CHEM 234, Spring 2010
FINAL EXAM
ANSWER
PRINTED
FIRST NAME
Ian R. Gould
KEY
PRINTED
LAST NAME
ASU ID or
Posting ID
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Total (incl Extra)________/375+5
Extra Credit_____/5
H
He
B
N
O
F
Ne
Na Mg
Al Si P
S
Cl
Ar
H/H
~1.0
Me/Me
~0.9
Ga Ge As Se Br
Kr
H/Me
~1.4
Et/Me
~0.95
In Sn Sb Te I
Xe
Me/Me
~2.6
i-Pr/Me
~1.1
Tl Pb Bi Po At
Rn
Me/Et
~2.9
t-Bu/Me
~2.7
K
Ca
Sc Ti V
Cr Mn Fe Co Ni Cu Zn
Rb Sr
Y
Zr Nb Mo Tc Ru Rh Pd Ag Cd
Cs Ba
Lu Hf Ta W
small range
range of values
broad peak
Re Os Ir Pt Au Hg
O H
C N
N H
C O
C
H
C
C
N
2850–2960
H
1680
C
OR
2000
10
200
R C OH
O
C
H
O
C CH3
–H2C NR2
C CH2
8
160
7
140
6
120
5
100
Aromatic
CR2
C CH
4
80
3
60
RC
CR
Alkyl
3Y > 2Y > 1Y
2
40
–OCH2–
R C N
R2C
H
~15
C C
1500
–OCH2–
NMR Correlation Charts
Aromatic Ar H
mainly 8 - 6.5
9
180
~2
H
NR2
1650
2500
H
H
C
1710
3000
11
220 O
~8
~2
C C
O
2200
–H2C X
(δ, ppm)
H
~10
H
1600
O
C
amine R NH2 variable and condition
alcohol R OH dependent, ca. 2 - 6 δ
O
C H
H
C C
1735
CH
broad ~3000
O
R C OH
~7
C C
H
C
O
C O H
3500
H H
O
H
broad with spikes ~3300
broad ~3300
N
C
2200
O H
1600–1660
O
2720–2820
2 peaks
3000–
3100
N H
C
C
H
C
3300
Approximate Coupling
Constants, J (Hz), for
1
H NMR Spectra
Infrared Correlation Chart
H
Gauche
Eclipsing
usually
strong
O
C H
(cm-1)
C
Interaction Energies, kcal/mol
Li Be
1
20
0
0
Alkyl 3Y > 2Y > 1Y
C X
C NR2
CHM 234, Spring 2010, FINAL EXAM
NAME
- 2-
Question 1 (16 pts.) Provide IUPAC names for the following structures, do not forget to use
E/Z and R/S as appropriate.
O
7
6
5
4
a)
3
2
1
OH
6-bromo-7-phenylhept-(5Z)-enoic acid
Br
6
Br
b)
7
O
4
5
3
OH
2
7-bromo-(5R)-hydroxyheptan-2-one
1
Question 2 (10 pts.) Rank the energies of an electron in each of the following π-molecular
orbitals. Give a BRIEF explanation for your choice.
A
•
D
B
C
D
C < –––
–––
lowest energy
A < –––
< –––
B
highest energy
an electron will be lower in energy the bonding interactions in the molecular orbital, and
higher in energy the more antibonding interactions, orbital D is non-bonding
Question 3 (14 pts.) On each side of the following equilibrium, identify the stronger and
weaker acid and base, identify which acid would have the LOWER pKa, indicate on which
side the equilibrium would lie, and give a brief explanation for your choices.
O
O
O
weaker base
+
O
N
H
weaker acid
larger pKa
O
O
stronger acid
smaller pKa
+
N
H
stronger base
The second pair of nonbonding electrons on the deprotonated amide are stabilized by
conjugation into the C=O bond, lowering their energy and stabilizing the anion. This ion is
thus the weaker base, corresponding to the stronger acid.
the stronger base is stronger because of the presence of the nitrogen that acts as a
strnger donating group to destabilize the enolate anion, compared to the weaker oxygen
donating group in the ester
CHM 234, Spring 2010, FINAL EXAM
NAME
-3 -
Question 4 ( 14 pts.) Which is the stronger acid, A or B? Give a BRIEF explanation, including
the drawings of all relevant structures and ALL resonance contributors as appropriate.
