Organic chemistry

1. By
Rashmi Mishra

2. INTRODUCTION
• Compound with the general formula ArOH (Phenyl, substituted phenyl or some other aryl
group)
OH
Cl
OH
CH3
OH
OH
COOH
OH
OH
OH
OH
OH
OH
OH
Phenol O - Chlorophenol m - Cresol
p - Hydroxy benzoic acid
Catechol Resorcinol
Hydroquinone
2 - Naaphthol

3. CHEMICAL REACTIONS OF PHENOL
1. Acidity salt formation
2. Ester formation
3. Ring substitution reactions
a. Nitration
b. Halogenation
c. Sulfonation
d. Friedal craft alkylation
e. Friedal craft acylation
f. Nitrosation
g. Coupling with diazonium salt
h. Carbonation
i. Reimer-Tiemann reaction
j. Williamson synthesis

4. 1. Acidity salt formation
Phenol Salt Phenol
Aq. Mineral acids
COOH/Carbonic acid
Aq. OH
Ar - OH+ OH
-
ArO
-
+ H2O
strong acid Weaker acid
ArO
-
+ H2CO3 Ar - OH+ HCO 3
-
strong acid Weaker acid
COOH > Phenol > H2O (Ka of COOH = 10-5) (Ka of Phenol 10-10 )
COOH > Phenol > Alcohol (Ka of Alcohol = 10-16 to 10-18 )

5. Why OH attached to Aromatic ring is more acidic than OH attached to R??????
R - O : H
. .
. .
Dissociation
Ionization
H
+
+ R - O :
-
. .
. .
Alkoxide ion
(Represented by single structure)
. .
O : H
:
. .
O : H
:
I II
Phenol
H
+
+
. .
O :
-
:
. .
O :
-
:
III IV
Phenoxide ion
- contain benzene ring --- so exist in hybrid of kekule I, II, III
and IV----- due to resonance stabilizes both molecule and
ions...... so does not differ in energy content.
- we can expect acidity of phenol and alcohol same if no longer
factor involve.

6. Additional structures as oxygen is basic ------ can share more than a pair of electron
with ring.
. .
V
H
O : H
:
-
+
. .
VI
:
-
+
H
O : H
. .
VII
:
-
+
H
O : H
- Carry both +ve and -ve charges.
- Energy nned to be supply to separate +ve and
-ve charge.
- Less stable than phenoxide ion.
. .
VIII
H
O :
:
-
. .
IX
:
-
H
O :
. .
X
:
-
H
O :
- Carry only -ve charge.
- Net effect of resonance is to stabilize phenoxide
ion to greater extend than phenol.
- Thus make Ka larger than alcohol.

7. EFFECT OF SUBSTITUENT ON ACIDITY OF PHENOL
1. Nature of substituent:
a. Electron withdrawing substituent (-NO2 , -CN, -X):
Withdraws electron Disperse –ve charge Stabilizes compound Increase acidity
b. Electron releasing substituent (-OH, -R):
Releases electron Destabilize phenoxide ion Increse –ve charge Decreaes acidity of phenol
2. Position of substituent:
Electron withdrawing and electron releasing group more pronounce at ortho and para
(Due to resonance)

8. . .
I
NO2
O :
-
:
. .
II
NO2
O :
-
:
-
III
NO2
O :
-
:
-
. .
IV
:
-
. . . .
O
O
N
O :
-
V
:
-
O
O
N
O :
-
. .
VI
:
. .
VII
:
-
VIII
:
-
. .
IX
. . . .
X
Ortho nitro phenoxide ion
Para nitro phenoxide ion
NO2
O :
-
NO2
O :
-
NO2
O :
-
NO2
O :
-
:
-
O
O
N
O :
-
:
-
-In ortho and para
conjugation extended upto
oxygen atom of NO2 not in
meta isomer.
- Greater resonance
stabilization occurs in ortho
and para position
so ortho and para nitro
phenol > acidic than meta
nitro phenol.
para nitro phenol > ortho
nitro phenol > meta nitro
phenol.
Meta nitro phenoxide ion
:
. .
XII
:
-
XIII
:
-
. .
XIV
. . . .
NO2
O :
-
NO2
O :
-
NO2
O :
-
NO2
O :
-
. .
:
-
XI

9. Why para nitro phenol > acidic than ortho nitro phenol ??????
O
O
N
O
H
- Intermolecular H bnding
can occur between oxygen of
nitro group and OH of phenol
in ortho nitro phenol.
- Not possible in para nitro
phenol.

