HERE - Organic Chemistry at Arizona State University

CHEM 234, Spring 2015
PRINTED
FIRST NAME
ANSWER
Final Exam
PRINTED
LAST NAME
KEY
Ian R. Gould
ASU ID or
Posting ID
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• MOLECULAR MODELS ARE ALLOWED
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• DO NOT USE RED INK
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• DON'T CHEAT, USE COMMON SENSE!
5__________/20
H
6__________/64
Li Be
B
N
O
F
Ne
a)_______/8
Na Mg
Al Si P
S
Cl
Ar
b)_______/8
K
Ga Ge As Se Br
Kr
c)_______/8
Rb Sr
Y
In Sn Sb Te I
Xe
d)_______/8
Cs Ba
Lu Hf Ta W
Tl Pb Bi Po At
Rn
He
Ca
Sc Ti V
Cr Mn Fe Co Ni Cu Zn
Zr Nb Mo Tc Ru Rh Pd Ag Cd
Re Os Ir Pt Au Hg
C
e)_______/8
f)_______/8
g)_______/8
h)_______/8
7__________/8
8__________/12
9__________/28
10__________/10
11__________/18
12__________/20
13__________/36
a)________/20
b)________/16
14__________/40
a)________/20
b)________/15
c)________/15
15__________/40
a)________/20
b)________/20
Extra Credit_____/5
Total (incl Extra)________/375+5
CHM 234, Spring 2015, FINAL EXAM
NAME
- 2-
Question 1 (12 pts.) Provide IUPAC names for the following structure, do not forget to use E/Z
and R/S as appropriate.
a)
(2S),4-dimethyloct-(4E)-enoic acid
CO2H
Question 2 (20 pts.) For each of the structures A, B and C:
a) Add the hydrogen atom to the line-angle structure that would be the most Bronsted acidic
b) Rank A, B and C in order of increasing Bronsted acidity and give a brief explanation
c) for structure A ONLY, draw the conjugate base, including all resonance contributors
O
O
H
O
-H+
O
O
O
A
O
O
H
H
A
weakest
acid
O
B
<
C
<
B
strongest
acid
C
Bronsted acidity is determined by the stability of the conjugate base anion, the less stabvle teh
conjugate base the weaker the acid
in each case the conjugate bases are delocalized enolate anions
in A the enolate is destabilzied by the electron donating oxygen atom of the ester, the base
anion from A is thus the least stable, A is thus the weakest acid
in B the oxygen is not electron donating, but it weakly stabilizes the conjugate base anion via
the inductive effect, B is thus the strongest acid
CHM 234, Spring 2015, FINAL EXAM
-3 -
NAME
Question 3 (25 pts.) For the following acid/base equilibrium:
a) draw the curved arrows showing bond making/breaking
b) indicate which is the STRONGER and the WEAKER acid and base on each side
c) Indicate which acid has the larger and which the smaller pKa
d) give a BRIEF explanation for your choice of stronger/weaker that includes the phrase "energy
of the electrons"
H
H
H
H
H
H
slower
N H
N
N
N
H
H + H
+
faster
weaker base
weaker acid
stronger acid
stronger base
larger pKa
smaller pKa
equilibrium lies on THIS side
the weaker base has the lower energy electrons, the non-bonding electrons
in A are stabilized by resonance, are this lower in energy
e) Indicate which reaction (left to right or right to left) is faster and which is slower and indicate
on which side the equilibrium lies
f) Draw a PROPERLY labelled reaction energy diagram, indicate the position of the transition
state and include a drawing of the transition state
Energy
H
‡
H
H
‡
N
N
H
H
Reaction Coordinate
Question 4 (12 pts) Explain why sodium borohydride (NaBH4) will reduce a ketone but will not
reduce an ester.
