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Organic Chemistry

John McMurry

Chapter 16

Chemistry of Benzene: Electrophilic Aromatic Substitution - all with Video Answers

Educators

Chapter Questions

02:26

Problem 1

Monobromination of toluene gives a mixture of three bromotoluene products. Draw and name them.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:12

Problem 2

Propose a mechanism for the electrophilic fluorination of benzene with F-TEDA-BF $_{4}.$

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:55

Problem 3

How many products might be formed on chlorination of $o$ -xylene (o-dimethylbenzene), $m$ -xylene, and $p$ -xylene?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:57

Problem 4

When benzene is treated with $\mathrm{D}_{2} \mathrm{SO}_{4}$, deuterium slowly replaces all six hydrogens in the aromatic ring. Explain.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:58

Problem 5

Which of the following alkyl halides would you expect to undergo Friedel-Crafts reaction with rearrangement and which without? Explain.
(a) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}$
(b) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{Cl}) \mathrm{CH}_{3}$
(c) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl}$
(d) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCH}_{2} \mathrm{Cl} \quad$
(e) Chlorocyclohexane

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
01:50

Problem 6

What is the major monosubstitution product from the Friedel-Crafts reaction of benzene with 1-chloro-2-methylpropane in the presence of Alcl_?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
01:32

Problem 7

Identify the carboxylic acid chloride that might be used in a Friedel-Crafts acylation reaction to prepare each of the following acylbenzenes: (a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:39

Problem 8

Rank the compounds in each of the following groups in order of their reactivity to electrophilic substitution:
(a) Nitrobenzene, phenol, toluene, benzene
(b) Phenol, benzene, chlorobenzene, benzoic acid
(c) Benzene, bromobenzene, benzaldehyde, aniline

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:56

Problem 9

Predict the major products of the following reactions:
(a) Nitration of bromobenzene
(b) Bromination of nitrobenzene
(c) Chlorination of phenol
(d) Bromination of aniline

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:57

Problem 10

Use Figure 16.11 to explain why Friedel-Crafts alkylations often give polysubstitution but Friedel-Crafts acylations do not. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:54

Problem 11

An electrostatic potential map of (trifluoromethyl)benzene, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CF}_{3},$ is shown. Would you expect (trifluoromethyl)benzene to be more reactive or less reactive than toluene toward electrophilic substitution? Explain. (FIGURE CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:27

Problem 12

Acetanilide is less reactive than aniline toward electrophilic substitution. Explain. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:49

Problem 13

Draw resonance structures for the intermediates from reaction of an electrophile at the ortho, meta, and para positions of nitrobenzene. Which intermediates are most stable?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:10

Problem 14

At what position would you expect electrophilic substitution to occur in each of the following substances?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:03

Problem 15

Show the major product(s) from reaction of the following substances with (1) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}$, $\mathrm{AlCl}_{3}$ and $(2) \mathrm{HNO}_{3}, \mathrm{H}_{2} \mathrm{SO}_{4}.$
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:21

Problem 16

The herbicide oxyfluorfen can be prepared by reaction between a phenol and an aryl fluoride. Propose a mechanism. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:40

Problem 17

Treatment of $p$ -bromotoluene with $\mathrm{NaOH}$ at $300^{\circ} \mathrm{C}$ yields a mixture of two products, but treatment of $m$ -bromotoluene with NaOH yields a mixture of three products. Explain.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:02

Problem 18

What aromatic products would you obtain from the KMnO_ oxidation of the following substances?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:29

Problem 19

Refer to Table 6.3 on page 204 for a quantitative idea of the stability of a benzyl radical. How much more stable (in kj/mol) is the benzyl radical than a primary alkyl radical? How does a benzyl radical compare in stability to an ally| radical?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:52

Problem 20

Styrene, the simplest alkenylbenzene, is prepared commercially for use in plastics manufacture by catalytic dehydrogenation of ethylbenzene. How might you prepare styrene from benzene using reactions you've studied? (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:20

Problem 21

How would you prepare diphenylmethane, $(P h)_{2} C H_{2}$, from benzene and an acid chloride?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
11:02

