Electrophilic Aromatic Substitution Reactions

Question 1

Does bromination of benzene occur at room temperature?

Answer 1

No

Question 2

Name a catalyst for the bromination of benzene

Answer 2

Iron (3) bromide FeBr3

Question 3

What reagents are used in the nitration of benzene and why?

Answer 3

Concentrated nitric and sulfuric acids

• To obtain a nitronium ion
• sulfuric acid acts as a catalyst

Question 4

Name the reagents in the reduction of a nitro group(addition of hydrogens)

Answer 4

Zinc, tin or iron

Aqueous HCl

Question 5

Name a use for the reduction of of a nitro group

Answer 5

Is the best method for adding an amino group to the ring in the production of many dyes and pharmaceutical agents

Question 6

How much faster does toluene react than benzene and why?

Answer 6

25 times faster, methyl group is an activator

Question 7

Explain the effects of alkyl groups in reactions of benzene

Answer 7

They are activating substituents and ortho and para directors

Question 8

Explain the effects of alkyl groups in reactions of benzene

Answer 8

The inductive effect- alkyl groups can increase electron density to the ring via the sigma bond making the molecule more active

Question 9

In nucleophile aromatic substitution, what determines where the nucleophile attacks

Answer 9

Where the leaving group is

Question 10

In electrophilic aromatic substitution, what determines where the electrophile attacks?

Answer 10

Electronic and steric factors( mix of ortho and para products)

Question 11

Name one limitation of friended-Crafts reaction that limits its reagents

Answer 11

F-C reactions only work with benzene, activated benzene derivatives and halobenzene, failing on deactivated benzene rings as they are less reactive

Question 12

Are F-C reactions susceptible to carbocation reagents?

Answer 12

Yes

Question 13

Is the alkylbenzene formed by the F-C reaction more reactive than benzene and what is the consequence?

Answer 13

Yes, causing polyalkylation to occur

Question 14

Name the catalyst for the bromination of benzene and its purpose

Answer 14

FeBr3 - makes Br2 more electrophile by reacting with it to give Br+ and FeBr4-

Question 15

Describe the carbocation intermediate between benzene and Br+

Answer 15

It is not aromatic, doubly allylic and is a hybrid of 3 resonance forms

Question 16

Name the reagents for silfonation of benzene

Answer 16

Benzene

Sulfate ( SO3)

Catalyst: sulfuric acid

Product: benzenesulfonic acid

Question 17

Name one use of the sulfonation of benzene

Answer 17

Key step in the synthesis of compounds such as the sulfa drug family

Question 18

What are the catalysts of the desulfonation reaction?

Answer 18

H+ and heat( can be accomplished by heating dilute sulfuric acid)

Question 19

Name the activators of benzene in order of strength

Answer 19

Phenoxides (O-), anilines, phenols( OH attached), phenyl ethers ( O-R group attached), anilides, alkylbenzenes

Question 20

Name the deactivated groups for benzene

Answer 20

Nitro group, sulfonic group, cyano group, ketones or aldehydes, ester, quaternary ammonium

Question 21

What do all activators have in common?

Answer 21

Are either R groups, or have an N or O atom with a lone pair directly bond to the benzene ring(electron- donor groups)

Question 22

What do all deactivators have in common?

Answer 22

All deactivators are either halogens, have in atom with partial or full positive charge bonded directly to the ring( electron withdrawing groups)

Question 23

How does CN affect orientation of a reaction?

Answer 23

CN is a meta director

Question 24

How does OH affect the orientation of a reaction?

Answer 24

OH is an ortho and para director

Question 25

Is benzoic acid more or less reactive than benzene?

Answer 25

Benzoic acid is less reactive than benzene

Question 26

Which are usually stronger directors? Activating groups or deactivating groups?

Answer 26

Activating groups?

Question 27

What is another term for dimeyhylbenzene?

Answer 27

Xylene

Question 28

How do halogens change the orientation of a reaction?

Answer 28

Ortho and para directing

Question 29

How do all deactivators except halogens affect the orientation of a reaction?

Answer 29

Meta directors

Question 30

What kind of directors are all activating groups?

Answer 30

Ortho and para

Question 31

How do alkyl groups affect reactivity of benzene( describe the process)

Answer 31

The inductive effect- alkyl groups donate to the electron density to the ring through the sigma bond, making it more reactive