Organic Chemistry

Paula Yurkanis Bruice

Chapter 16 Reactions of Substituted Benzenes - all with Video Answers

Educators

Chapter Questions

01:23

Problem 1

Name the following compounds:

Lottie Adams

Numerade Educator

02:40

Problem 2

Draw structures of the following compounds:
a. para-toluidine
b. meta-cresol
c. para-xylene
d. ortho-chlorobenzenesulfonic acid

Temi Ajayi

Numerade Educator

02:49

Draw the structure of each of the following compounds:
a. $m$ -chlorotoluene
b. $p$ -bromophenol
c. $ o$ -nitroaniline
d. $m$ -chlorobenzonitrile
e. 2 -bromo- 4 -iodophenol
f. $m$ -dichlorobenzene
g. 2,5 -dinitrobenzaldehyde
h. $o$ -xylene

Temi Ajayi

Numerade Educator

04:28

Problem 4

Correct the following incorrect names:
a. 2,4,6 -tribromobenzene
b. 3-hydroxynitrobenzene
c. para-methylbromobenzene
d. 1,6 -dichlorobenzene

Temi Ajayi

Numerade Educator

04:39

Problem 5

Give the product of each of the following reactions:

Temi Ajayi

Numerade Educator

08:42

Problem 6

Show how the following compounds could be prepared from benzene:
a. benzaldehyde
b. styrene
c. 1 -bromo- 2 -phenylethane
d. 2-phenyl-1-ethanol
e. aniline
f. benzoic acid

Temi Ajayi

Numerade Educator

05:23

Problem 7

For each of the following substituents, indicate whether it donates electrons inductively, withdraws electrons inductively, donates electrons by resonance, or withdraws electrons by resonance (inductive effects should be compared with a hydrogen; remember that many substituents can be characterized in more than one way):
a. $\mathrm{Br}$
b. $\mathrm{CH}_{2} \mathrm{CH}_{3}$
c.
d. $\mathrm{NHCH}_{3}$
e. $\mathrm{OCH}_{3}$
f. $^{+} N\left(C H_{3}\right)_{3}$

Temi Ajayi

Numerade Educator

04:10

Problem 8

List the members of the following sets of compounds in order of decreasing reactivity toward electrophilic aromatic substitution:
a. benzene, phenol, toluene, nitrobenzene, bromobenzene
b. dichloromethylbenzene, difluoromethylbenzene, toluene, chloromethylbenzene

Temi Ajayi

Numerade Educator

04:42

Problem 9

Explain why the halo-substituted benzenes have the relative reactivities shown in Table 16.1
Table 16.1 shows that fluorine is the least deactivating of the halogen substituents and iodine is the most deactivating. We know that fluorine is the most electronegative of the halogens, which means that it is best at withdrawing electrons inductively. Fluorine is also best at donating electrons by resonance because its $2 p$ orbital- compared with the $3 p$ orbital of chlorine, the $4 p$ orbital of bromine, or the $5 p$ orbital of iodine $-$ can better overlap with the $2 p$ orbital of carbon. So the fluorine substituent is best both at donating electrons by resonance and at withdrawing electrons inductively. Because the table shows that fluorine is the weakest deactivator of the halogens, we can conclude that electron donation by resonance is the more important factor in determining the relative reactivities of halo-substituted benzenes.

Temi Ajayi

Numerade Educator

06:33

Problem 10

a. Draw the resonance contributors for nitrobenzene.
b. Draw the resonance contributors for chlorobenzene.

Temi Ajayi

Numerade Educator

06:10

Problem 11

What product(s) would result from nitration of each of the following compounds?
a. propylbenzene
b. bromobenzene
c. benzaldehyde
d. benzenesulfonic acid
e. cyclohexylbenzene
f. benzonitrile

Rashmi Sinha

Numerade Educator

03:52

Problem 12

Are the following substituents ortho-para directors or meta directors?
a. $\mathrm{CH}_{2}=\mathrm{CHC} \equiv \mathrm{N}$
b. $\mathrm{NO}_{2}$
c. $\mathrm{CH}_{2} \mathrm{OH}$
d. $\operatorname{COOH}$
e. $\mathrm{CF}_{3}$
f. $\mathrm{N}=\mathrm{O}$

Temi Ajayi

Numerade Educator

06:09

Problem 13

Which of the compounds in each of the following pairs is more acidic?

