Transcript Polynuclear Hydrocarbons

Polynuclear Hydrocarbons
Classification
of
Polynuclear Hydrocarbons
Polynuclear Hydrocarbons may be
divided into two groups,
Polynuclear Hydrocarbons
Benzenoid
Isolated
Non- Benzenoid
Fused rings
Linear
Azulene
Angular
Biphenyl
Naphthalene
Phenanthrene
I.
Isolated Ring
Polynuclear
Hydrocarbons
Biphenyl (diphenyl):
Preparation of Biphenyl
a) Fittig reaction
2Ph-Br + 2Na
ether
soln
Ph-Ph + 2NaBr
b) From benzene diazonium sulphate
N=N HSO4
Cu
EtOH
+ N2 + CuHSO4
Biphenyl
c) From benzidine
H2N
NH2
Benzidine
H3PO4
Biphenyl
NaNO2
HCl
Cl N=N
N=N Cl
d) Ulmann diaryl synthesis
2 Cu
Ph-Ph + 2CuI
2 Ph-I
2 Cu
2 H3C
I
H3C
sealed tube
CH3
4,4'- Dimethyl-biphenyl
NO2
NO2
2 Cu
2
I
sealed tube
O2N
2,2'- Dinitro-biphenyl
e) By using Arylmagnesium
halide
C OC l
PhMgBr + PhBr
2
Ph-Ph + MgBr2
Reactions of biphenyl
Biphenyl undergoes
substitution reactions,
• In biphenyl one ring act as electron
donating group and the other act as
electron withdrawing group
Resonance shows that O- and P- are the most reactive positions
towards electrophilic substitution.
The electrophilic substitution occurs in 4- position (major) and
2- position (minor) due to steric effect of other benzene ring.
The 2nd substitution occurs in the empty ring in 2 or 4- position.
e.g.
NO2
conc HNO3
conc H2SO4
NO2
+
2-Nitro-biphenyl
4-Nitro-biphenyl
conc HNO3
conc H2SO4
NO2
O2N
NO2 +
4,4'-Dinitro-biphenyl
NO2
NO2 +
2,4'-Dinitro-biphenyl
O2N
2,2'-Dinitro-biphenyl
Problem: Explain the
products formed when
biphenyl is mononitrated and
when it is dinitrated.
Biphenyl derivatives
(1) Benzidine (4, 4`-diaminobiphenyl)
H2N
(2) Diphenic acid
NH2
COOH COOH
(3) Diphenyl methane
CH2
(1) Benzidine
(4, 4' diaminobiphenyl)
Methods of preparation
From dihydrazo benzene
NH-NH
Hydrazano-benzene
HCl
H2N
NH2
Benzidine
Q. Show how could you prepare benzidine
from benzene?
 Answer
I
I
conc. HNO3
I2
conc. H2SO4
HNO3
NO2
I
Cu
2
O2N
NO2
NO2
H2N
NH2
Benzidine
Zn/HCl
Uses of Benzidine
 preparation of Congo red
H2N
NH2
NaNO2/HCl
Cl N N
N N Cl
NH2
NH2
NH2
2
NN
SO3H
N N
SO3H
SO3H
Congo Red
(2) Diphenic acid
Methods of preparation
From anthranilic acid
NH2
COOH COOH
COOH
COOH
NaNO2
HCl
N N

Cu
biphenyl- 2,2'- dicarboxylic acid
(Diphenic acid)
Ulmann diaryl synthesis
COOEt COOEt
COOEt
2
I

Cu
COOH COOH
HCl
biphenyl- 2,2'- dicarboxylic acid
(Diphenic acid)
oxidation of Phenanthrene or
phenanthraquinone
COOH
50% H2O2
AcOH, 
phenanthrene
COOH
Diphenic acid
O
K2Cr2O7
H2SO4
O
phenanthraquinone
Chemical Reactions
1. with acetic anhydride
O
COOH
Ac2O
O
COOH
O
Diphenic acid
Diphenic anhydride
2. Conversion of diphenic acid
to
dflourenone
COOH
Ca(OH)2
O
C O
C O
COOH
Diphenic acid
O
Ca diphenate
Ca