O
O
O
O
O
NaBH4/EtOH
OH
O
NaBH4/EtOH
no reaction
the BH4– anion is a Lewis base, the carbonyl carbon is Lewis acidic
in the ester the oxygen atom acts as an electron donating group which decerases the Lewis
acitity of the carbonyl carbon
OR....
the minor resonance contributors show that the partial positive charge is delocalized onto
the oxygen in the ester, which decreases its electrophilicity
-4-
CHM 234, Spring 2015, FINAL EXAM
NAME
Question 5 (20 pts) Give a curved arrow pushing mechanism for the following reaction
• For 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
• You MUST show where every proton comes from and goes to, no abbreviated +H+/-H+ notation
you do NOT need to show resonance contributor for the intermediates in this case!
H
H
O
O
H3O+
OCH3
HO
H
H
O
H
H
O
H
O
OCH3
O
O
O
OCH3
OCH3
H
O H
H
H
O
O
O H
O
H
O
OCH3
OCH3
O
H
H
H
H
H
OCH3
O
H
O
H
H
H
O
H
H
H
O
+ CH3OH
H
OR.... the order of the steps can be different, for example, in the first step you can protonate
the -OCH3 and have it leave first and so on...
Extra Credit Question (5 pts). Which functional group formed the basis of the new "twoelectron sensitizer" molecule that enhances the speed of motion picture film?
amine
ester
amide
aldehyde
-5-
CHM 234, Spring 2015, FINAL EXAM
NAME
Question 6 (64 pts) Provide the missing major organic products for the following reactions. Do
not forget to include stereochemistry as appropriate and INDICATE ANY RACEMIC
MIXTURES.
O
a)
H2N
OH
Ph
Cl
NH
Ph
OH
O
1 equivalent
NMe2
NMe2
b)
CO2CH3
heat
+
(±)
CO2CH3
1 equivalent
c)
O
O
HO
O
O
O
O
O
H+ cat.
O
H
O
d)
HCl cat.
heat
H
OH
Br
1. NaCN
e)
H
or other isomer
H
H2N CH2 H
2. LiAlH4
3. H3O+
OH
O
1.
f)
MgBr
(±)
2. H3
O+
-6-
CHM 234, Spring 2015 FINAL EXAM
NAME
Question 6, Contd... Provide the missing major organic products for the following
reactions. Do not forget to include stereochemistry as appropriate and INDICATE
ANY RACEMIC MIXTURES.
O
O
+
g)
EtO
OEt
excess
O
1. Na+ -OEt
OEt
EtO
2. H3O+
1.
O
h)
MgBr
2. H3O+
O
OEt
Ph
Ph
O
O
OH
O
Question 7 (8 pts) Give the reactants AND reagents/conditions that would allow you to
synthesize the following structure in an Aldol condensation.
O
any
reasonable
acid/base
O
H
heat
O
Question 8 (12 pts) Give the product of complete hydrolysis of the following structure
(hydrolyze all functional groups that can be hydrolyzed)
N
C
H3O+
CO2H
heat
O
O
O
CHEMISTRY 234, Spring 2015 FINAL EXAM
-7-
NAME
Question 9 (28 pts) The purpose of this question is to determine whether the provided product is
allowed or forbidden using FMO theory
a) First, give the curved arrow-pushing describing product formation
Et
Et
Δ
Me
Me
+
Pr
Pr
Me
A
B
Et
Me
Et
b) Now, state whether the reaction to give the PROVIDED product (which may or may not be
allowed) is suprafacial or antarafacial with respect to both reactants A and B
antarafacial
reaction to give the PROVIDED product was (supra or antara) __________________
for reactant A
suprafacial
reaction to give the PROVIDED product was (supra or antara) __________________ for reactant B
c) On TOP OF THE structures below, draw the HOMO for reactant A and the LUMO for reactant B
Et
HOMO
A
Me
Pr
Me
Et
LUMO
B
d) USING F.M.O. theory, state whether the ALLOWED product of this reaction (which may or
may not be the one that is provided) should be formed in a suprafacial/suprafacial or
suprafacial/antarafacial reaction.
suprafacial/suprafacial
forbidden
e) Is the PROVIDED product allowed or forbidden? _______________
Question 10 (10 pts.) Indicate which of the following two structures A and B you would expect
to be the stronger Bronsted BASE, and give a brief explanation that includes the term
"energy of the eletrons". Assume that both structures are completely FLAT.