Temi Ajayi

Numerade Educator

03:58

Problem 14

$p$ -Nitrophenol has a $\mathrm{p} K_{\mathrm{a}}$ of $7.14,$ whereas the $\mathrm{p} K_{\mathrm{a}}$ of $m$ -nitrophenol is $8.39 .$ Explain.

Temi Ajayi

Numerade Educator

02:45

Problem 15

Give the products, if any, of each of the following reactions:
a. benzonitrile $+$ methyl chloride $+\mathrm{AlCl}_{3}$
b. aniline $+3 \mathrm{Br}_{2}$
c. benzoic acid $+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}+\mathrm{AlCl}_{3}$
d. benzene $+2 \mathrm{CH}_{3} \mathrm{Cl}+\mathrm{AlCl}_{3}$

Temi Ajayi

Numerade Educator

03:37

Problem 16

When $N, N$ -dimethylaniline is nitrated, some meta -nitro- $N, N$ -dimethylaniline is formed. Why does the meta isomer form? (Hint: The $\mathrm{p} K_{\mathrm{a}}$ of $N, N$ -dimethylaniline is $5.07,$ and more meta isomer is formed if the reaction is carried out at $\mathrm{pH}=3.5$ than if it is carried out at $\mathrm{pH}=4.5 .)$

Temi Ajayi

Numerade Educator

13:12

Problem 17

Show how each of the following compounds can be synthesized from benzene:
a. $p$ -chloroaniline
b. $m$ -chloroaniline
c. $p$ -nitrobenzoic acid
d. $m$ -nitrobenzoic acid
e. $m$ -bromopropylbenzene
f. $ o$ -bromopropylbenzene
g. 1-phenyl-2-propanol
h. 2 -phenylpropene

Temi Ajayi

Numerade Educator

03:38

Problem 18

Give the major product(s) of each of the following reactions:
a. nitration of $p$ -fluoroanisole
b. chlorination of $o$ -benzenedicarboxylic acid
c. bromination of $p$ -chlorobenzoic acid

Temi Ajayi

Numerade Educator

02:30

Problem 19

When phenol is treated with $\mathrm{Br}_{2},$ a mixture of monobromo-, dibromo- - and tribromophenols is obtained. Design a synthesis that would convert phenol primarily to orthobromophenol.
The bulky sulfonic acid group will add preferentially to the para position. Both the OH and SO $_{3} \mathrm{H}$ groups will direct bromine to the position ortho to the OH group.

Temi Ajayi

Numerade Educator

02:02

Problem 20

Explain why a diazonium group on a benzene ring cannot be used to direct an incoming substituent to the meta position.

Zubair Abdulla

Numerade Educator

02:59

Problem 21

Explain why HBr should be used to generate the benzenediazonium salt if bromobenzene is the desired product of the Sandmeyer reaction and HCI should be used if chlorobenzene is the desired product.

Temi Ajayi

Numerade Educator

02:10

Problem 22

Write the sequence of steps involved in the conversion of benzene into benzenediazonium chloride.

Temi Ajayi

Numerade Educator

14:54

Problem 23

Show how the following compounds could be synthesized from benzene:
a. $m$ -dibromobenzene
b. $m$ -bromophenol
c. $o$ -chlorophenol
d. $m$ -nitrotoluene
e. $p$ -methylbenzonitrile
f. $m$ -chlorobenzaldehyde

Temi Ajayi

Numerade Educator

02:56

Problem 24

In the mechanism for electrophilic aromatic substitution with a diazonium ion as the electrophile, why does nucleophilic attack occur on the terminal nitrogen atom of the diazonium ion rather than on the nitrogen atom bonded to the benzene ring?