80-200C
-CaCO3
O
9- fluorenone
3. with conc. H2SO4
COOH
O
Free
rotation
COOH
Diphenic acid
O
OH
conc. H2SO4 HOOC
-H2O
O
OH
9- fluorenone- 4carboxylic acid
4. Oxidation of KMnO4
COOH
KMnO4
COOH
Diphenic acid
COOH
COOH
pthalic acid
5. with sodalime
COOH
Sodalime
COOH
Diphenic acid
biphenyl
Atropisomers of biphenyl
 Optical isomers produced due to
restricted rotation is called atropisomers
 Restricted rotation produce when 0position contains two different bulky
groups and hence molecule is optically
active.. for example
CO2H NO2
Mirror
NO2 CO2H
NO2 CO2H
CO2H NO2
Cl
H
H
Cl
Mirror
H
Cl
H2N
H
B
A
Optically active
NO2
CO2H Cl
CO2H CO2H
Optically active
no plane of symmetry
Optically active
NO2
CO2H NO
2
Optically active
no plane of symmetry
 When o- position contains two similar groups, the
molecule is optically inactive due to presence of plane
of symmetry .. for example
HO2C
CO2H
H3OC
CO2H
H3OC
NO2
Plane of symmetry
O2N
CO2H
Optically inactive due to presence of plane of symmetry
COOH
O2N
HO2C
NO2
Optically active
free rotation is possible
NO2
F
Optically active
F is a small atom so permit
by free rotation
(3) Diphenyl methane
Methods of preparation
1. Friedel- Crafte
CH2Cl
+
AlCl3
Benzyl chloride
2
+
CH2
Diphenyl methane
CH2Cl2
AlCl3
CH2
Diphenyl methane
2. From benzophenone
O
HI/ P

or Zn Hg/ HCl
or NH2NH2/ NaOEt
Benzophenone
CH2
Diphenyl methane
Chemical Reactions
1. Nitration
CH2
conc. HNO2
conc. H2SO4
Diphenyl methane
conc. HNO2
conc. H2SO4
CH2
NO2
1-benzyl-4-nitrobenzene
O2 N
CH2
bis(4- nitrophenyl)methane
NO2
2. Halogenation
Br
CH2
Diphenyl methane
Br2
hv
C
H
Diphenylmethylbromide
3. Oxidation
O
CH2
Diphenyl methane
[O]
K2Cr2O7
H2SO4
C
benzophenone
II. Fused System
a) Naphthalene
OH


8
1

7
2


6
3

4
5


1-Naphthol or -Naphthol
Br
OH
2-Naphthol or -Naphthol
Br
HO3S
1,8- Dibromo-naphthalene
SO3H
Naphthalene-2,7- disulfonic acid
Structure elucidation of
naphthalene
1- Molecular Formula: C6H8
COOH
2- Naphthalene
O
COOH
Phthalic acid
C
So naphthalene contain the skeleton
C
NO2
COOH
3-
Naphthalene
nitration
Nitronaphthalene
O
COOH
Nitrophthalic acid
So nitro group is present in benzene ring
Naphthalene nitration
4-
Nitronaphthalene
redn.
aminonaphthalene
O
COOH
COOH
Phthalic acid
The benzene ring in phthalic acid produced by
oxidation of aminonaphthalene is not the same
ring is that obtained by oxidation of
nitronaphthalene.
i.e. Naphthalene contains two benzene rings and
we can explain this by this equation
A
B
HNO3
NH2
NO2
NO2
COOH
HOOC
B
HOOC
O
A
B
redn.
A
B
O
A
COOH
The structure of naphthalene is confirmed by
method of its analysis
1- Howarth method
O
O
+
O
AlCl3
Zn-Hg/HCl
HO
R
R
Zn-Hg/HCl
R
R
O
O
O
O
Succinic anhydride
conc.H2SO4
-H2O
HO
R
Se