O
O
H
H
A
B
–H+
–H+
O
O
O
O
O
The anionic conjugate base has more resonance structures, is more stable,
thus B is more acidic.
Question 5 (14 pts.) Rank in order of increasing rate of reaction with a Grignard reagent,
give a BRIEF explanation.
O
Ph
C
O
Cl
Ph
A
slowest
C
O
O
Me
Ph
B
B
<
C
C
Me
C
<
A
fastest
The Grignard is a nucleophile/Lewis base, the carbonyls are the electrophiles/Lewis
acids, the electrophilic atom is teh C of the C=O, in A the electrophilic Cl activates this
carbon towards nucleophilic attach and in B the -OMe is resonance electron donating
and deactivates this carbon towards nucleophilic attack
Extra Credit Question (5 pts). Which kind of molecule was used in the new Two-Electron
Sensitization Process for Photography that Dr. Gould worked on when at Kodak?
amine
ester
amide
aldehyde
-4-
CHM 234, Spring 2010, FINAL EXAM
NAME
Question 6 (14 pts.) Rank in order of increasing rate of electrophilic aromatic substitution, e.g. Br2/FeBr3.
O W
N
A
N
N
O
C
B WD
WD
slowest
H
D
H
A
B
<
C
<
O
N SD
H
fastest
In electrophilic aromatic substitution the benzene ring is a Lewis base/nucleophile, donating
substituents activate towards reaction and withdrawing substituents deactivate towards
reaction, thge substituents are as indicated (W = withdrawing, WD = weak donating, D=
strong donating, SD = strong donating, N = neutral, neither withdrawing or donating)
Question 7 (24 pts.) For the following reaction, give a curved arrow-pushing mechanism
• Draw all of the resonance contributors for important intermediates.
• Do NOT use +H+/-H+ notation, show exactly where each proton goes to and comes from
• Indicate the Lewis acid and base at each step as appropriate and if they are also
H
Bronsted acids/bases
LA/BA
O
O H
O
H
H
LB/BB
HCl (cat.)
H2O
H
LB/BB
O
H
O H
LA/BA
O H
H
H
b) Draw a properly labelled reaction energy diagram, indicated the positions of the reactants,
intermediates, transition states and products, but you do not draw the structures of any of
these on the diagram.
‡
‡
Energy
intermediates
reactants
products
Reaction Coordinate
-5-
CHM 234, Spring 2010, FINAL EXAM
NAME
Question 8 (72 pts)
Provide the missing products, reagents/conditions or reactants, as required. Do not
forget to include absolute and relative stereochemistry as appropriate.
NH2
1. excess CH3I
a)
2. Ag2O/ H2O
3. heat
1.
O
b)
O
MgBr
2. H3O+
O
OH
O
O
N
HNMe2 / H+ (cat.)
c)
H2/Pd/C
CO,HCl
d)
H
AlCl3 / CuCl
O
H
H
O
NH2
O
OH
1. HONO
e)
2. H3O+
OCH3
OCH3
CN
f)
heat
+
CH3
(±)
CN
CH3
-6-
CHM 234, Spring 2010 FINAL EXAM
NAME
Question 8, Contd...
Provide the missing products, reagents/conditions or reactants, as required. Do not
forget to include stereochemistry as appropriate.
O
O
TsOH (cat.)
g)
heat
Br
NH2
1.
h)
Na+ –N3
2. LiAlH4
3. H3O+
O
HN
NH2
O
i)
O
+
O
CO2H
Question 9 (18 pts)
a) Give the reactants AND reagents/conditions that would allow you to synthesize the
provided structure in a Claisen reaction
O
O
+
EtO
OEt
excess
O
1. Na+ -OEt
OEt
2. H3O+
O
EtO
OEt
Ph
Ph
b) Give the reactants AND reagents/conditions that would allow you to synthesize the
following structure in an Aldol condensation.