Temi Ajayi

Numerade Educator

03:39

Problem 25

Give the structure of the activated benzene ring and the diazonium ion used in the synthesis of the following compounds:
a. butter yellow
b. methyl orange
(The structures of these compounds can be found in Section $8.12 .$ )

Temi Ajayi

Numerade Educator

02:22

Problem 26

What products would be formed from the reaction of isopropylamine with sodium nitrite and aqueous HCl?

Temi Ajayi

Numerade Educator

02:16

Problem 27

Diazomethane can be used to convert a carboxylic acid into a methyl ester. Propose a mechanism for this reaction.

Zubair Abdulla

Numerade Educator

03:30

Problem 28

Draw resonance contributors for the carbanion that would be formed if meta-chloronitrobenzene could react with hydroxide ion. Why doesn't it react?

Temi Ajayi

Numerade Educator

03:07

Problem 29

a. List the following compounds in order of decreasing reactivity toward nucleophilic aromatic substitution:
chlorobenzene
1-chloro-2,4-dinitrobenzene
$p$ -chloronitrobenzene
b. List the same compounds in order of decreasing reactivity toward electrophilic aromatic substitution.

Temi Ajayi

Numerade Educator

07:18

Problem 30

Show how each of the following compounds could be synthesized from benzene:
a. $\quad o$ -nitrophenol
b. $p$ -nitroaniline
c. $p$ -bromoanisole

Temi Ajayi

Numerade Educator

07:23

Problem 31

Starting with benzene, show how meta-aminoanisole could be prepared via a synthesis that
a. involves a benzyne intermediate
b. does not involve a benzyne intermediate

Temi Ajayi

Numerade Educator

04:45

Problem 32

Give the products that would be obtained from the reaction of the following compounds with sodium amide in liquid ammonia:

Temi Ajayi

Numerade Educator

01:50

Problem 33

Use the resonance contributors of naphthalene to predict whether all the carbon-carbon bonds have the same length, as they do in benzene.

Dan Ni

Numerade Educator

04:15

Problem 34

Draw the resonance contributors for the carbocation intermediates obtained from electrophilic aromatic substitution at the 1 -position and the 2 -position of naphthalene. Use the resonance contributors to explain why substitution at the 1 -position is preferred.

Temi Ajayi

Numerade Educator

02:39

Problem 35

Give the products that would be obtained from the reaction of the following compounds with $\mathrm{Cl}_{2}$ :

Temi Ajayi

Numerade Educator

02:56

Problem 36

Draw the structure of each of the following compounds:
a. $m$ -ethylphenol
b. $p$ -nitrobenzenesulfonic acid
c. $\quad(E)-2$ -phenyl- 2 -pentene
d. $\quad o$ -bromoaniline
e. 2 -chloroanthracene
f. $m$ -chlorostyrene
g. $\quad o$ -nitroanisole
h. 2,4 -dichlorotoluene

Temi Ajayi

Numerade Educator

01:23

Problem 37

Name the following compounds:

Lottie Adams

Numerade Educator

06:19

Problem 38

Provide the necessary reagents next to the arrows.

Temi Ajayi

Numerade Educator

07:30

Problem 39

The $\mathrm{p} K_{\mathrm{a}}$ values of a few ortho- $,$ meta-, and para-substituted benzoic acids are shown here:
The relative $p K_{\mathrm{a}}$ values depend on the substituent. For chloro-substituted benzoic acids, the ortho isomer is the most acidic and the para isomer is the least acidic; for nitro-substituted benzoic acids, the ortho isomer is the most acidic and the meta isomer is the least acidic; and for amino-substituted benzoic acids, the meta isomer is the most acidic and the ortho isomer is the least acidic. Explain these relative acidities.
$\mathrm{Cl}:$ ortho $>$ meta $>$ para
$\mathrm{NO}_{2}^{\mathrm{t}}$ ortho $>$ para $>$ meta
$\mathrm{NH}_{2}$ : meta $>$ para $>$ ortho