R
Other way of cyclization
O
O
+
O
SOCl2
AlCl3
HO
R
R
Zn-Hg/HCl
intramoluclar
Friedel Craft R
R
O
O
O
O
Succinic anhydride
AlCl3
Cl
R
Se

R
 The reaction occurs if R is o- or p- directing
group such as NH2, NHR, OH, OR, R,
halogen.
 If R is m- directing group (e.g. NO2, CN,
COOH, COCH3, SO3H) no reaction occur.
 The above reaction gives  -substituted
naphthalene.
Synthesis of 1-alkyl naphthalene
O
O
+
AlCl3
O
Zn-Hg/HCl
COOH
O
benzene Succinic anhydride
4-oxo-4-phenylbutanic acid
COOH
4-phenylbutanoic acid
1) RMgX
2) HOH
conc. H2SO4
-H2O
O
1-tetralone
HO
R
R
1- Alkyl naphthalene
2- From -benzylidene – propenoic acid
conc. H2SO4
-H2O
OH
O
-Benzylidene-3-propenpoic acid
Zn
-ZnO
naphthalene
O
OH
Chemical Reactions of
naphthalene
1. Reduction
Na
EtOH
1,4- dihydronaphthalene
Na
isoamyl alc.
1,2,3,4-tetrahydronaphthalene
Naphthalene
Tetralene
H2
Ni
decahydronaphthalene
Decalene
2. Oxidation
O
CrO3
AcOH
O
1,4- naphthoquinone
CHO
1) O3
2) H2O/Zn
CHO
Naphthalene
Phthaldehyde
O
O2
V2O3
O
O
Phthalic anhydride
COOH
KMnO4
H
COOH
Phthalic acid
3. Addition of Cl2
Cl
Cl2
Cl
1,4- dichloro- 1,4- dihydronaphthalene
Naphthalene
Cl
excess
Cl
Cl2
Cl
Cl
1,2,3,4- tetrachloro- 1,2,3,4-tetrahydronaphthalene
4. Electrophilic substitution reaction
Q:
Naphthalene udergoes
electrophilic substitution at
position 1 not 2. Explain
At position 1; carbocation intermediate stabilize by two resonance
E
E
E
1
Naphthalene
E
E
Naphthalene
one resonance structure
So carbocation is more stable position 1 than 2
Examples of electrophilic
substitution
NO2
conc. HNO3
conc. H2SO4
1- nitronaphthalene
SO3H
Cl2
conc. H2SO4
40°C
naphthalene-1- sulfonic acid
SO3H
conc. H2SO4
180°C
naphthalene-2- sulfonic acid
Cl
Naphthalene
Cl2
FeCl3
1- chloronaphthalene
COCH3
CH3COCl
AlCl3
CS2
1- Acetylnaphthalene
COCH3
CH3COCl
AlCl3
PhNO2
2- Acetylnaphthalene
Substituted naphthalene
 Activating groups direct the electrophile
to the same ring, while deactivating
groups direct it to the other ring.
Elctrodonating group
(EDG):
NH2, OH, OR, alkyl
Electrowithdrawing group
(EWG):
NO2, CO, COOH, CN, SO3H
Homonuclear attack
Minor
EDG
E
E
EDG
E
Major
Heteronuclear attack
E
E
EWG
EWG
E
Major
E
Major
Examples:
OH
OH
OH
NO2
conc. HNO3
+
conc. H2SO4
NO2
OH
NO2
Major
OH
conc. HNO3
conc. H2SO4
NO2
NO2
conc. HNO3
NO2
NO2
+
conc. H2SO4
NO2
Minor
Major
NO2
NO2
conc. HNO3
+
conc. H2SO4
O2N
NO2
NO2
Naphthalene derivatives
1. Nitronaphthalene
 1. naphthalene is prepared by direct nitration
NO2
conc. HNO3
conc. H2SO4
1- nitronaphthalene
Naphthalene
2. naphthalene is prepared by indirect method
N=N
NH2
NaNO2
HBF4
2- Aminonaphthalene
BF4
CuNO2

