Final Exam
May NAME
KEY
Please read through each problem carefully. Enter your answers in the spaces provided.
Problem 1 12 pts
Problem 2
8 pts
Problem 3
8 pts
Problem 4 24 pts
Problem 5 12 pts
Problem 6 21 pts
RELAX! Think about what you
know.
Try to answer the questions you know and can
do quickly first. Then go back and tackle the
problems you find more challenging.
In the multiple step reaction sequences, look at
what kind of reaction takes place in the second
step to give you clues on what functional group
you need to have after the first step.
Problem 7 12 pts
Problem 8 34 pts
In synthesis problems, try to work the synthesis
forwards AND backwards.
Problem 9 24 pts
Problem 10 20 pts
Problem 11 25 pts
TOTAL
Chem Spring Final Exam
page of 1. The following molecules all have some relatively acid proton. Match the pKa’s that are listed below
with the appropriate molecule by writing the pKa in the boxes. (12 pts)
pKa 0.2, 4, 9, 16, 20, 40
O
O
F3C
OH
NH
OH
O
H
40
H
16
O
H
Ph
O
0.2
H
OH
O
9
20
4
2. In the following Diels Alder reaction, there are two products possible. Circle the major product and
briefly explain why it is formed in a larger amount. (8 pts)
+
+
O
secondary orbital
interaction with the
carbonyl pi-bond
lowers the energy for
this transition state
O
O
O
endo product
O
O
3. Explain why base catalyzed hydrolysis of esters (saponification) is better than acid catalyzed
hydrolysis. (8 pts)
Base Catalyzed Hydrolysis (Saponification)
O
OH
OCH3
O
OH
OCH3
O
O
+
OH
OCH3
Rapid acidbase reaction
takes place
Chem Spring Final Exam
+
O
HOCH3
Carboxylate is a thermodynamic
sink and makes the reaction
essentiall non-reversible. To get
the carboxylic acid, add acid to
protonate.
page of 4. Write the complete mechanism for the acid catalyzed hydrolysis of N-methylbenzamide showing
all intermediates (with appropriate resonance structures) and reaction arrows. (24 pts)
HA (cat)
H2O
O
N
H
CH3
O
Ph
H
HA
NHCH3
O
OH
H
O
Ph
NHCH3
H2O
O
Ph
NHCH3
H
O H
NHCH3
H O
Ph
A
H O
Ph
O H
NHCH3
HA
O
Ph
A
OH
H
Ph
H
O
OH
Ph
H O
O
OH
Ph
O H
NHCH3
H
5. For each pair of molecules below, describe how the Mass Spectrum could be used to tell them
apart. (12 pts)
a)
b)
and
m/z = 91
Chem Spring m/z 105
and
base peak
very little else
Final Exam
about equal likelihood
for C-C breaking
page of 6. Provide the major product or reagent for the reactions below. For ortho-para directors you need
only show the para product. (21 pts)
OCH3
OH
HI
O
Cl
AlCl3
OCH3
OCH3
KMnO4
CO2H
H3C
O
NaBH4
then
H3O+
OCH3
CH3NH2
HA (cat)
N
HNO3
H2SO4
OCH3
OCH3
H2
Pd/C
O2N
OCH3
H2N
HO
O
7. Indicate which of the following molecules are aromatic by circling them. (12 pts)
O
Chem Spring O
N
Final Exam
O
HO
OH
page of 8. Provide the missing major products or reagents for the following. (34 pts)
PhMgBr
then H3O+
O
Ph
OH
MCPBA
or
Br2/H2O
then NaH
PCC
or
CrO3, H3O+
OH
O
Ph3P CH2
CH2
1) Hg(OAc)2
CH3OH
2) NaBH4
H3C
OCH3
1) Br2, HA
2) Pyridine
HO
O
O
OH
HA (cat)
NaBH4
then H3O+
O
CH3NH2
OH
POBr3
pyridine
1) NaH
2) PhCH2Br
O
O CH2Ph
N
H
Chem Spring CH3
Final Exam
page of 9. Provide the missing major products or reagents for the following. (24 pts)
O
Ph
(CH3)2CuLi
SOCl2
OH
Ph
Ph
Cl
LiAlH4 or
BH3
then H3O+
CH3
NH3
O
Ph
O
O
OH
Ph
SOCl2
NH2
Ph
CN
PBr3
O
O
H3CO
Ph
Br
Chem Spring OCH3
NaOCH3
Ph
CO2CH3
CO2CH3
Final Exam
H3O+
heat
O
Ph
OH
page of 10. Show how you would synthesize the following starting from toluene and the ketoester shown
below. Hint: This can be done in 5 steps. (20 pts)
CH3
O
and
O
O
EtO
O2N
CH3
HNO3
H2SO4
CH3Cl
AlCl3
CH3
O2N
CH3
O2N
CH3
NBS
peroxides
O
Br
CH2
EtO
O
O2N
O
CO2Et
NaOEt
O2N
CH2
Br
H3O+
heat
O
O2N
Chem Spring Final Exam
page of 11. Answer the following questions about an unknown molecule with a molecular formula of C5H10O.
The IR and 1H NMR are shown below. The 13C NMR shows resonances at 210, 45, 22, and 16
ppm. (25 points)
How many degrees of unsaturation does the molecule possess?
What type of functional group does the carbon
resonance at 210 ppm represent?
What
is
the
structure of the
unknown molecule?
Chem Spring 1
KETONE
O
Final Exam
page of Infrared Stretching Absorptions
Functional
Group
Wavenumber
Range (cm-1)
Absorption
Strength
medium-strong
2850-2960
C H
3020-3100
C H
C H
3300
below 3000
medium
above 3000
strong
above 3000
broad-strong
O H
3400-3650
N H
3300-3500
medium
C C
C N
O C O
2100-2260
medium
C O
1680-1750
strong
C C
1640-1750
medium
C C
800-1300
medium
C O
1050-1150
medium
#H's = #peaks
strong
<1000
C X
notes
Alkene out of plane bending
H
H
H
910 and 990 strong
C C
H
C C
R
H
R
R
R
H
R
H
890
C C
R
H
H
R
C C
R
strong
C C
R
970
700
strong
815
strong
R
strong
H
Chem Spring Final Exam
page of Typical NMR Chemical Shifts
Functional
Group
Type
C H
Alkane
0.7 -1.8
10 - 60
C C H
Allylic or next
to carbonyl
1.6 - 2.4
30 - 60
X C H
next to
halogen or
alcohol
2.5 - 4.0
20 - 85
next to oxygen
of an ester
4.0 - 5.0
50 - 85
vinylic
4.5 - 6.5
110 - 150
aromatic
6.5 - 8.0
110 - 140
aldehyde
9.7 - 10.0
190 - 220
alcohol
varies widely
will exchange with D2O
carbonyl of
ester, amide, or
carboxylic acid
(X = O, N)
N/A
165 - 185
carbonyl of
ketone or
aldehyde
N/A
190 - 220
O
C O C H
C H
C
H Chemical
Shift (ppm)
1
C Chemical
Shift (ppm)
13
H
O
C H
O H
O
C X
O
C
Chem Spring Final Exam
N/A
page of