Temi Ajayi

Numerade Educator

07:59

Problem 40

Give the product(s) of each of the following reactions:
a. benzoic acid $+\mathrm{HNO}_{3} / \mathrm{H}_{2} \mathrm{SO}_{4}$
b. isopropylbenzene $+$ cyclohexene $+\mathrm{HF}$
c. naphthalene $+$ acetyl chloride $+\mathrm{AlCl}_{3}$ followed by $\mathrm{H}_{2} \mathrm{O}$
d. $\quad o$ -methylaniline $+$ benzenediazonium chloride
e. cyclohexyl phenyl ether $+\mathrm{Br}_{2} / \mathrm{FeBr}_{3}$
f. phenol $+\mathrm{H}_{2} \mathrm{SO}_{4}+\Delta$
g. ethylbenzene $+\mathrm{Br}_{2} / \mathrm{FeBr}_{3}$
h. $m$ -xylene $+\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+\mathrm{H}^{+}+\Delta$

Temi Ajayi

Numerade Educator

02:25

Problem 41

Rank the following anions in order of decreasing basicity:

Ronald Prasad

Numerade Educator

04:11

Problem 42

The compound with the following 1 H NMR spectrum is known to be highly reactive toward electrophilic aromatic substitution. Identify the compound.

Temi Ajayi

Numerade Educator

10:45

Problem 43

Show how the following compounds could be synthesized from benzene:
a. $m$ -chlorobenzenesulfonic acid
b. $m$ -chloroethylbenzene
c. benzyl alcohol
d. $m$ -bromobenzonitrile
e. 1 -phenylpentane
f. $m$ -hydroxybenzoic acid
g. $m$ -bromobenzoic acid
h. $p$ -cresol

Temi Ajayi

Numerade Educator

03:53

Problem 44

For each of the groups of substituted benzenes, indicate
a. the one that would be the most reactive in an electrophilic aromatic substitution reaction
b. the one that would be the least reactive in an electrophilic aromatic substitution reaction
c. the one that would yield the highest percentage of meta product

Temi Ajayi

Numerade Educator

08:33

Problem 45

Arrange the following groups of compounds in order of decreasing reactivity toward electrophilic aromatic substitution:
a. benzene, ethylbenzene, chlorobenzene, nitrobenzene, anisole
b. $1-$ chloro- 2,4 -dinitrobenzene, 2,4 -dinitrophenol, 2,4 -dinitrotoluene
c. toluene, $p$ -cresol, benzene, $p$ -xylene
d. benzene, benzoic acid, phenol, propylbenzene
e. $p$ -nitrotoluene, 2 -chloro- 4 -nitrotoluene, 2,4 -dinitrotoluene, $p$ -chlorotoluene
f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Temi Ajayi

Numerade Educator

04:34

Problem 46

Give the products of the following reactions:

Ricajoy Montero

Numerade Educator

06:10

Problem 47

For each of the statements in Column I, choose a substituent from Column II that fits the description for the compound at the right:
Column I
a. $\mathrm{Z}$ donates electrons inductively, but does not donate or withdraw electrons by resonance.
b. $\underline{Z}$ withdraws electrons inductively and withdraws electrons by resonance.
c. Z deactivates the ring and directs ortho-para.
d. $\underline{Z}$ withdraws electrons inductively, donates electrons by resonance, and activates the ring.
e. $\mathrm{Z}$ withdraws electrons inductively, but does not donate or withdraw electrons by resonance.
Column II
$\mathrm{OH}$
$\mathrm{Br}$
$^{+} \mathrm{NH}_{3}$
$\mathrm{CH}_{2} \mathrm{CH}_{3}$
$\mathrm{NO}_{2}$

Temi Ajayi

Numerade Educator

06:35

Problem 48

For each of the following compounds, indicate the ring carbon that would be nitrated if the compound were treated with $\mathrm{HNO}_{3} / \mathrm{H}_{2} \mathrm{SO}_{4}:$

Zubair Abdulla

Numerade Educator

14:54

Problem 49

Show how the following compounds could be synthesized from benzene:
a. $N, N, N$ -trimethylanilinium iodide
b. benzyl methyl ether
c. $p$ -benzylchlorobenzene
d. 2 -methyl- 4 -nitrophenol
e. $p$ -nitroaniline
f. $m$ -bromoiodobenzene
g. $p$ -dideuteriobenzene
h. $p$ -nitro- $N$ -methylaniline

Temi Ajayi

Numerade Educator

02:53

Problem 50

Which of the following compounds will react with HBr more rapidly?

