reactions of arenes
DESCRIPTION
Reactions of arenes. L.O.: Outline the mechanism of nitration. Outline the mechanism of of acylation. Identify the reactive intermediates involved in nitration and acylation. Name the mechanisms of both reactions. STRUCTURE OF BENZENE. STRUCTURE OF BENZENE. STRUCTURE OF BENZENE. NITRATION. - PowerPoint PPT PresentationTRANSCRIPT
Reactions of arenes
L.O.:
Outline the mechanism of nitration. Outline the mechanism of of acylation. Identify the reactive intermediates involved
in nitration and acylation. Name the mechanisms of both reactions.
C C
C
CC
C HH
H H
H H
STRUCTURE OF BENZENE
STRUCTURE OF BENZENE
STRUCTURE OF BENZENE
NITRATION
+ HNO3 + H2O
NO2
nitrobenzene
Conditions conc HNO3
conc H2SO4 catalyst
50ºC
-H+
Formation of electrophile
HNO3
+ 2 H2SO4 + 2 HSO4-
+ H3O+
NO2
+
Reaction of electrophile with aromatic compound
NO2
NO2+ NO2
+H
nitronium ion
NITRATION – ELECTROPHILIC SUBSTITUTION
NITRATION
Equation (name product)
Conditions
Mechanism
CH3CH3
NO2
NITRATION
2-methylnitrobenzene
Conditions conc HNO3
conc H2SO4 catalyst
50ºC
CH3
+ HNO3 + H2O
CH3
NO2
NITRATION
Uses of nitro compounds:
1) as explosives
2) to make aromatic amines (used to make dyes)
CH3
NO2
NO2
O2N
1,3,5-trinitrotolueneTNT
Name the mechanism for this reaction.
Electrophilic substitution
Draw the electron arrangement (dot-cross diagram) of aluminium chloride.
FRIEDEL-CRAFTS ACYLATION
aromatic ketone
Conditions AlCl3 catalyst
R C
O
Cl+
CR O
+ HCl
+
CR O
+ R C
O
O C
O
R R C
O
OH
FRIEDEL-CRAFTS ACYLATION
WARNING! - do not mix
Friedel-Crafts acylation & other acylations
(needs AlCl3)
Swap H on benzene ring
for acyl group
H H N
H
R
H O R
Swap H on O/N
for acyl group
FRIEDEL-CRAFTS ACYLATION
WARNING! - Classic question to test this
NH2 NHCOCH3
CH3COCl
H replaced is on N not benzene ring.
This is NOT Friedel-Crafts acylation!
Formation of electrophile
AlCl3
+ RCOCl +
AlCl4–+
C
O
R
acylium ion
OR
AlCl3
+ R-C-O-C-R +
–
+
C
O
R
acylium ion
O
O R-C-O-AlCl3
O
FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION
-H+
Reaction of electrophile with aromatic compound
CC
+H+
C
O
R
O
RO
R
FRIEDEL-CRAFTS ACYLATION – ELECTROPHILIC SUBSTITUTION
AlCl4– + H+ AlCl3 + HCl
+ H+ + AlCl3– R-C-O-AlCl3
O
R-C-OH
O
or
Regeneration of catalyst
Equation
Conditions
Mechanism
FRIEDEL-CRAFTS ACYLATION
CH3CH3
CO CH2CH3
Conditions AlCl3 catalyst
FRIEDEL-CRAFTS ACYLATION
CH3
CO CH2CH3
CH3
+ CH3CH2 C
O
Cl+ HCl