Chemistry 213
Clark College
Exam 1 SOLUTION
1. Fill in the blank. Predict the product, provide the reagents, or provide the reactants for the following
reactions. Do 7 of 8. You may do the 8th one for extra credit, please indicate which reaction you
would like graded for extra credit. [21 points + 2 EC]
OCH3
OCH3
NO2
HNO3
H2SO4
CH3
The methoxy group is more activating to the ring
than the methyl group, since the oxygen lone
pairs provide an extra resonance structure
stabilizing the carbocation intermediate.
CH3
O
MeO OMe
CH3OH
H+
Acetal formation
O
1) Cl
O2N
A primary C is attached to the
ring, so to prevent carbocation
rearrangement an acylation is
performed, which is followed
by a reduction.
O2N
2) N2H4, KOH, !
or Zn(Hg), HCl
O
PPh3
O
KMnO4, H+, !
OH
Only benzylic carbons with an
H attached will be oxidized.
1
H
H+
O
N
3
O
1) PhMgBr
2) H+
1) NBS, !, ROOR
2) NaCN
Exam 1
2
N
5
The double bond is on the carbonyl
side of the chain when this ring opens.
4
OH
Ph
CN
Spring 2008
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Chemistry 213
Clark College
2. When 3,4-dimethoxybenzaldehyde is brominated with Br2 and FeBr3 only one monobrominated
product is formed. Based on the NMR data provided and your knowledge of benzene reactivity,
determine the structure of the product. Why does this product form preferentially? [10 points]
O
O
H
H3CO
Br
Br2
FeBr3
H
Monobrominated product?
1H-NMR:
OCH3
9.88 ppm, s, 1H
7.53 ppm, s, 1H
7.27 ppm, s, 1H
3.83 ppm, s, 6H
H3CO
OCH3
Only singlets appear in the aromatic region of the NMR, so the bromine must go on the side of the ring
that originally had two hydrogens. To select the ultimate position of the bromine, directing effects of the
original side groups are analyzed. The methoxy groups are o/p directors, whereas the aldehyde is a
meta director. By placing the bromine meta to the aldehyde and ortho to one of the methoxy groups,
the directing effects are maximized and all “awkward” resonance structures in the carbocation
intermediate are avoided.
3. Determine the product and provide the complete, stepwise mechanism for the following reaction.
[15 points]
O
H+
C9H18O2
OH
O
H+
OH
C9H18O2
O
OH
H
OH
Exam 1
H
O
O
OH
O H
OH
Spring 2008
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Chemistry 213
Clark College
4. Road map. Fill in the reagents needed along the following synthetic sequence. [12 points]
NO2
NH2
NO2
conc. H2SO4
HNO3
H2SO4
H2, Ni
SO3H
SO3H
O
H+
H
O
N
H
NH
N
H2, Ni or
a hydride
SO3H reagent
H
H+
SO3H
SO3H
5. When 2-(5-oxopentyl)benzaldehyde reacts with 1 equivalent of ethylene glycol in the presence of
acid, the aldehyde that is not adjacent to the benzene ring is preferentially protected by the glycol.
Explain this result. [8 points]
O
H
H
1 equiv.
OH
HO
H+
O
H
H
O
O
O
2-(5-oxopentyl)benzaldehyde
In the mechanism for acetal formation (reaction of a carbonyl with an alcohol in the presence of acid), a
carbocation intermediate is formed. When this carbocation is adjacent to the aromatic ring, it can be
resonance-delocalized and becomes more stable, thus it is also less reactive.
Exam 1
Spring 2008
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Chemistry 213
Clark College
6. Electrophilic bromination of 3-methoxyfuran produces three isomeric products with the formula
C5H5O2Br. [16 points]
OCH3
Br2
FeBr3
O
Three isomeric products, C5H5O2Br
a. Draw the structures of the three products and rank them with respect to how much of each is
produced (1 = major, 2 = intermediate, 3 = minor).
OCH3
O
Br
OCH3
Br
Br
1
OCH3
O
O
2
3
b. Draw resonance structures of the reaction intermediates and explain the rankings you assigned
in part a.
OCH3
OCH3
Br+
OCH3
Br+
OCH3
Br+
O
Br
O
OCH3
Br
O
Exam 1
Br
O
O
OCH3
O
Br
OCH3
O
OCH3
O
OCH3
Br
O
OCH3
Br
Br
OCH3
Br
O
Br
O
OCH3
O
Spring 2008
Remember, the oxygen has a lone
pair, so it cannot take another bond!
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Chemistry 213
7.
Clark College
Which compound would yield the highest percentage of the meta product upon reaction with CH3Cl
and AlCl3? [3 points]
O
O
O
O
8. What is the IUPAC name of the following compound? [3 points]
OH
Br
Br
a. 2,5-dibromotoluene
c. 3,6-dibromophenol
b. 2,5-dibromophenol
d. 2,5-dibromohydroxybenzene
9. What is the correct structure for m-nitroanisole? [3 points]
NH2
OCH3
OCH3
NO2
NH2
OCH3
O2N
NO2
10. Which of the following molecules is NOT aromatic? [3 points]
O
Exam 1
H
N
Spring 2008
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Chemistry 213
Clark College
11. What is the correct IUPAC name for the following molecule? [3 points]
O
Br
H
O
a. R-2-bromo-5-methyl-4-oxohexanal
c. S-2-bromo-5-methyl-4-oxohexanal
b. S-2-bromo-5-methylhexan-4-on-1-al
d. R-5-bromo-2-methyl-6-oxo-3-hexanone
12. Which of the following reactions will result in enamine formation? [3 points]
H+
a)
O
O
(CH3)2NH
H+
b)
NH2
O
c)
Exam 1
H
(CH3)2NH
H+
N
d)
H+
O
Spring 2008
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