Massachusetts Institute of Technology
5.13: O rganic Chemist ry II
Dr. Sarah A. Tabacco
Hour Exam # 3
N ovember 12, 2003
Printed N ame ________________________
Signature ___________________________
MIT ID # ___________________________
Recitation TA ________________________
General Instructions:
• This is a closed book exam. No books, notes, or calculators allow ed . You
are allow ed to use m olecular m od els.
• Make sure that your exam has 11 pages (includ ing cover, a blank page for
extra w ork, and a period ic table).
• Write your nam e on each page.
• Write answ ers in the spaces provid ed . If you run out of room , use the blank
page and indicate this for your grader.
• Show all of your w ork if you w ish to receive partial cred it.
• Read the instructions carefully, and bud get your tim e.
• GOOD LUCK!!
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6__________/ 11
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8__________/ 11
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Total___________
(out of 100 points)
1. (4 p oints each, 8 p oints total) In the boxes, please p rovid e the reagents for the illu strated
transform ations. More than one step may be requ ired .
a)
O
i-P r
i-P r
Br
OH
b)
O
i-P r
O
i-P r
OH
H
2. (2 p oints each, 8 p oints total) Please p rovid e the prod u cts of the follow ing reactions.
If no reaction is expected , w rite "N R".
a)
O
Et
b)
1. e xce s s Na BH4
Cl
O
Et
c)
1. e xce s s Me MgBr
OH
O
d)
O
Et
2. workup
1. e xce s s Me Li
OMe
Et
2. workup
2. workup
1. e xce s s LiAlH4
NMe 2
2. workup
Name_______________
2
3. (2 points each, 16 p oints total) Please p rovid e the requ ested prod ucts or reagents. If no
reaction is expected, w rite "N R".
a)
O
Me
Me
NH2
NH2
H2 O 2 , ∆
Me
Me
b)
O
Me
H2 N OH
1. LiAlH4
ca t. H+
2. workup
Me
c)
H3 O +
O
n-Bu
NH2
n-Bu
CN
H2 O
d)
NH2
N2
Name_______________
Br
3
4. (12 p oints) The hyd rolysis of a nitrile (A) to a carboxylic acid (C) involves initial
form ation of a p rim ary am id e (B). Provid e a d etailed mechanism for each the follow ing
transform ations.
a)
Me
C
Me
N
Me
H+, H2 O
Me
NH2
A
b)
Me
B
O
Me
O
Me
H+, H2 O
NH2
O
Me
B
OH
C
Name_______________
4
5. (12 p oints) Consid er the labeling experiment outlined below :
O
Me
H2 ∅
Cl
∅H
stop the reaction at 50% conversion
and exam ine the recovered acyl chlorid e
for incorporation of ∅
∅ = isotopically labeled oxygen (18O)
a) Please provide the m echanism for the hyd rolysis reaction show n above, includ ing the
pathw ay for incorporation of ∅ into the acyl chlorid e.
b) What level of ∅ incorporation ("high" or "low ") you w ou ld expect to observe in the
recovered acyl chlorid e? Explain briefly.
c) Based on your answ er to part b, do you think the results of this labeling stud y
d efinitively prove the m echanism of this reaction? Explain briefly.
Name_______________
5
6. (11 p oints) Provid e a d etailed m echanism for the illu strated conversion of acetic acid
(A) to acetyl chlorid e (B).
O
Me
O
OH
A
Cl
S
O
Cl
Me
Cl
S O2
HCl
B
Name_______________
6
7. (11 p oints each, 22 p oints total) Please provid e syntheses for only tw o of the three
ind icated com p ou nd s. All of the carbon atom s shou ld be d erived from the allow ed starting
m aterials. You m ay u se any com mon reagents.
Allow ed Starting Materials:
Me
Me
Me
CO 2
OH
Me
Me OH
Me
Pick Tw o:
Me
C
N
HO Me
Me
Me
Me
H
N
Me
Synthesis # 1:
Name_______________
7
7. (continued )
Allow ed Starting Materials:
Me
Me
Me
CO 2
OH
Me
Me OH
Me
Pick Tw o:
Me
C
Me
N
HO Me
Me
Me
H
N
Me
Synthesis #2:
Name_______________
8
8. (11 points) Provid e a synthesis that w ill selectively convert A to B. Show all of the key
intermed iates and furnish all of the im portant reagents. This is not a one-step process.
O
O
Me
HO
Me
B
A
Name_______________
9