Problem 22

How might you synthesize the following substances from benzene?
(a) $m$ -Chloronitrobenzene
(b) $m$ -Chloroethylbenzene
(c) $4-$ Chloro-1-nitro-2-propylbenzene
(d) 3-Bromo-2-methylbenzenesulfonic acid

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:21

Problem 23

In planning a synthesis, it's as important to know what not to do as to know what to do. As written, the following reaction schemes have flaws in them. What is wrong with each?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:28

Problem 24

Draw the product from reaction of each of the following substances with (1) $\mathrm{Br}_{2}, \mathrm{FeBr}_{3}$ and $(2) \mathrm{CH}_{3} \mathrm{COCl}, \mathrm{AlCl}_{3}.$
(a)(FIGURE CAN'T COPY) (b)(FIGURE CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:11

Problem 25

The following molecular model of a dimethyl-substituted biphenyl represents the lowest-energy conformation of the molecule. Why are the two benzene rings tilted at a $63^{\circ}$ angle to each other rather than being in the same plane so that their $p$ orbitals can overlap? Why doesn't complete rotation around the single bond joining the two rings occur? (FIGURE CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:24

Problem 26

How would you synthesize the following compound starting from benzene? More than one step is needed. (FIGURE CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:39

Problem 27

The following compound can't be synthesized using the methods discussed in this chapter. Why not? (FIGURE CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:02

Problem 28

Identify each of the following groups as an activator or deactivator and as an o, $p$ -director or $m$ -director:
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY) (d)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:30

Problem 29

Predict the major product(s) of nitration of the following substances. Which react faster than benzene, and which slower?
(a) Bromobenzene
(b) Benzonitrile
(c) Benzoic acid
(d) Nitrobenzene
(e) Benzenesulfonic acid
(f) Methoxybenzene

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:36

Problem 30

Rank the compounds in each group according to their reactivity toward electrophilic substitution.
(a) Chlorobenzene, $o$ -dichlorobenzene, benzene
(b) $p$ -Bromonitrobenzene, nitrobenzene, phenol
(c) Fluorobenzene, benzaldehyde, $o$ -xylene
(d) Benzonitrile, $p$ -methylbenzonitrile, $p$ -methoxybenzonitrile

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
10:03

Problem 31

Predict the major monoalkylation products you would expect to obtain from reaction of the following substances with chloromethane and AlCl_3:
(a) Bromobenzene
(b) $m$ -Bromophenol
(c) $p$ -Chloroaniline
(d) 2,4 -Dichloronitrobenzene
(e) 2,4 -Dichlorophenol
(f) Benzoic acid
(g) $p$ -Methylbenzenesulfonic acid
(h) $2,5-$ Dibromotoluene

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
08:48

Problem 32

Name and draw the major product(s) of electrophilic chlorination of the following compounds:
(a) $m$ -Nitrophenol
(b) $o$ -Xylene
(c) $p$ -Nitrobenzoic acid
(d) $p$ -Bromobenzenesulfonic acid

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
05:26

Problem 33

Predict the major product(s) you would obtain from sulfonation of the following compounds:
(a) Fluorobenzene
(b) $m$ -Bromophenol
(c) obenzene
(d) $2,4-$ Dibromophenol

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:25

Problem 34

Rank the following aromatic compounds in the expected order of their reactivity toward Friedel-Crafts alkylation. Which compounds are unreactive?
(a) Bromobenzene
(b) Toluene
(c) Phenol Aniline $\quad$
(e) Nitrobenzene
(f) $p$ -Bromotoluene

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:26

Problem 35

What product(s) would you expect to obtain from the following reactions?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY) (d)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:44

Problem 36

Predict the major product(s) of the following reactions:
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY) (d)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
01:51

Problem 37

Aromatic iodination can be carried out with a number of reagents, including iodine monochloride, ICl. What is the direction of polarization of ICl? Propose a mechanism for the iodination of an aromatic ring with ICl.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:47

Problem 38

The sulfonation of an aromatic ring with $\mathrm{SO}_{3}$ and $\mathrm{H}_{2} \mathrm{SO}_{4}$ is reversible. That is, heating benzenesulfonic acid with $\mathrm{H}_{2} \mathrm{SO}_{4}$ yields benzene. Show the mechanism of the desulfonation reaction. What is the electrophile?

