CHEM 232 • Exam Two • April 5, 2010
Name_____________________(-1 pt)
TA Name___________________(-1 pt) UIN_________________(-1 pt)
Question 1 [Qualitative Ranking, 40 points]
A significant amount of time has been devoted to describing the physical and chemical properties of organic compounds including
acidity, bond strength, boiling point, solubility, heat of combustion, conformation, constitution and reactivity. Rank the molecules in
each set below according to the trends observed for the physical and chemical properties indicated.
A. Rank each of the following alkyl halides in order of increasing rate of SN2 substitution (1 = slowest rate; 5 = fastest rate). (5 pts)
Br
4
3
1
Br
Br
Br
F
2
5
B. 1,3-Dienes and dienophiles undergo Diels-Alder cycloaddition to form cyclohexenes. Rank the following diene/dienophile
combinations in order of decreasing rate of reaction (1 = fastest reaction, 4 = slowest reaction). (4 pts)
OMe
O
O
O
OMe
OMe
OMe
OMe
OMe
O
O
1
3
4
2
C. Rank the rate of SN1 substitution in each of the solvents below in increasing order (1 = slowest SN1 reaction, 5 = fastest SN1
reaction). (5 pts)
O
O
Me
Me
Me
O
H
H
O
H
CH2Cl2
H
O
H
(ε = 21)
(ε = 33)
(ε = 78)
(ε = 9)
(ε = 58)
2
3
5
1
4
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CHEM 232 • Exam Two • April 5, 2010
Name_____________________(-1 pt)
TA Name___________________(-1 pt) UIN_________________(-1 pt)
D. Rank the following molecules in order of increasing number of chiral centers dipole moment (µ) (1 = lowest dipole moment, 4 =
highest dipole moment). (5 pts)
OH
HO
HO
OH
OH
OH
E.
OH
OH
4
F
FF
HO
F
H
2
5
F
F
F
F
OH
H
F
FF
F
3
1
Rank the following anions in order of decreasing leaving group ability (1 = best leaving group; 5 = poorest leaving group). (5
pts)
O
H3C S O
O
Me O
F
2
O
F3C S O
O
4
Cl
1
5
3
F. Based on your knowledge of the periodic table (see final page), rank each compound/anion in order of increasing nucleophilicity
(1 = least nucleophilic; 5 = most nucleophilic) (5 pts)
O
O
O- Na+
Se- Na+
1
O- Na+
5
S- Na+
S- Na+
4
2
3
G. Rank the following molecules in order of increasing heat of combustion (1 = least exothermic, lowest ∆Hcomb, 6 = most
exothermic, highest ∆Hcomb). (6 pts)
3
5
6
4
1
2
H. Rank the following carbocations in order of decreasing stability (1 = most stable, 5 = least stable). (5 pts)
H
H
H
3
H
2
H
H
H
H
5
4
Page 2 of 8
H
1
CHEM 232 • Exam Two • April 5, 2010
Name_____________________(-1 pt)
TA Name___________________(-1 pt) UIN_________________(-1 pt)
Question 2 [Predict-the-Products, 50 points, 5 points each] Draw the major organic product(s) for each of the reaction schemes
below. Indicate charged atoms. For Brφnsted acid-base reactions, draw both conjugates.
O
O
OMe
+
O
OMe
heat
CN
NC
OMe
or
Na
CN
NH3(l)
single isomer
single isomer
1. Pd/CaCO3
lead acetate
quinoline
H
MeO
Br
OH
MeO
O
H
Cl
HCl
light (hv)
F
H
-78 °C
Br
2 x HF
O
Me
O
or
O
2.
2. BH3•THF, then
H2O2/NaOH
Br2
O
1. t-BuOK
F
TsO
OTs
Na2S
(S2- anion)
S
C9H18S
CH3
TsO
H
H
CH3
CH3
CH3
MeS- Na+
EtOH
H
SMe
H
CH3
Br2
Br
Br
CH3
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Br
or
Br
Question 3 [Mechanisms, 40 points]
A. Draw a reasonable arrow-pushing mechanism for the following transformation. (10 pts)
Cl Me
Me
H
H
H
HCl
H
H
HO
H
HO
B. For the following first order nucleophilic substitution (SN1) reaction, draw a reasonable arrow-pushing mechanism. Account for
why this transformation proceeds with 66% net inversion rather than racemization (10 + 5 pts)
H
Br
EtOH, H2O
H
OH
HO
H
+
(S)-2-bromooctane (1)
(S)-octan-2-ol (2)
(R)-octan-2-ol (3)
17% yield
83% yield
Page 4 of 8
A. Draw a reasonable arrow-pushing mechanism for the following transformation. (15 pts)
HN
CF3
Cl
1
1. HBr
HN
OH
2. H2O
CF3
Cl
2
Page 5 of 8
Question 4 [Synthesis, 40 points; 15 + 25 points] Devise a synthesis for both target molecules (products) below. Write the forward
synthesis from the reactant(s). Include all necessary conditions above/below the reaction arrow for each transformation. Write out the
product for each transformation in your synthesis separately. You may write out a retrosynthetic analysis; however, only the forward
synthesis will be graded. More than one synthesis may be possible for each
?
Br
OH
Cl
NaOH, NaOEt
or tert-BuOK
Br
H
?
HO
MsCl or TsCl
pyridine
HO
RSO2O
or
NaBr
HO
Br
H2SO4
H
Na+ -NH2
Br
or
RSO2O
H2, Pd-CaCO3
lead acetate
quinoline
Page 6 of 8
Cl2
OH
H 2O
Cl
Question 5 [Stereochemistry & Structure, 40 points]
A.
(i) Mark all the chirality centers in the structures of the naturally-occuring cell migration inhibitor Moverastin (1), the anticancer agent
puraquinonic acid (2) and the lipid-lowering drug Lipitor (3) with an asterisk (*). (10 pts)
(ii) Using the Cahn–Ingold–Prelog (CIP) priority rules, determine the absolute configuration and assign an R or S descriptor to each
chirality center within molecules 1, 2, and 3. (14 pts)
S
*R
O
OH
R
HO
*
*
*
O R
R
NH
R
HO
HO
N
* *
O
*O
O
CHO
OH
OH OH O
R
F
Moverastin (1)
(-)-Puraquinonic Acid (2)
Lipitor (3)
B. Which of the following molecules are chiral, which are achiral?. (8 pts)
Cl
H O H
Cl
CO2H
Cl
HO
Cl
Cl
HO
Cl
achiral
chiral
O
OH
OH
HO
O
achiral
Me
chiral
C. What isomeric relationship do the following pairs of compounds have with each other? (12 pts)
H
O
and
(a)
(c)
O
O
enantiomers
enantiomers
OH
and
O
H
OH
(d)
(b)
and
OH
OH
and
OH
OH
diastereomers
conformers
Page 7 of 8
OH
Question 6 [Functional Groups, 30 points; 5 points each] Write the name for the principle functional group present in each molecule
(e.g. ketone, alcohol, etc.). Do not write the IUPAC name or common name for the molecule, just the functional group name. Names
must be spelled correctly for credit.
O
O
Cl
acid chloride
H
aldehyde
OH
H
C
NO2
H
enol
allene
H
N
nitro group
amine
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