Chemistry 234 Chapter 16 Problem Set
Electrophilic Aromatic Substitution 1) Predict the product and draw the mechanism for electrophile generation for each of the following reactions.
Cl (a) 2 FeCl3
HNO3 (b) H2SO4
SO (c) 3 H2SO4
2) Explain why reaction of benzene with Br2/FeBr3 results in the product bromobenzne instead of 5,6-dibromo-1,3-cyclohexadiene.
3) Predict the product and draw the active electrophile for each reaction shown below.
Cl (a) AlCl3
Cl (b) AlCl3
Cl
O (c) AlCl3
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4) Explain why each of the following substrates do not undergo Freidel-Crafts reactions.
NH2 NO2 N(CH3)3 NH
5) Arrange the following benzene substituents in order of reactivity in electrophilic aromatic substitution reactions. O Cl Ph Ph N Ph Ph
H O N H S Ph N Ph Ph Ph O O
6) Predict the major products when the following benzene derivatives are treated to nitration conditions (HNO3/H2SO4). a. O
Br
b. NH2 Br
c. NO2 Cl
7) Write the full electron pushing mechanism for the nitration of toluene.
Page 2 of 13 Chem. 234 – Chapter 16 Problem Set 8) Predict the product(s) when each of the following benzene derivatives is treated to chloroethane and AlCl3.
a. Br
b. NH2
Cl
c. OH
Br
d. OH Cl
Cl
e. NO2 Cl
Cl
f. Br
Br
g. SO3H
Page 3 of 13 Chem. 234 – Chapter 16 Problem Set 9) Predict the product(s) when the following benzene derivatives are subjected to electrophilic chlorination conditions (Cl2, FeCl3).
a. NO2
O OH
b. OH
NO2
c.
d. SO3H
Br
10) Predict the product(s) for each of the following reactions.
a. O Br O Cl2 H3CO OCH3 FeCl3
b. HNO3
H2SO4 OCH3
c. SO3
H2SO4
d. HO SO3
H2SO4 Br NO2
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11) Predict the product for each benzene side-chain modification reaction shown below. a.
KMnO4
b. H2CrO4
c. NBS light
d. NO2 H2 Pd/C
e. NO2 Sn HCl
f. O Zn(Hg) HCl
g. O N2H2 HO-
12) Propose a synthesis for each of the following compounds starting with benzene.
a. COOH
NO2
COOH
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b. NH2
Cl
c.
Cl Br
NO2
d. O
NO2
Cl
e. COOH
Cl NO2 Br
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f.
Cl NO2
O
g. Br
O2N
Diazonium Ion Reactions 13) Write out the synthetic sequence to prepare phenol and acetanilide (Ph-NHCOCH3) from benzene.
Page 7 of 13 Chem. 234 – Chapter 16 Problem Set 14) Provide syntheses for each of the following compounds, free of other isomers. Your starting material should be benzene in each case.
a. Br
OH
b. I Cl
c. F Br Br
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d.
NC
Nucleophilic Aromatic Substitution 15) For each reaction shown below, determine if the reaction is (a) electrophilic aromatic substitution, (b) Nucleophilic Aromatic Substitution: Addition-Elimination, or (c) Nucleophilic Aromatic Substitution: Benzyne Mechanism. Cl NaOH a. 350 °C
Cl
NaNH2 b. NH3
Cl H C NaNH c. 3 2 NH3
Cl
d. NaOH
NO2
Cl
HNO3 e. H2SO4
Br
NO2 NaOCH3 f.
NO2 Page 9 of 13 Chem. 234 – Chapter 16 Problem Set 16) Show the full electron pushing mechanism for reaction 15c.
17) Show the full electron pushing mechanism for reaction 15d.
18) Explain why the reaction shown below does not occur. Cl OH NaOH Heat O2N NO2 O2N NO2
19) Consider the reaction shown below. Theoretically, there are three possible products. Draw each of these products. In reality only one of these products is formed. Which one is the observed product? Cl Cl OCH3
NO2
Page 10 of 13 Chem. 234 – Chapter 16 Problem Set 20) Show two methods to synthesize the molecule shown below starting with benzene. One route should use diazonium ion chemistry while the other route should not. NO2
OH
21) Show the reaction of phenol with NaOH.
22) Show the reaction of benzoic acid with NaOH.
23) Is phenol or benzoic acid a stronger acid? Explain.
24) Show the reaction of aniline with HCl.
Page 11 of 13 Chem. 234 – Chapter 16 Problem Set 25) Rank the compounds in each set below in order of increasing acidity.
Br O O NH2 OH (a) OH OH
NO OH 2 OH O N OH OH 2 (b)
26) Rank the aniline derivatives below in order of increasing basicity.
NH 2 NH 2 NH2 NH2
O2N O O
Challenge Problems 27) Write a mechanism for the following reaction. Cl O
H H HCl
Page 12 of 13 Chem. 234 – Chapter 16 Problem Set 28) Predict the major product for the reaction of pyrrole with Br2, FeBr3. Hint: use resonance analysis of the intermediate to determine the preferred regioselectivity of the reaction.
H N Br2
FeBr3
29) Show the electron pushing mechanism for the reaction shown below.
OH NaH NO2 O SO2 NO2 SO2
30) Substituted pyridines are known to undergo nucleophilic aromatic substitution via an addition elimination mechanism. Predict the product and show the mechanism for the reaction shown below.
OH N Br
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