25.2 electrophilic substitution reactions of benzene Flashcards
what type of mechanism does benzene undergo?
electrophilic substitution
conditions and reagents for the nitration of benzene
- sulfuric acid catalyst
- heated to 50c
- nitric acid
what would happen if the nitration of benzene was taken place at above 50c?
further substitution reactions occurs
how is the electrophile NO2+ formed?
HNO3 + H2SO4 -> NO2+ + HSO4- + H2O
how is the sulfuric acid regenerated?
H+ + HSO4- -> H2SO4
draw the electrophilic substitution reaction of the nitration of benzene
page 438
name the 4 common halogen carriers
- FeCl3
- AlCl3
- AlBr3
- FeBr3
how is the electrophile Br+ formed?
Br2 + FeBr3 -> FeBr4- + Br+
how is the halogen carrier regenerated in the bromination of benzene reaction?
H+ + FeBr4- -> FeBr3 + HBr
draw the electrophilic substitution reaction of the bromination of benzene
page 439
what is an electrophile?
electron pair acceptor
what are the conditions and reagents for the bromination of benzene?
- AlBr3/ FeBr3
- Br2
- room temperature
what are the conditions and reagents for the chlorination of benzene?
- AlCl3/ FeCl3
- Cl2
- room temperature
how is the electrophile Cl+ formed?
Cl2 + FeCl3 -> FeCl4- + Br+
how is the halogen carrier regenerated in the chlorination of benzene reaction?
H+ + FeCl4- -> FeCl3 + HCl
draw the electrophilic substitution reaction of the chlorination of benzene
page 439
what is the alkylation of benzene?
substitution of a hydrogen atom in the benzene ring by an alkyl group
what is alkylation and acylation of benzene also called?
Friedel- Crafts reactions
what is the acylation of benzene?
substitution of a hydrogen atom in the benzene ring by a ketone
what are the conditions and reagents for the alkylation of benzene?
- haloalkane
- halogen carrier
what are the conditions and reagents for the acylation of benzene?
- acyl chloride
- halogen carrier
explain the relative resistance to bromination of benzene compared to alkenes
- 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
draw the electrophilic substitution reaction of the alkylation of benzene
page 440
draw the electrophilic substitution reaction of the acylation of benzene
page 440
