CHEM 211— CHAPTER 16 - Homework
SHORT ANSWER
Consider the Friedel-Crafts alkylation reaction below to answer the following question(s):
1.
Refer to the reaction above. Draw the structure of the electrophilic intermediate in this
reaction.
ANS:
2.
What is the role of the AlCl3 in the reaction at problem 1?
ANS:
The AlCl3 is a Lewis acid catalyst that assists in the ionization of the alkyl halide to give the
carbocation electrophile.
3.
Refer to reaction 1. Write the complete stepwise mechanism for this reaction. Show all
electron flow with arrows and include all intermediate structures.
ANS:
4.
Refer to Exhibit 16-3. Draw all the resonance forms of aniline showing the electrondonating effect of the −NH2 substituent.
ANS:
Exhibit 16-4
1
Chemistry of Benzene: Electrophilic Aromatic Substitution
Consider the reaction below to answer the following question(s).
5.
Refer to Exhibit 16-4. Write the complete stepwise mechanism for the formation of the
ortho product. Show all intermediate structures and show all electron flow with arrows.
ANS:
6.
Refer to Exhibit 16-4. Draw resonance structures for the intermediate carbocation that
explain the directing effect of the −Br.
ANS:
Exhibit 16-5
Rank the compounds in each group below according to their reactivity toward electrophilic
aromatic substitution (most reactive = 1; least reactive = 3). Place the number corresponding to the
compounds' relative reactivity in the blank below the compound.
7.
2
Chapter 16
ANS:
8.
ANS:
8.
At what position, and on what ring, is bromination of phenyl benzoate expected to occur?
Explain your answer.
ANS:
Attack occurs in the activated ring and yields ortho and para bromination.
3
Chemistry of Benzene: Electrophilic Aromatic Substitution
Exhibit 16-6
To answer the following question(s), refer to the data below:
Isobutylbenzene is the starting material for the industrial synthesis of the NSAID, ibuprofen.
9.
Refer to Exhibit 16-6. Attempts to prepare isobutylbenzene by direct Friedel-Crafts
alkylation of benzene result in tert-butylbenzene as the major product. Write the complete
stepwise mechanism for this reaction, showing all electron flow with arrows and showing all
intermediate structures.
ANS:
10.
ANS:
4
Refer to Exhibit 16-6. Propose a synthesis for isobutylbenzene which avoids the problems of
direct Friedel-Crafts alkylation.
Chapter 16
11.
Would you expect (nitromethyl)benzene to be more reactive or less reactive than toluene
toward electrophilic substitution? Explain.
ANS:
(Nitromethyl)benzene should be less reactive than toluene owing to the strong inductive electron
withdrawing effect of the nitro group.
Exhibit 16-7
Consider the reaction below to answer the following question(s).
12.
Refer to Exhibit 16-7. The electrophile in the reaction is:
ANS:
A
13.
Refer to Exhibit 16-7. The Lewis acid catalyst in the reaction is:
ANS:
C
14.
Refer to Exhibit 16-7. This reaction proceeds _____ (faster or slower) than benzene.
ANS:
slower
15.
Refer to Exhibit 16-7. Draw the structure of product D.
ANS:
5
Chemistry of Benzene: Electrophilic Aromatic Substitution
16.
The following reaction proceeds by an intramolecular nucleophilic aromatic substitution
mechanism. Write the complete stepwise mechanism, showing all intermediate structures
and all electron flow with arrows.
ANS:
17.
On the structural intermediates below, show all electron flow with arrows for the
nucleophilic aromatic substitution reaction of p-nitrochlorobenzene with KOH.
ANS:
Exhibit 16-8
Give the major organic product(s) of each of the following reactions. If none is predicted, write
"N.R."
6
Chapter 16
18.
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19.
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20.
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21.
7
Chemistry of Benzene: Electrophilic Aromatic Substitution
ANS:
22.
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23.
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24.
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8
Chapter 16
25.
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26.
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27.
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9
Chemistry of Benzene: Electrophilic Aromatic Substitution
28.
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29.
ANS:
(Friedel-Crafts reactions do not proceed in the presence of a deactivating group)
30.
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31.
ANS:
10
Chapter 16
Exhibit 16-9
Choose the best reagent(s) from the list provided below for carrying out the following conversions.
Place the letter of the reagent in the box beside the reaction number over the arrow. There is only
one answer for each reaction.
a.
b.
c.
d.
e.
KMnO4, H3O+
Br2, FeBr3
Cl2, FeCl3
CH3Cl, AlCl3
HNO3, H2SO4
f.
g.
h.
i.
j.
ClCO(CH2)2CH3, AlCl3
CH3CH2CH2CH2Cl, AlCl3
H2/Pd
NBS, peroxides
(CH3)3CCH2Cl
32.
ANS:
33.
ANS:
11
Chemistry of Benzene: Electrophilic Aromatic Substitution
34.
ANS:
35.
ANS:
12