Chemistry 220b-01
Exam 2 (100 pts)
Tuesday, March 1, 2011
Chapters 12 – 16
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This exam is closed book and closed notes
NOTE: It is difficult for me to give you partial credit if you do not show your work!
Neatness count
Stereochemistry counts are indicated
Good Luck !!
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page 2 of 2
1-14. Multiple choice. Choose the best answer for the following questions (4 pts each, 56 pts)
1.
Which of the following statements about aniline, anisole, acetaniline, and chlorobenzene
is true?
O
NH2
aniline
a)
b)
c)
d)
2.
HN
Cl
acetaniline
chlorobenzene
OCH3
anisole
All will undergo electrophilic aromatic substitution faster than benzene.
All possess ortho/para directing groups.
All are suitable substrates for Friedel-Crafts acylation reactions.
a, b, and c are all true.
Choose the product of the following reaction.
Na, NH3
H3CH2COH
a)
b)
c)
NH2
d)
N
3.
Predict the major product from the electrophilic bromination of 3-nitro-(1-methylethyl)benzene (shown below).
O2N
a)
b)
O2N
c)
Br
Br
O2N
O2N
Br
4.
d)
O2N
Br
Choose the best reagent for the following reaction.
Br
a)
b)
HBr, H2O2
c)
O
N Br ,
O
h!
d)
Br2, FeBr3
Br2, H2O
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page 3 of 3
5.
Which reagent or sequence of reagents will convert benzenediazonium chloride to
cyanobenzene?
Cl
a)
b)
c)
d)
6.
N2+
C N
KCN, AlCl3
NH3
CuCN
1) NBS; 2) NaCN, DMSO
Which of the following sequences is a viable way to synthesize butylbenzene.
O
a)
Zn(Hg), HCl
Cl
AlCl3
b)
c) 2
O
Li
Ph3P:
Br
H
H2, Pd/C
THF
Br
4 Li(0), ether
CuI
Br
then H3O+
d) a, b, and c are all viable sequences to synthesize butylbenzene
7
Which is the best reagent for the following reaction?
O
a)
b)
c)
d)
8.
O
H2, Pd/C
LiAlH4, ether; then HCl
Zn, H3O+
a, b, and c will work equally well
Which reagent or sequence of reagents can be used to synthesize aniline from
benzene?
a)
b)
c)
d)
H2NNH2, KOH, Δ
1) Br2, FeBr3; 2) NH3
1) NaNO2, HCl; 2) Sn, HCl
1) HNO3, H2SO4; 2) H2, Pd/C
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page 4 of 4
9.
Predict the product of the following reaction.
H2Cr2O7, H3O+
OH
OH
a)
O
c)
O
OH
O
OH
b)
OH
H
d)
O
OH
10.
O
O
HO
OH
The most diagnostic spectroscopic method for the presence of an aldehyde is . . .
a) a 1H NMR resonance between δ = 9 – 10 ppm.
b) a 13C NMR resonance between δ = 165 – 220 ppm.
c) an infrared absorbance between 1700 – 1750 cm-1.
d) a weak UV absorbance at 260 nm with a small extinction coefficient (ε).
11.
The carbonyl absorbance in the IR spectrum of cyclohexenone is at 1685 cm-1. Upon
catalytic hydrogenation of cyclohexenone, the carbonyl absorbance of the product . . .
O
H2, Pd/C
a)
b)
c)
d)
12.
. . . is expected at 1685 cm-1.
. . . is expected at 1655 cm-1.
. . . is expected at 1715 cm-1.
. . . is expected to disappear and a new broad absorbance between 3000-3500 cm-1
will be present.
The equilibrium constant for the hydration of butanal is 0.6. The addition of an acid
catalyst . . .
O
H
a)
b)
c)
d)
+ H2O
HO OH
H
. . . will dramatically shift the equilibrium toward the hydrate (Keq is very large).
. . . will dramatically shift the equilibrium toward butanal (Keq is very small).
. . . will result in a 50:50 mixture of butanal and its hydrate (Keq = 1).
. . . does not change the equilibrium (Keq = 0.6).
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page 5 of 5
13.
Which is the best reagent for the oxidation of 1-pentanol to pentanal.
O
OH
a) H2Cr2O7, H3O+
H
b) CrO3, pyridine
c) NaBH4, H3COH
d) O3, then Zn, H2O
14. Choose the major product from the following reaction.
O
H
a)
b)
+
OH
+
Ph3P
c)
d)
15. Provide a suitable starting compound and reagent(s) to prepare the following target
compounds. (12 pts): other answers may be acceptable.
MgBr
O
,THF;
then H3O+
H
HO
NaBH4,
methanol
OH
O
N2+
H2O, !
O
OH
O
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page 6 of 6
16. Provide the major product of the following reactions. (12 pts)
O
O
OCH3
OH
O
O
OCH3
NaBH4, H3COH
H+ catalyst
NH2
+
N
OCH3
OCH3
H3CH2CCl, AlCl3
CH3
CH3
17. Synthesize the target compound below starting from benzene, any primary alkyl halide
(including iodomethane), any organometallic reagent or Wittig reagent derived from a
primary alkyl halide (including iodomethane), any acid chloride, and any inorganic
reagents. Remember, brevity is the soul of wit and organic synthesis (10 pts)
Cl
O
Cl
O
Cl2, FeCl3
AlCl4
O
Cl
PPh3
Cl
other answers may be acceptable
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page 7 of 7
18. Provide a complete mechanism for the acid-catalyzed reaction of cyclohexanone and
methanol to afford 1,1-dimethoxycyclohexane. (10 pts)
O
H+,
H3CO OCH3
H3COH
H X
H
O
H
HO OCH3
O
:X
HO CH3
X H
H
H3CO OCH3
H3C
H2O OCH3
HO OCH3
O
HO CH3
:X
H3CO OCH3
+
H-X
___________________________________________________________________________________
Problem
1-14:_______ (56 pts)
15:_______ (12 pts)
16:_______ (12 pts)
17:_______ (10 pts)
18:_______ (10 pts)
Total out of 100: _________