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:52

Problem 39

The carbocation electrophile in a Friedel-Crafts reaction can be generated in ways other than by reaction of an alkyl chloride with AlCl_s. For example, reaction of benzene with 2 -methylpropene in the presence of $\mathrm{H}_{3} \mathrm{PO}_{4}$ yields tertbutylbenzene. Propose a mechanism for this reaction.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:37

Problem 40

The $N, N, N$ -trimethylammonium group, $-\mathrm{N}\left(\mathrm{CH}_{3}\right)_{3},$ is one of the few groups that is a meta-directing deactivator yet has no electron-withdrawing resonance effect. Explain.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:39

Problem 41

The nitroso group, $-\mathrm{N}=\mathrm{O},$ is one of the few nonhalogens that is an orthoand para-directing deactivator. Explain by drawing resonance structures of the carbocation intermediates in ortho, meta, and para electrophilic reaction on nitrosobenzene, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{N}=\mathrm{O}.$

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
08:05

Problem 42

Triphenylmethane can be prepared by reaction of benzene and chloroform in the presence of AlCl_. Propose a mechanism for the reaction. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:12

Problem 43

Using resonance structures of the intermediates, explain why bromination of biphenyl occurs at ortho and para positions rather than at meta. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:02

Problem 44

Benzene and alkyl-substituted benzenes can be hydroxylated by reaction with $\mathrm{H}_{2} \mathrm{O}_{2}$ in the presence of an acidic catalyst. What is the structure of the reactive electrophile? Propose a mechanism for the reaction. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
11:15

Problem 45

How would you synthesize the following substances starting from benzene or phenol? Assume that ortho-and para-substitution products can be separated.
(a) $o$ -Bromobenzoic acid
(b) $p$ -Methoxytoluene
(c) 2,4,6 -Trinitrobenzoic acid
(d) $m$ -Bromoaniline

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:15

Problem 46

Starting with benzene as your only source of aromatic compounds, how would you synthesize the following substances? Assume that you can separate ortho and para isomers if necessary.
(a) $p$ -Chloroacetophenone
(b) $m$ -Bromonitrobenzene
(c) o-Bromobenzenesulfonic acid
(d) $m$ -Chlorobenzenesulfonic acid

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:30

Problem 47

Starting with either benzene or toluene, how would you synthesize the following substances? Assume that ortho and para isomers can be separated.
(a) 2 -Bromo- 4 -nitrotoluene
(b) 1,3,5 -Trinitrobenzene
(c) 2,4,6 -Tribromoaniline
(d) $m$ -Fluorobenzoic acid

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:13

Problem 48

As written, the following syntheses have flaws. What is wrong with each?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
05:15

Problem 49

At what position and on what ring do you expect nitration of 4-bromobiphenyl to occur? Explain, using resonance structures of the potential intermediates. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
07:48

Problem 50

Electrophilic substitution on 3 -phenylpropanenitrile occurs at the ortho and para positions, but reaction with 3 -phenylpropenenitrile occurs at the meta position. Explain, using resonance structures of the intermediates. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:16

Problem 51

Addition of HBr to 1-phenylpropene yields only (1-bromopropyl)benzene. Propose a mechanism for the reaction, and explain why none of the other regioisomer is produced. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:23

Problem 52

At what position, and on what ring, would you expect the following substances to undergo electrophilic substitution?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY) (d)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:40

Problem 53

At what position, and on what ring, would you expect bromination of benzanilide to occur? Explain by drawing resonance structures of theintermediates. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:37

Problem 54

Would you expect the Friedel-Crafts reaction of benzene with $(R)$ - 2 -chlorobutane to yield optically active or racemic product? Explain.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
09:16

Problem 55

How would you synthesize the following substances starting from benzene?
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY) (c)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:14

