Arenes:

1
Arenes compounds containing both aliphatic and
aromatic parts. Alkylbenzenes Alkenylbenzenes Alky
nylbenzenes Etc. Emphasis on the effect that one
part has on the chemistry of the other
half. Reactivity orientation
2
Example ethylbenzene EAS in the aromatic
part -CH2CH3 activates and directs ortho-
para-
Free radical halogenation in the side
chain -C6H5 activates and directs benzyl
3
Alkylbenzenes, nomenclature Special names
4
others named as alkylbenzenes
5
Use of phenyl C6H5- phenyl
do not confuse phenyl (C6H5-) with benzyl
(C6H5CH2-)
6
Alkenylbenzenes, nomenclature
7
Alkynylbenzenes, nomenclature
8
Alcohols, etc., nomenclature
9

• Alkylbenzenes, syntheses
• Friedel-Crafts alkylation
• Modification of a side chain
• a) addition of hydrogen to an alkene
• b) reduction of an alkylhalide
• i) hydrolysis of Grignard reagent
• ii) active metal and acid
• c) Corey-House synthesis

10
Modification of side chain
11
Friedel-Crafts Ar-H R-X, AlCl3 ?
Ar-R HX Ar-H R-OH, H ? Ar-R
H2O Ar-H alkene, H ? Ar-R
12
(No Transcript)
13
(No Transcript)
14

• Friedel-Crafts limitations
• Polyalkylation
• Possible rearrangement
• R-X cannot be Ar-X
• NR when the benzene ring is less reactive than
  bromobenzene
• NR with -NH2, -NHR, -NR2 groups

15
polyalkylation
The alkyl group activates the ring making the
products more reactive that the reactants leading
to polyalkylation. Use of excess aromatic
compound minimizes polyalkylation in the lab.
16
The electrophile in Friedel Crafts alkylation is
a carbocation R-X AlX3 ? R R-OH
H ? R C C
H ? R Carbocations can rearrange! ?
17
rearrangement
18
(No Transcript)
19
R-X cannot be Ar-X
20
NR with rings less reactive than bromobenzene
-CHO, -COR -SO3H -COOH, -COOR -CN -NR3 -NO2
21
NR with NH2, -NHR, -NR2
22

• Friedel-Crafts limitations
• Polyalkylation
• Possible rearrangement
• R-X cannot be Ar-X
• NR when the benzene ring is less reactive than
  bromobenzene
• NR with -NH2, -NHR, -NR2 groups
• In syntheses it is often best to do
  Friedel-Crafts alkylation in the first step!

23

• Alkylbenzenes, reactions
• Reduction
• Oxidation
• EAS
• a) nitration
• b) sulfonation
• c) halogenation
• d) Friedel-Crafts alkylation
• Side chain
• free radical halogenation

24
Alkylbenezenes, reduction
CH3CH3
NR NR NR
NR
H2, Ni
H2, Ni 300oC, 100 atm.
25
Alkylbenezenes, oxidation
CH3CH3
NR NR NR
NR NR
KMnO4
KMnO4 heat
26
(No Transcript)
27
Oxidation of alkylbenzenes. 1) Syn 2)
identification C8H10
28
Alkylbenzenes, EAS
-R is electron releasing. Activates to EAS and
directs ortho/para
29
Alkylbenzenes, free radical halogenation in side
chain benzyl free radical
30
(No Transcript)
31

• Alkenylbenzenes, syntheses
• Modification of side chain
• a) dehydrohalogenation of alkyl halide
• b) dehydration of alcohol
• c) dehalogenation of vicinal dihalide
• d) reduction of alkyne
• (2. Friedel-Crafts alkylation)

32
Alkenylbenzenes, synthesis modification of side
chain
33
Alkenylbenzenes, synthesis Friedel-Crafts
alkylation not normally used for
alkenylbenzenes. an exception
34
(No Transcript)
35

• Alkenylbenzenes, reactions
• Reduction
• Oxidation
• EAS
• Side chain
• a) addn of H2 h) oxymercuration
• b) addn of X2 i) hydroboration
• c) addn of HX j) addition of free rad.
• d) addn of H2SO4 k) addn of carbenes
• e) addn of H2O l) epoxidation
• f) addn of X2 H2O m) hydroxylation
• g) allylic halogenation n) ozonolysis
• o) vigorous oxidation

36
Alkenylbenzenes, reactions reduction
37
Alkenylbenzenes, reactions oxidation
38
Alkenylbenzenes, reactions EAS?
39
(No Transcript)
40
Alkenylbenzenes, reactions side chain
41
Benzyl carbocation
42
(No Transcript)
43
(No Transcript)
44
100 syn-oxidation make a model!
45
Alkynylbenzenes, syntheses Dehydrohalogenation
of vicinal dihalides
46

• Alkynylbenzenes, reactions
• Reduction
• Oxidation
• EAS
• Side chain
• a) reduction e) as acids
• b) addn of X2 f) with Ag
• c) addn of HX g) oxidation
• d) addn of H2O, H

47
Alkynylbenzenes, reactions reduction
anti- syn-
48
Alkynylbenzenes, reactions oxidation
49
Alkynylbenzenes, reactions EAS?
50
Alkynylbenzenes, reactions side chain
51
(No Transcript)
52
Arenes alkylbenzenes alkenylbenzenes alkyny
lbenzenes As expected, but remember that you
cannot do EAS on alkenyl- or alkynylbenzenes.