UNIVERSITY OF WINDSOR
Chemistry and Biochemistry
Chemistry 59-235
Final Exam
Apr. 17, 2012
Time: 3 hours
Answer all questions in the exam booklet(s). Use the following values for molecular weights: C,
12.011; H, 1.008; Br, 79.904; Cl, 35.453; O, 15.999; N, 14.007
1.
Predict the predominant product of the following substitution reaction on the indicated
substituted nitrobenzene. Explain the expected regiochemistry in terms of the
reasonable possible resonance forms of the temporarily de-aromatized intermediates,
including the complete set and all steps for the actual reaction pathway. Reaction at
sites not bearing a halogen may be ignored. (10 marks)
F
O
CH 3O -
OCH3
??
2.
The following two reactions may or may not give different products, and one of them
proceeds more slowly than the other. Indicate which product(s) are obtained, which
reaction is faster (or slower), and for both clearly explain the reasons why. Note: In
terms of size, isopropyl > bromide. (10 marks).
Br
Br
KOt-Bu
KOt-Bu
t-BuOH
3.
t-BuOH
Predict the major products of the following transformations. Mechanisms are not
necessary, but showing your work may be useful (5 marks each, 50 total).
a)
O
OH
HO -(aq)
HO
b)
Cl
OCH3
Na + -NH 2
Cl
1)
2) LiAlH 4
c)
O
Cl2 (1 equiv)
FeCl3
H2 , Pdo
Br2
h
d)
H2 , Pd
H2 SO4
e)
KMnO4
H+
4.
SO 3
H 2SO4
show valence bond
structure of J for
full marks
Show by equation (normally several steps) how you could prepare the products
illustrated below from the given starting materials. You may use any other reagents you
deem fit. Show all reagents, conditions, and isolable intermediates. Mechanisms are not
necessary, but showing your work may be a help. Do any four (40 marks).
a)
H3 C
NH
N
H
O
b)
CH 2
O
c)
OH
OCH 3
OH
d)
e)
NH 2
5.
Cl
F
Rank all four of the following reactions in their relative ability to undergo E2 elimination
as opposed to an E1. Include the reasons for your ordering and the product structures. It
is possible that there might be small amounts of substitution products in some cases;
you may ignore the substitution products. Note: iPr2NEt is just like Et3N, except it is
more sterically hindered and gives less SN2 side products. Dielectric const., THF = 7.6,
H2O = 78.3 (15 marks).
Br
Br
i-Pr 2NEt
THF (solvent)
i-Pr 2NEt
THF (solvent)
Cl
OH
H2 SO4(aq)
6.
K+ -Ot-Bu
THF (solvent)
Rank the following in terms of their preference for an E2 elimination as opposed to an
SN2 substitution. I am not asking for products or rationale. (5 marks)
Br
Br
Br
Br
Br
O
KOt -Bu
t-BuOH
NaOEt
EtOH
7.
NaOEt
EtOH
Na+ -O
EtOH
KOt -Bu
t-BuOH
The following compound has been analyzed, revealing a composition C, 54.53%; H,
9.15%; O, 36.32%. The mass spectrum gives a highest m/e of 132. The IR (infrared) and
1
H NMR spectra are also included below. Which of the following structures is the most
reasonable candidate for the compound in question, and why? Assign the NMR
spectrum, showing the comparison of your calculated chemical shifts with the observed
ones. Your answer should include the assignment of the most important features (i.e.,
the starred ones) of the IR spectrum. (15 marks)
OH
O
O
O
O
O
O
O
O
O
Bonus: Furan (and some modified thiophenes and pyrroles), undergoes a very different type of
reaction, that is not a substitution, with alkenes bearing electron withdrawing groups. Can you
propose how the following is occurring?
NO2
O
+
OEt
O
NO2
CH2Cl2
O
CO2Et
H Nuclear Magnetic Resonance Chemical Shifts
Chemical Shifts in ppm downfield from tetramethylsilane (defined as = 0.000 ppm). Values are
approx. 0.2 ppm).