-N2
NO2
2. Naphthols
 Preparation:
OH
SO3H
conc. H2SO4
40°C
NaOH
300°C
Naphthalene-1- sulfonic acid
Naphthalene
conc. H2SO4
180°C
1- Naphthol
OH
SO3H
NaOH
300°C
Naphthalene-2- sulfonic acid
2- Naphthol
 Properties:
1- Reaction of  and - naphthols with aryl diazonium salt
OH
O
H
N
Ph
O
N
H
N
Ph
N
Ph-N=N-Cl
NaOH
2- phenylazo-1- Naphthol
Azo form
Ph
Ph
N
N
N
OH
hydrazo form stable by intermol. H.B
H
O
Ph-N=N-Cl
NaOH
2- phenylazo-2- Naphthol
N
H
O
2- Reaction of  and - naphthols with nitrous acid
OH
OH
O
O
H
N
O
N
HONO
1- Naphthol
2- nitroso-1- naphthol
[1,2]naphthoquinone-2-oxime
O
O
N
N
OH
OH
H
O
HONO
2- Naphthol
2- nitroso-2- naphthol
[1,2]naphthoquinone-1-oxime
3- Conversion of  and - naphthols to naphthyl ether
OR
RI
OH
NaOH
OR
1- Naphthol
ROH
conc. H2SO4
RI
OR
NaOH
OH
1- Naphthol
OR
ROH
conc. H2SO4
3. Naphthylamine
 Preparation:
1- Naphthylamine
NO2
NH2
Zn/HCl
conc. HNO3
conc. H2SO4
1- Nitronaphthalene
1- aminonaphthalene
 Preparation:
2- Naphthylamine
Bucherer reaction
OH
NH2
NH3
NH4HSO3
- Naphthol
- naphthylamine
Mechanism
H
OH
OH
O
H
H
SO3NH4
SO3NH4
NH4HSO3
- Naphthol
NH
NH2
NH3
NH2
-NH4HSO3
H
H
SO3NH4
SO3NH4
- naphthylamine
4. Halogenated naphthalene
 A) Preparation of 1- halogented naphthalene
Br
Br2
FeBr3
1- bromonaphthalene
 B) Preparation of 2- halogenated naphthalene via Sandemeyer
NH2
NaNO2
HCl
0°C
2- Naphthylamine
N
Cl
N CuBr
, -N2
Br
Questions:
Convert 2- naphthol to:




A) 2- bromonaphthol
b) Naphthalene -2- carboxylic acid
C) 1,2- naphthaquinone-1- oxime
D) Ethyl –naphthyl ether
5. Alkyl naphthalene
 Synthesis of 1- alkyl naphthalene
O
O
+
Benzene
O
O
Succinic anhydride
Zn-Hg/ HCl
COOH
AlCl3
4- oxo-4-phenylbutanoic acid
COOH
4-phenylbutanoic acid
 Synthesis of 2- alkyl naphthalene
O
O
+
Zn-Hg/HCl
AlCl3
O
H3C
H3C
Toluene
O
Succinic anhydride
HO
O
Zn-Hg/HCl
conc. H2SO4
-H2O
H3C
H3C
HO
O
O
H3C
Se