O
H
any reasonable
acid/base
heat
O
O
-7-
CHEMISTRY 234, Spring 2009 FINAL EXAM
NAME
Question 10 (16 pts) For the following cycloaddition reaction:
a) Give the curved arrow-pushing describing product formation
Δ
+
Et
Et
b) On TOP OF THE structures below, draw the HOMO for reactant A and the LUMO for reactant B
Et
B
A
c) USING F.M.O. theory, explain whether the provided product is allowed or forbidden,
include the terms suprafacial and/or antarafacial in your explanation
the reaction is suprafacial on both reactants, the product is thius allowed since
suprafacial/suprafacial results in both bonding interactions in the transition state according to the
HOMO/LUMO overlap
Question 11 (20 pts) Give the mechanism for the following reaction
• AS APROPRIATE, SHOW WHERE ALL PROTONS COMES FROM AND GO TO (no +H+/-H+)
• DRAW ALL RESONANCE CONTRIBUTORS for the intermediates as approriate
• At each INTERMOLECULAR step, INDICATE THE Lewis acid and base (LA or LB) and
whether they are also Bronsted acids and bases (BA or BB) as appropriate
H
..
..
..
..
O
OH OH
..
H
..
H
O+
H3O+
H
+
HOH OH
: OH
+
OH
O
H
:O
H
CHEMISTRY 234, Spring 2010 FINAL EXAM
-8-
NAME
Question 12 (20 pts.) Give a curved arrow-pushing mechanism for the following reaction
• You can give an "abbreviated mechanism, i.e. you may use +H+ and -H+
• IT IS NOT NECESSARY TO INDICATE THE LEWIS/BRONSTED ACID/BASE AT EACH STEP
• BUT, draw all resonance structures for the intermediates
• Add non-bonding electrons and C–H bonds as necessary
O
O
1.
O
O
Na+ –OEt/EtOH
OEt
2. H3O+
OH
OEt
O
+H+
O
O
O
OEt
O
OH
OEt
+H+
O
O
O
OEt
O
OEt
O
O
–H+
O
-9-
CHM 234, Spring 2010, Final Exam
NAME
Question 13 (25pts) Provided are spectra for a compound with molecular formula C6H12O2
degrees of unsaturation
a) Give the degrees of unsaturation 0________________
b) On the infrared spectrum, indicate the peaks that identify the functional groups in the
molecule (including C(sp3)-H). Indicate BOTH the functional group, and where
appropriate, the specific BOND in the functional group that corresponds to the peak.
3188
1436
2903
2969
H
1356
958 877
sp3
2981
O
O
1189
1731
c) draw the structure and clearly indicate which hydrogens correspond to which
signals in the proton nmr spectrum (only)
3H d
singlet
O
H3C
d
6H a
doublet
a
CH3
CH2
O c CH b
CH3
a
2H c
doublet
b
1H
nonet
CHM 234, Spring 2010 FINAL EXAM
- 10 -
NAME
Question 14 (20 pts.) Show how you would make the target componds on the right from the
starting compounds on the left. Show reagents and conditions where appropriate, and the
structures of important intermediate compounds. Do not show any (arrow pushing)
mechanisms. If necessary, you must indicate steps that require separation of isomers
NO2
O
AlCl3
Cl
Cl
HNO3/H2SO4
O
O
Cl2/AlCl3
Zn/Hg/HCl/H2O
Cl
Cl
Question 15 (40 pts) Show how you would make the target componds on the right from the
starting compounds on the left. Show reagents and conditions where appropriate, and the
structures of important intermediate compounds. Do not show any (arrow pushing) mechanisms.
These 2 questions use only reactions from the basic sets that were provided on the class website
a)
OH
1. BH3.THF
2. -OH / H2O2
OH
O
PCC
1. CH3MgBr
2. H3O+
CO2H
b)
OH
Br2 / FeBr3
Br
1. Mg.THF
2.
O
Na2Cr2O7/H2SO4/H2O
CHM 234, Spring 2010 FINAL EXAM
NAME
- 11 -
Question 16 (40 pts.) In each case, synthesize the (target) molecules on the right from the
starting molecules the left. this can not be done in one reaction. Give reagents and
conditions and the intermediate molecules at each step. Do not show any mechanisms or
transient intermediates.
HO
HO
a)
HO
HO
NH2
dopamine
Br2 / hν
1. LiAlH4
HO
2. H3O+
HO
Na+ –CN
HO
HO
Br
CN
b)
PH
HBr
N
H
Br
PH
SOCl2
CO
N
H
Mg.THF
SOCl2
1. CO2
MgBr
2. H3O+
CO2H
COCl