Deck 18: Electrophilic Aromatic Substitution

Question 1

What is a major problem with Friedel-Crafts alkylation?

A) It requires high temperatures.
B) The conditions are too acidic.
C) The starting material is frequently over-alkylated.
D) The products coordinate with the aluminum chloride.

Answer 1

The starting material is frequently over-alkylated.

Question 2

What is the electrophile in aromatic sulfonation?

A) H₂SO₃
B) H₂SO₄
C) SO₃⁺
D) HSO₃⁺

Answer 2

HSO₃⁺

Question 3

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Answer 3

III

Question 4

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 5

Why is sulfuric acid used in aromatic nitration?

A) To keep the reaction from getting too basic
B) To form the active electrophile NO₂⁺
C) To protonate the aromatic ring
D) To keep the reaction from getting too acidic

Question 6

What is the electrophile in the Friedel-Crafts alkylation reaction with tert-butylchloride?

A) the tert-butyl cation
B) a complex of tert-butylchloride and aluminum chloride
C) a proton
D) aluminum chloride

Question 7

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 8

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 9

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 10

Why is the nitro group a meta director?

A) Because it is sterically very large.
B) Because it adds electron density to the meta position, thus activating it.
C) Because it stabilizes the intermediate cation.
D) Because it removes more electron density from the ortho and para positions than the meta position, thus deactivating the meta position less.

Question 11

Which of the following statements about the mechanism of electrophilic aromatic substitution is not true?

A) All electrophilic aromatic substitution reactions occur via a two-step mechanism.
B) The transition state of the first step is lower in energy.
C) The first step is the rate-determining step.
D) The second step is the fast step.

Question 12

What are the two effects that have to be considered to determine the influence a substituent will have on electrophilic aromatic substitution?

A) Steric and electronic
B) Inductive and steric
C) Inductive and resonance
D) Resonance and electronic

Question 13

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 14

What is the driving force for losing a proton as the last step in electrophilic aromatic substitution?

A) To neutralize the base that is present
B) To make room for the electrophile
C) To make the ring more reactive
D) To rearomatize the ring system

Question 15

What will be the site that leads to the major mono substitution product for an electrophilic aromatic substitution reaction of the following compound?

A) I
B) II
C) III
D) IV

Question 16

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 17

What is the electrophile in aromatic nitration?

A) NO⁺
B) NO₂⁺
C) NO₃⁺
D) NO₂H

Question 18

What is the first step in the general mechanism for electrophilic aromatic substitution?

A) Protonation of the aromatic ring
B) Deprotonation of the aromatic ring
C) Addition of the electrophile to the aromatic ring
D) Loss of the electrophile from the aromatic ring

Question 19

Which of the following halides will not work as an electrophile in a Friedel-Crafts alkylation reaction?

A) I
B) II
C) III
D) IV

Question 20

What is the major organic product obtained from the following reaction?

A) I
B) II
C) III
D) IV

Question 21

Which of the following substituents are activators in electrophilic aromatic substitution?

A) CH₃O 
B) Cl 
C) NO₂ 
D) HSO₃ 

Question 22

Rank the following deactivating groups in order of increasing deactivating strength, listing the least deactivating first. $$\begin{array} { c c c c } - \mathrm { COOH } & - \mathrm { CHO } & - \mathrm { SO } _ { 3 } \mathrm { H } & - \mathrm { NO } _ { 2 } \\\text { I } & \text { II } & \text { III } & \text { IV }\end{array}$$

A) I < II < III < IV
B) II < III < IV < I
C) II < I < III < IV
D) IV < III < I < II

Question 23

Rank the following activating groups in order of decreasing strength of activation, listing the most activating first. $$\begin{array} { c c c c } \mathrm { H } _ { 3 } \mathrm { C } - & \left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm {~N} - & \mathrm { CH } _ { 3 } \mathrm { O } - & \text { RCOHN- } \\\text { I } & \text { II } & \text { III } & \text { IV }\end{array}$$

A) IV > II > III > I
B) II > III > IV > I
C) III > IV > II > I
D) II > IV > III > I

Question 24

What are the product(s) of the following reaction?

A) Only I and II
B) Only I and III
C) Only II and III
D) Only IV

Question 25

Which of the following substituents is an ortho, para director?

A) " CHO"
B) " COOH"
C) " NHCOR"
D) " CN"

Question 26

Which of the following substituents is a meta director?

A) " N(CH₃)₂"
B) " OCH₃"
C) " NHCOCH₃"
D) " SO₃H"

Question 27

What is (are) the product(s) of the following reaction?