H3C
2- methyl naphthalene
6. Naphthaquinones
 There are six possible naphthaquinones, but only common are
1,2; 1,4; 2,6- naphthaquinones
O
O
O
O
1,2- Naphthaquinone
O
1,4- Naphthaquinone
O
2,6- Naphthaquinone
Preparation of
naphthaquinones
1,4- Naphthaquinone:
O
CrO3
AcOH
O
Naphthalene
1,4- Naphthaquinone
1,2- Naphthaquinone:
NH2
O
OH
O
K2Cr2O7
H2SO4 or PbO2
1- Amino- 2-naphthol
1,2- Naphthaquinone
2,6- Naphthaquinone:
OH
O
PbO2
benzene
HO
2,6- dihydroxynaphthalenel
O
2,6- Naphthaquinone
7. Naphthoic acid
COOH
1- Naphthoic acid
or
- Naphthoic acid
COOH
2- Naphthoic acid
or
- Naphthoic acid
Preparation of 1-naphthoic
acid
From bromonaphthalene
Br
Mg
dry ether
1- bromonaphthalene
COOH
MgBr
1) CO2
2) H
1- naphthyl magnesium bromide
1- Naphthoic acid
From 1- naphthylamine
Cl
NH2
N
NaNO2
N
CN
CuCN
HCl
1- Naphthylamine
COOH
H2O
H
1- Naphthoic acid
1- naphthonitrile
From 1- acetylacetophenone
COOH
COCH3
I2/NaOH
1- Acetylacetophenone
1- Naphthoic acid
2- Naphthoic acid can be prepared by the same above methods
Anthracene
1
9
8
2
7
3
6
4
10
5
 Anthracene has 4 isomers:
I
II
Resonance I, II are more stable, contain 2 benzene rings.
Synthesis of anthracene
 1. Friedl Crafts
CH2Cl
AlCl3
+
ClH2C
Benzyl chloride
-2H
Anthracene
 2. Elbe reaction
O
Pyrolysis
CH3
o- Methyl- benzenophenone
or o- Benzoyl- toluene
Anthracene
 3. From 1,4- Naphthoquinone
O
O
+
O
1,4- Naphthaquinone
1,3- Butadiene
O
O
CrO3
AcOH
Zn
O
9,10- anthraquinone
Anthracene
The above method shows presence of naphthalene in anthracene
 4. From benzene and phthalic anhydride
O
+
O
O
AlCl3
HOOC
O
Phthalic anhydride
O
H2SO4
Zn
-H2O
O
anthraquinone
Anthracene
Chemical reactions
 1) Diels Alder
O
+
Anthracene
O
O
Maleic anhydride
O

O
O
Endo- anthracene- maleic anhydride adduct
 2) Addition of one molecule of O2
+
Anthracene
O2
O
O
Anthracene epoxide
 3) Halogenation of anthracene
X
X
X2
-HX
X= Cl or Br
Anthracene
X
 4) Oxidation of anthracene
O
Dil HNO3
O
Anthracene
9, 10- Anthraquinone
In using dil. HNO3 only to obtain 9,10- anthraquinone
 4) Reduction of anthracene
Na
isopropanol
Anthracene
9, 10- Dihydroanthracene
Anthraquinone
O
O
Preparation
O
Dil HNO3
K2Cr2O7
O
Anthracene
9, 10- Anthraquinone
O
+
O
O
AlCl3
HOOC
O
Phthalic anhydride
O
H2SO4
-H2O
O
anthraquinone
Chemical Reactions
Zn/ 
Distillation
or
Zn/H/150°C
Anthracene
O
O
Sn/HCl/AcOH
O
9- Anthrone
OH
Zn/ NaOH
OH
Anthraquinol
 Nitration
O
O
O
NO2
O
HNO3
HNO3
H2SO4
H2SO4
O
1- nitro-9,10- anthraquinone
Major NO2
NO2
O
1,5- dinitroanthraquinone
+
NO2
O
NO2
O
1,8- dinitroanthraquinone
 Sulphonation
O
O
O
SO3H
SO3H
Oleum
+
160°C
O
O
O
Anthraquinone-2-sulfonic acid
small
Major
Anthraquinone does not undergo Friedl Craft reaction
•Preparation of 2-amino-anthraquinone
O
O
NH2
SO3H
NH3

