25.2 electrophilic substitution reactions of benzene

Question 1

what type of mechanism does benzene undergo?

Answer 1

electrophilic substitution

Question 2

conditions and reagents for the nitration of benzene

Answer 2

• sulfuric acid catalyst
• heated to 50c
• nitric acid

Question 3

what would happen if the nitration of benzene was taken place at above 50c?

Answer 3

further substitution reactions occurs

Question 4

how is the electrophile NO2+ formed?

Answer 4

HNO3 + H2SO4 -> NO2+ + HSO4- + H2O

Question 5

how is the sulfuric acid regenerated?

Answer 5

H+ + HSO4- -> H2SO4

Question 6

draw the electrophilic substitution reaction of the nitration of benzene

Answer 6

page 438

Question 7

name the 4 common halogen carriers

Answer 7

• FeCl3
• AlCl3
• AlBr3
• FeBr3

Question 8

how is the electrophile Br+ formed?

Answer 8

Br2 + FeBr3 -> FeBr4- + Br+

Question 9

how is the halogen carrier regenerated in the bromination of benzene reaction?

Answer 9

H+ + FeBr4- -> FeBr3 + HBr

Question 10

draw the electrophilic substitution reaction of the bromination of benzene

Answer 10

page 439

Question 11

what is an electrophile?

Answer 11

electron pair acceptor

Question 12

what are the conditions and reagents for the bromination of benzene?

Answer 12

• AlBr3/ FeBr3
• Br2
• room temperature

Question 13

what are the conditions and reagents for the chlorination of benzene?

Answer 13

• AlCl3/ FeCl3
• Cl2
• room temperature

Question 14

how is the electrophile Cl+ formed?

Answer 14

Cl2 + FeCl3 -> FeCl4- + Br+

Question 15

how is the halogen carrier regenerated in the chlorination of benzene reaction?

Answer 15

H+ + FeCl4- -> FeCl3 + HCl

Question 16

draw the electrophilic substitution reaction of the chlorination of benzene

Answer 16

page 439

Question 17

what is the alkylation of benzene?

Answer 17

substitution of a hydrogen atom in the benzene ring by an alkyl group

Question 18

what is alkylation and acylation of benzene also called?

Answer 18

Friedel- Crafts reactions

Question 19

what is the acylation of benzene?

Answer 19

substitution of a hydrogen atom in the benzene ring by a ketone

Question 20

what are the conditions and reagents for the alkylation of benzene?

Answer 20

• haloalkane

- halogen carrier

Question 21

what are the conditions and reagents for the acylation of benzene?

Answer 21

• acyl chloride

- halogen carrier

Question 22

explain the relative resistance to bromination of benzene compared to alkenes

Answer 22

• In benzene, pi-bond(s) are delocalised 
• In alkenes, pi-bond is localised between two carbons
• benzene has a lower electron density
• alkene/C=C has a higher electron density 
• benzene polarises bromine less

Question 23

draw the electrophilic substitution reaction of the alkylation of benzene

Answer 23

page 440

Question 24

draw the electrophilic substitution reaction of the acylation of benzene

Answer 24

page 440