Problem 56

The compound MON-0585 is a nontoxic, biodegradable larvicide that is highly selective against mosquito larvae. Synthesize MON-0585 using either benzene or phenol as a source of the aromatic rings. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
10:56

Problem 57

Hexachlorophene, a substance used in the manufacture of germicidal soaps, is prepared by reaction of 2,4,5 -trichlorophenol with formaldehyde in the presence of concentrated sulfuric acid. Propose a mechanism for the reaction. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:24

Problem 58

Benzenediazonium carboxylate decomposes when heated to yield $\mathrm{N}_{2}, \mathrm{CO}_{2}$ and a reactive substance that can't be isolated. When benzenediazonium carboxylate is heated in the presence of furan, the following reaction is observed: (EQUATION CAN'T COPY) What intermediate is involved in this reaction? Propose a mechanism for its formation.

Tom Rutherford
Tom Rutherford
Numerade Educator
04:43

Problem 59

Phenylboronic acid, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{B}(\mathrm{OH})_{2},$ is nitrated to give $15 \%$ ortho-substitution product and $85 \%$ meta. Explain the meta-directing effect of the $-B(O H)_{2}$ group.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:42

Problem 60

Draw resonance structures of the intermediate carbocations in the bromination of naphthalene, and account for the fact that naphthalene undergoes electrophilic substitution at C1 rather than C2. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:49

Problem 61

Propose a mechanism for the reaction of 1 -chloroanthraquinone with methoxide ion to give the substitution product 1 -methoxyanthraquinone. Use curved arrows to show the electron flow in each step. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:29

Problem 62

4-Chloropyridine undergoes reaction with dimethylamine to yield 4-dimethylaminopyridine. Propose a mechanism for the reaction. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
04:42

Problem 63

$p$ -Bromotoluene reacts with potassium amide to give a mixture of $m$ - and $p$ -methylaniline. Explain.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
08:44

Problem 64

Propose a mechanism to account for the reaction of benzene with $2,2,5,5-$ tetramethyltetrahydrofuran. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
08:30

Problem 65

Propose a mechanism to account for the following reaction: (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
12:18

Problem 66

In the Gatterman-Koch reaction, a formyl group (-CHO) is introduced directly onto a benzene ring. For example, reaction of toluene with CO and HCl in the presence of mixed CuCl/AlCl$_{3}$ gives p-methylbenzaldehyde. Propose a mechanism. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:33

Problem 67

Treatment of $p$ -tert-butylphenol with a strong acid such as $\mathrm{H}_{2} \mathrm{SO}_{4}$ yields phenol and 2 -methylpropene. Propose a mechanism.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
07:47

Problem 68

How would you synthesize the following compounds from benzene? Assume that ortho and para isomers can be separated.
(a)(EQUATION CAN'T COPY) (b)(EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:12

Problem 69

You know the mechanism of HBr addition to alkenes, and you know the effects of various substituent groups on aromatic substitution. Use this knowledge to predict which of the following two alkenes reacts faster with HBr. Explain your answer by drawing resonance structures of the carbocation intermediates. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:52

Problem 70

Benzyl bromide is converted into benzaldehyde by heating in dimethyl sulfoxide. Propose a structure for the intermediate, and show the mechanisms of the two steps in the reaction. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
02:26

Problem 71

Use your knowledge of directing effects, along with the following data, to deduce the directions of the dipole moments in aniline and bromobenzene. (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
03:00

Problem 72

Identify the reagents represented by the letters a-e in the following scheme: (EQUATION CAN'T COPY)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
09:12

Problem 73

Phenols (ArOH) are relatively acidic, and the presence of a substituent group on the aromatic ring has a large effect. The $\mathrm{p} K_{\mathrm{a}}$ of unsubstituted phenol, for example, is $9.89,$ while that of $p$ -nitrophenol is $7.15 .$ Draw resonance structures of the corresponding phenoxide anions and explain the data.

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator
06:02

Problem 74

Would you expect $p$ -methylphenol to be more acidic or less acidic than unsubstituted phenol? Explain. (See Problem 16.73.)

Matthew Lueckheide
Matthew Lueckheide
Numerade Educator