A) Only I
B) Only II
C) Only III
D) Only I and III

Question 28

What are the product(s) of the following reaction?

A) Only I
B) Only II
C) Only I and II
D) Only III

Question 29

Rank the following compounds in order of decreasing reactivity in electrophilic aromatic substitution.

A) II > IV > I > III
B) II > III > IV > I
C) IV > II > I > III
D) IV > I > II > III

Question 30

Which of the following statements about nucleophilic aromatic substitution is not true?

A) Increasing the electronegativity of the halogen increases the reactivity of the aryl halide.
B) Increasing the number of electron-withdrawing groups increases the reactivity of the aryl halide.
C) Electron-withdrawing groups stabilize the intermediate carbanion, and lower the energy of the transition state.
D) When a nitro group is located meta to the halogen, the negative charge of the intermediate carbanion can be delocalized onto the NO₂ group, thus stabilizing it.

Question 31

What is the reactive intermediate formed in the elimination-addition mechanism of nucleophilic aromatic substitution?

A) Carbocation
B) Radical
C) Benzyne
D) Carbanion

Question 32

What is (are) the product(s) of the following reaction?

A) Only I
B) Only II
C) Only III
D) Only I and II

Question 33

How can polyalkylation be minimized in Friedel-Crafts alkylation?

A) Use a large excess of alkyl halide relative to the aromatic compound.
B) Use a large excess of benzene relative to the alkyl halide.
C) Use an alkyl halide without a Lewis acid catalyst.
D) Use a large excess of the Lewis acid catalyst.

Question 34

Which of the following statements about nucleophilic aromatic substitution is true?

A) For the addition-elimination pathway, the nucleophile may become attached either at the site bearing the leaving group or at the site bearing the ortho hydrogen atom.
B) For the elimination-addition pathway, the nucleophile becomes attached only at the site bearing the leaving group.
C) The elimination-addition mechanism is not as common as the addition-elimination mechanism.
D) In the addition-elimination mechanism, the aromatic ring first accepts a pair of electrons from a nucleophile to form a cationic intermediate.

Question 35

Rank the following compounds in order of increasing reactivity in electrophilic aromatic substitution.

A) I < II < III < IV
B) II < I < IV < III
C) III < IV < I < II
D) II < I < III < IV

Question 36

What are the two distinct pathways for nucleophilic aromatic substitution?

A) Addition-substitution and substitution-addition
B) Addition-elimination and elimination-addition
C) Addition-addition and elimination-elimination
D) Elimination-substitution and substitution-elimination

Question 37

Which of the following substituents are deactivators in electrophilic aromatic substitution?

A) HO 
B) CH₃NH 
C) CH₃O 
D) (CH₃)₃N⁺ 

Question 38

What is the major product of the following reaction?

A) I
B) II
C) III
D) IV

Question 39

What is (are) the product(s) of the following reaction?

A) Only I
B) Only II
C) Only III
D) Only I and II

Question 40

What is the reactive intermediate formed in the addition-elimination mechanism of nucleophilic aromatic substitution?

A) Carbocation
B) Radical
C) Benzyne
D) Carbanion

Question 41

What is the product of the following sequence of reactions?

A) I
B) II
C) III
D) IV

Question 42

Which set of reagents would most likely bring about the following transformation?

A) Br₂ and FeBr₃
B) NBS and light
C) Br₂ in CCl₄
D) NaBr and H₂O

Question 43

What is the best choice of reagent to bring about the following transformation?

A) [1] LiAlH₄; [2]H₂O
B) Zn (Hg), HCl
C) NH₃, NaOH
D) H₂, Pd-C

Question 44

What is the product of the following reaction?

A) I
B) II
C) III
D) IV

Question 45

In addition to the product shown, what other product is formed in the following reaction?

A) I
B) II
C) III
D) IV

Question 46

What is the major product of the following reaction?

A) I
B) II
C) III
D) IV

Question 47

What is the product of the following reaction?

A) I
B) II
C) III
D) None of the above

Question 48

Rank the following compounds in order of increasing reactivity in nucleophilic aromatic substitution.

A) III < II < I
B) I < II < III
C) III < I < II
D) I < III < II

Question 49

What is the product of the following reaction?

A) I
B) II
C) III
D) IV

Question 50

What is the best choice of reagent to bring about the following transformation?

A) [1] LiAlH₄; [2] H₂O
B) Zn (Hg), HCl
C) NH₃, NaOH
D) H₂, Pd-C

Question 51

Which aryl fluoride reacts the fastest with NaOH?

A) I
B) II
C) III
D) IV