me

C N

Me

Me

HO

MeMe NHPick Two:

Synthesis # 1:

Figure by MIT OCW.

8/16/2019 mit-o2-h3

6/10

5. (Continued)

 Name_______________________

5

Allowed Starting Materials:

 Me

 Me

 Me

 Me Me

 Me

 Me Me

CO2 OH

 Me

Me-OH

Me

Me

C N

HO

 NH

Pick Two:

Synthesis #2:

Figure by MIT OCW.

8/16/2019 mit-o2-h3

7/10

6.  (11 points) Provide a synthesis that will selectively convert A to B. Show all the key

intermediates and furnish all the important reagents. This is not a one-step process.

Me

O

Me

O

A

HO

B

 

 Name_____________________

6

Figure by MIT OCW.

8/16/2019 mit-o2-h3

8/10

7.  Methyl acetimidate (A) is hydrolyzed in aqueous sodium hydroxide to give mainly

acetamide and methanol (eq 1). In aqueous acid, A hydrolyzes to give primarily

methyl acetate and ammonium ion (eq 2).

a) Provide a detailed mechanism for the illustrated process. Please show all arrow

 pushing.

 b) Provide a detailed mechanism for the illustrated process. Please show all arrow

 pushing.

c) Briefly explain why the two reactions provide different products.

7

OMe  NH2MeA

H2O

 NH

Me

O+ (1)  MeOH

HO-

Figure by MIT OCW.

OMe   OMeMeA

H2O

 NH

Me

O

 NH4+   (2)excess H

+

Figure by MIT OCW.

8/16/2019 mit-o2-h3

9/10

8.  Synthesize the indicated compounds from the allowed starting materials shown

 below. All of the carbons of the target compounds should be derived from the

allowed starting materials.

9. 

Provide the best stepwise mechanism for the illustrated process. Please show all

arrow pushing.

10.  (a) Provide the best mechanism. Please show all arrow pushing.

(b) Provide the best mechanism. Please show all arrow pushing.

MeOH

MeMeMe

Me

Me

MeMe

Me

Me   OH   CO2   ethylene   CNO

O

O

O

H

H

H

H

 N

 N

 N

Br 

Br Br 

 NH2

 Allowed starting materials

(b)

(c)   (d)

(e)

Figure by MIT OCW.

+

 NH2

H

 NaBH3CN

 N

OO

H   H

Figure by MIT O

+

Me

H

 N=C-Me  N

Figure by MIT O

+

 NH2 N

  Me

OH

H

H2O

Figure by MIT OC

8/16/2019 mit-o2-h3

10/10

 

11.  Consider the labeling experiments outlined below:

Stop each reaction at 50% convers

and examine the recovered startin

material for incorporation of Ø

Under acidic hydrolysis conditions, would you expect more Ø incorporation into the

amide (eq 1) or the ester (eq 2)? Your answer should include the mechanism for

these reactions.

9

HO

Me  NHMe

+, H2φ

HO

Me OMe

+, H2φ

(1)

(2)

Figure by MIT OCW.