A
B
In A the electrons are in an aromatic system and are thus stabilized and lower in energy,
less reactive, and thus a weaker base, in B the electrons are in an antiaromatic system
CHEMISTRY 234, Spring 2015 FINAL EXAM
NAME
-8-
Question 11 (18 pts.) Give a curved arrow-pushing mechanism for the following reaction that
shows formation of BOTH products. There are no other reagents or catalysts in this reaction
and the solvent is not involved. SHOW WHERE EVERY PROTON COMES FROM AND GOES
TO (no +H+/-H+). Indicate the Lewis acid and base (LA or LB) at each INTERMOLECULAR
step and whether they are also Brønsted acids and bases (LA/BA or BA/BB)
O
O
O
H
NH2
N
O
+
+
HO
O
HO
LB
LA
HO
acetominophen - painkiller
O
O
O
O
N
H
O
N
H
H
HO
HO
LB/BB
H
O
LA/BA
Question 12 (20 pts.) Give a curved arrow-pushing mechanism for the following reaction. You
can use the abbreviated +H+/-H+ notation, but include all important resonance contributors for
O
the intermediates.
O
H+ cat.
heat
+H+
H
O
–H+
O
O
H
H
O
O
H
H
O H
H
H
O ••
OH2
O
O
O
+H+
+H+
–H+
–H+
O
O
OH
-9-
CHM 234, Spring 2015, Final Exam
NAME
Question 13 (36 pts.) Give a curved arrow-pushing mechanism for the following two reactions
• SHOW WHERE EVERY PROTON COMES FROM AND GOES TO
• Indicate the Lewis acid and base (LA or LB) at each INTERMOLECULAR step and
whether they are also Brønsted acids and bases (LA/BA or BA/BB)
H
LA/BA
O
O
O
LB/BB
H3O+
H
H
+ HOEt
a)
OEt
OH
heat
O
LA
O
H
O
OEt
H
H
H
H
O
LB/BB
O
H
OH
OH
LA/BA
OEt
H
OH
H
O
O
H
O
OH
H
LB/BB OH
LB
OEt
OEt
O
LA/BA H
HO
b)
LA/BA
OH
H
OH
O
H
H
LB/BB
O H LB/BB
H2O/NaOH
HO
O
H
O H
H
O
LA/BA
Et
CHM 234, Spring 2015 FINAL EXAM
NAME
- 10 -
Question 14 (50 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. For question a) you must indicate steps that require separation of isomers.
SO3H
a)
CH3
separate isomers
CO/HCl
AlCl3
NO2
CHO
SO3/H2SO4
CHO
CH3
Zn/Hg/HCl/H2O
NO2
NO2
THE NEXT TWO SYNTHESIS PROBLEMS, b) and c), USE ONLY REACTIONS FROM THE
"MINIMAL SET OF REACTIONS" PROVIDED RECENTLY ON THE CLASS WEB PAGE!
ignore
stereochemistry
b)
PCC
NBS, hν
Na+ –OH
Br
O
1. BH3.THF
2. –OH/H2O2
OH
c)
OH
Br
K+ –O-t-Bu
O
MCPBA
Na
CHM 234, Spring 2015 FINAL EXAM
- 11 -
NAME
Question 15 (40 pts.) Synthesize the (target) molecule on the right from the starting
molecule 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.
N
a)
1. LiAlH4
2. H3O+
1. HNMe2/H+
2. H2/Pd/C
HBr, ROOR
O
Br
MgBr 1.
Mg.THF
H
O
OH
O
PCC
2. H3O+
N
CO2H
COCl
O
b)
O
NBS/hν
EtOH
COCl
Br
SOCl2
Mg.THF
Br
MgBr
1. CO2
2. H3O+
CO2H
`