Protons on a Carbon Adjacent to a Functional Group
Functional Group
saturated system
M-C=C
M-CC
M-Phenyl
M-Cl
M-Br
M-I
M-OH
M-OR
M-O-Phenyl
M-OC(=O)R
M-OC(=O)Ph
M-CH=O
(aldehyde)
M-C(R)=O (ketone)
M-COOH
(acid)
M-COOR
(ester)
M-NR2
M-NHC(=O)R
CH3
0.8
1.6
1.7
2.2
3.0
2.7
2.2
3.2
3.2
3.9
3.6
3.8
2.2
2.1
2.1
2.0
2.4
2.9
(0.8)
(0.9)
(1.4)
(2.2)
(1.9)
(1.4)
(2.4)
(2.4)
(3.1)
(2.8)
(3.0)
(1.4)
(1.3)
(1.3)
(1.2)
(1.6)
(2.1)
CH2
1.2
2.0
2.2
2.6
3.4
3.4
3.1
3.4
3.4
4.1
4.1
4.2
2.4
2.3
2.3
2.2
2.6
3.3
(0.8)
(1.0)
(1.4)
(2.2)
(2.2)
(1.9)
(2.2)
(2.2)
(2.9)
(2.9)
(3.0)
(1.2)
(1.1)
(1.1)
(1.0)
(1.4)
(2.1)
CH
1.6
2.4
2.8
2.8
4.0
4.1
4.2
3.8
3.6
4.5
4.5
5.0
2.5
2.6
2.5
2.5
2.9
3.9
(0.8)
(1.2)
(1.2)
(2.4)
(2.5)
(2.6)
(2.2)
(2.0)
(2.9)
(2.9)
(3.4)
(0.9)
(1.0)
(0.9)
(0.9)
(1.3)
(2.3)
Protons on a Carbon Once Removed from a Functional Group
Functional Group
M-C-CH2
M-C-C=C
M-C-CC
M-C-Ph
M-C-Cl
M-C-Br
M-C-I
M-C-OH (or OR)
M-C-OPh
M-C-OC(=O)R
M-C-CH=O
M-C-C(R)=O
M-C-CO2R
M-C-NR2
M-C-NH-C(=O)R
CH3
0.8
1.0
1.2
1.2
1.5
1.8
1.8
1.2
1.3
1.3
1.1
1.1
1.1
1.0
1.1
(0.2)
(0.4)
(0.4)
(0.7)
(1.0)
(1.0)
(0.4)
(0.5)
(0.5)
(0.3)
(0.3)
(0.3)
(0.2)
(0.3)
CH2
1.2
1.55
1.5
1.6
1.8
1.9
1.8
1.5
1.6
1.6
1.6
1.6
1.7
1.5
1.5
(0.35)
(0.3)
(0.4)
(0.6)
(0.7)
(0.6)
(0.3)
(0.4)
(0.4)
(0.4)
(0.4)
(0.5)
(0.3)
(0.3)
CH
1.6
1.8
1.8
1.8
2.0
1.9
2.1
1.8
2.0
1.8
2.0
2.0
1.9
1.7
1.9
(0.2)
(0.2)
(0.2)
(0.4)
(0.3)
(0.5)
(0.2)
(0.4)
(0.2)
(0.4)
(0.4)
(0.3)
(0.1)
(0.3)
Protons on sp2 and sp Hybridized Carbons
R2C=CH 2
R2C=CHR
RCH=CHR
cyclohexene
ArCH=C-C=O
4.7-5.3
5.1
5.3
5.6
7.7
C=CH-C=O
C=CH-Cl
C=CHBr
CH=CH-C=O
RCH=O
6.0
6.5
6.5
6.9
9.1
R-CC-H
2.3-3.3
R-OH (alcohol)
0.5-5.5
Aromatic hydrogens
6.0-9.0 (mostly 6.7-8.2)
R-NHR (amine)
0.5-5.0
R-C(=O)OH
12-14
R-NH-C(=O)R (amide)
5-8
Nuclear Magnetic Resonance Chemical Shifts
Chemical Shifts in ppm downfield from tetramethylsilane (TMS) (defined as = 0.000 ppm).
General Regions:
0-1
cylopropyl hydrogen s and methyl groups not shifted by electronegative atoms
1 - 2
methyl groups - to O or N atoms, attached to C=C or attached to aromatic rings;
methylene groups
2 - 3
amines
methyl and methylene groups next to carbonyls or attached directly to nitrogen of
3 - 4
groups
methyl and methylene groups attached to oxygen or halogens (Br, Cl). C=CH2
4.5 - 6.5
hydrogens on sp2 hybridized carbons of alkenes (not aromatics)
6.8 - 8.5
aromatic protons
9 - 10
aldehyde protons
IMPORTANT AND DIAGNOSTIC INFRARED BANDS
(a very condensed table)
(cm-1)
Comments
3000-3400
O-H stretching
alcohols- unassociated OH's - 2 bands around 3600 (sharp)
H-bonded - broad absoprtion at 3400
acids- very broad, centred at ca. 3000
3400-3200
N-H stretching
amines- unassociated NH's - 2 bands around 3400 (sharp)
H-bonded - broad absorption at 3200, weaker than OH
3300
C-H stretching of
an acetylene
3100-2850
C-H stretching
2900-2700
C-H stretching of
ALDEHYDE
2250-2100
CC stretching of
ALKYNE
usually weak (weaker than CN), unless
conjugated to C=O
2250-2225
CN stretching of
NITRILE
2250 if not conjugated, 2225 conjugated
Band may be weak
1800
C=O stretching of
ACID CHLORIDE
1735-1740
1710
1700
1660
1650-1600
sp2 - hybridized > 3000; sp3 - hybridized < 3000
>>>>
>>>>
>>>>
C=O stretching of
>>>>
ESTER
>>>>
>>>>
C=O stretching of
>>>>
ALDEHYDE or KETONE >>>>
>>>>
C=O stretching of
>>>>
ACID
>>>>
>>>>
C=O stretching of
>>>>
AMIDE
>>>>
C=C stretch
Conjugation LOWERS these
bands by 30 cm-1
Being in a 5-membered ring
raises these bands by 35 cm-1
may be weak. Intensity increases with conjugation,
especially to C=O