O
Anthraquinone-2-sulfonic acid
O
2- amino-anthraquinone
Alizarin
O
OH
OH
O
1,2-dihydroxyanthraquinone
Alizarine
Preparation
O
O
SO3H
Oleum, H2SO4
160°C
O
Anthraquinone
O
9,10- anthraquinone-2- sulfonic acid
1)NaOH, 
2) [O]
O
OH
OH
O
Alizarine
Preparation of Alizarine Blue
O
OH
O
OH
OH
OH
1) conc. HNO3
conc. H2SO4
2) [H]
NH2
O
Alizarine
O
O
OH
OH
1) Glycerol/ H2SO4
2) PhNO2
N
O
Alizarine Blue
Alizarine blue is used for dyeing wool by blue color
Phenanthrene
6
5
1
10
9
4
2
1
10
8
6
14
3
7
2
13
9
5
11
7
8
3
12
14
13
4
11
12
Position of double bond
The most stable
3 benzenoid rings
Preparation of phenanthrene
 1) Howrth method
O
O
COOH
+
Naphthalene
O
AlCl3
Zn-Hg/HCl
O
Succinic anhydride
COOH
conc.H2SO4
O Zn-Hg/HCl
Preparation of 1- alkyl phenanthrene:
R
O 1) RMgX
OH
R
Se
2) HOH
 Preparation of 2- alkyl phenanthrene:
O
R
O
COOH
R
+
Zn-Hg/HCl
AlCl3
O
O
Naphthalene
R
R
COOH
O Zn-Hg/HCl
conc.H2SO4
R
Se
R
 2) Posher synthesis
COOH
CH2COONa
CHO
NO2
+
Ac2O
Zn-Hg/HCl
NO2
COOH
COOH
NaNO2/H2SO4
NH2
N2HSO4
Cu
Phenanthrene
Chemical Reactions
Na/EtOH
9,10-dihydro-phenanthrene
1) O2
2) H2O
CHO
CHO
Biphenyl-2,2'-dicarbaldehyde
Br2
Br
Br
9,10-dibromo-9,10-dihydro-phenanthrene
Br
Br2
FeBr3
9-bromo-9,10-dihydro-phenanthrene
H2O2
AcOH
COOH
COOH
Diphenic acid
Benzil-Benzilic rearrangement
COONa
Ph C O
NaOH
Ph C O
Ph
C
OH
Ph
Benzilic acid salt
Benzil
Mechanism
OH
Ph C O
Ph C O
HO
OH
Ph C O
C O
Ph C O
Ph C O
Ph
O
Proton
transfer
C O
Ph C OH
Ph
COOH
O
NaOH
OH
H
O
9-hydroxy-9H-flourene-9-carboxylic acid
Phenanthraquinone
Mechanism
O
OH
HO
COOH
O
O
O
O
COO
Proton
transfer
OH
Phenanthraquinone
 Preparation
O
K2Cr2O7
H2SO4
O
Phenanthrene
Phenanthraquinone
Condition necessary for
aromaticity
Any compound to be aromatic, it must be;
 1. Cyclic
 2. Planner
 3. All atoms must be SP2
 4. All double bonds must be conjugated
 5. Obey Huckle rule which state that any
aromatic compound must contain 4n+2 pi
electrons where n 0,1,2,3,…
Examples
n=1
 electron
n=2
 electron
n=3
 electron
Examples of non- benzenoid
aromatic cmpound
All are aromatic( cyclic, planner,1, and agree
with Huckle rule: 4n+2= 6 (n=1)
Examples of non- aromatic
Not aromatic; both contain Sp3
Not aromatic
Not aromatic
Aromatic; cyclic, planner,
Does not obey Huckel rule
Does not obey Huckel rule
obey Huckel rule
4n+2=8; n=1.5
4n+2=4; n=0.5
4n+2=2; n=0
Aromatic
Not Aromatic
Aromatic
4n+2=10; n=2
8 pi electrons
4n+2=14; n=3
Aromatic
Aromatic
4n+2=10; n=2
4n+2=10; n=2