Ronald Prasad

Numerade Educator

03:36

Problem 51

Give the product(s) obtained from the reaction of each of the following compounds with $\mathrm{Br}_{2} / \mathrm{FeBr}_{3}$ :

Temi Ajayi

Numerade Educator

03:06

Problem 52

Which would react more rapidly with $\mathrm{Cl}_{2}+\mathrm{FeCl}_{3}, m$ -xylene or $p$ -xylene? Explain.

Temi Ajayi

Numerade Educator

03:14

Problem 53

What products would be obtained from the reaction of the following compounds with $\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+\mathrm{H}^{+}+\Delta ?$

Temi Ajayi

Numerade Educator

04:23

Problem 54

A student had prepared three ethyl-substituted benzaldehydes, but had neglected to label them. The premed student at the next bench said that they could be identified by brominating a sample of each and determining how many bromo-substituted products were formed. Is the premed student's advice sound?

Temi Ajayi

Numerade Educator

03:20

Problem 55

Explain, using resonance contributors for the intermediate carbocation, why a phenyl group is an ortho-para director.

Zubair Abdulla

Numerade Educator

04:25

Problem 56

When heated with an acidic solution of sodium dichromate, compound A forms benzoic acid. Identify compound A from its 'H NMR spectrum.

Temi Ajayi

Numerade Educator

05:41

Problem 57

Describe two synthetic routes for the preparation of $p$ -methoxyaniline with benzene as the starting material.

Temi Ajayi

Numerade Educator

03:13

Problem 58

Which is a more stable intermediate?

Temi Ajayi

Numerade Educator

02:30

Problem 59

If phenol is allowed to sit in $\mathrm{D}_{2} \mathrm{O}$ that contains a small amount of $\mathrm{D}_{2} \mathrm{SO}_{4},$ what products would be formed?

Temi Ajayi

Numerade Educator

09:39

Problem 60

Show how the following compounds could be prepared from benzene:

Temi Ajayi

Numerade Educator

03:45

Problem 61

An unknown compound reacts with ethyl chloride and aluminum trichloride to form a compound that has the following $^{1} \mathrm{H}$ NMR spectrum. Give the structure of the compound.

Temi Ajayi

Numerade Educator

11:04

Problem 62

How could you distinguish among the following compounds, using
a. their infrared spectra?
b. their $^{1} \mathrm{H}$ NMR spectra?

Temi Ajayi

Numerade Educator

03:04

Problem 63

The following tertiary alkyl bromides undergo an $S_{N} 1$ reaction in aqueous acetone to form the corresponding tertiary alcohols. List the alkyl bromides in order of decreasing reactivity.

Temi Ajayi

Numerade Educator

03:50

Problem 64

$p$ -Fluoronitrobenzene is more reactive than $p$ -chloronitrobenzene toward hydroxide ion. What does this tell you about the ratedetermining step for nucleophilic aromatic substitution?

Temi Ajayi

Numerade Educator

04:38

Problem 65

a. Explain why the following reaction leads to the products shown:
b. What product would be obtained from the following reaction?

Zubair Abdulla

Numerade Educator

09:53

Problem 66

Describe how mescaline could be synthesized from benzene. The structure of mescaline is given on p. 622 .

Zubair Abdulla

Numerade Educator

05:52

Problem 67

Propose a mechanism for the following reaction that explains why the configuration of the asymmetric carbon in the reactant is retained in the product:

Zubair Abdulla

Numerade Educator

06:26

Problem 68

Explain why hydroxide ion catalyzes the reaction of piperidine with 2,4 -dinitroanisole, but has no effect on the reaction of piperidine with 1-chloro-2,4-dinitrobenzene.

Zubair Abdulla

Numerade Educator