10. 2. Ester formation
Ar - OH
RCO - OAr + HCl
RCOCl
ArSO2Cl ArSO2 - OAr + HCl
OH
+
COCl
NaOH
O
C
O
Phenol Benzoyl
Chloride
Phenyl Benzoate
+
P - Nitro phenol
O2N OH
O
O
C
H3 C
O
C
C
H3
CH3COONa
CH3
O
C
O2N O
Acetic anhydride
P - Nitro phenol acetate
General
Reaction
Example

11. 3. Ring Substitution
a. Nitration
OH
Dil. HNO3
20 o
C
NO2
OH
+
NO2
OH
Phenol O - Nitro Phenol
P - Nitro Phenol
Isomeric products
(Separated by distillation)
OH
Phenol
2,4,6 - Trinitro Phenol
If Conc. HNO3 is used:
Con. HNO3
O2N
NO2
NO2
OH

12. 3. Ring Substitution
b. Halogenation
OH
Phenol
2,4,6 - Tribromo Phenol
Br
Br
Br
OH
Br2, H2O Treatment of phenol with aq.
solution of Br ------
replacement of every
hydrogen on ortho and para
position to OH group.
OH
Phenol O - Bromo Phenol
Br
OH
Br2, CS2
0 o
C
Br
OH
+
P - Bromo Phenol
( Chief Product)
If halogenation is carried out
in solvent of lower polarity
(CHCl3 or CS2 ) ------ reaction
limited to monohalogenation

13. 3. Ring Substitution
c. Sulfonation
OH
O - Phenol sulfonic acid
H2SO4
15 - 20 o
C
SO3H
OH
Phenol
100 o
C
SO3H
OH
+ O
H2
+ O
H2
P - Phenol sulfonic acid

14. d. Friedel Craft Alkylation (Preparation of alkylphenols)
OH OH
CH3
C
H3 CH3
Phenol
+ C
H3 CH3
CH3
Cl
Tert. butyl chloride
HF
P - Tert. butyl chloride

15. e. Friedel Craft Acylation (Fries rearrangement)
OH
Phenol Phenyl propionate
(Esters of phenol)
Phenol
Acid,
Acid chlorides/
Acid anhydrides
Esters
C2H5COCl
(Ethanoyl Chloride)
O
C2H5
C
O
AlCl3
CS2
OH O
C2H5
C
O - Hydroxyphenyl ethyl
ketone
(Volatile in steam)
+
O
H5C2
C
OH
P - Hydroxyphenyl ethyl
ketone
(Non - Volatile in steam)
when esters of phenol is
heated with aluminium
chloride------- acyl group
migrates from phnolic oxygen
to an ortho or para positions
to form Ketone
CH3
OH
O
O
C
H3 C
O
C
C
H3
O
CH3
C
CH3
O
M - Cresol
M - Cresyl acetate
AlCl3
25 o
C
60 o
C
O CH3
C
OH
CH3
1
O
C
H3
C
OH
CH3
1
2 - Methyl - 4 - hydroxy acetophenone
4 - Methyl - 4 - hydroxy acetophenone

16. f. Nitrosation
OH
Phenol
+ NaNO 2 + H 2SO4
NO
OH
Forms Nitrosonium ion
- Nitrosonium ion is weakly
electrophile ----- attacks
strongly activted phenol
Sodiumnitrite
P - Nitrosophenol
80% yield
General Reaction
Example
+ NaNO 2 + H 2SO4
Sodiumnitrite
4 - Nitroso - 2 -methyl phenol
CH3
OH
m - Cresol
CH3
NO
OH

17. g. Coupling with diazonium salt
+
1 - Phenyl naphthyl azo
General Reaction
Ar - OH + Ar - N 2
+
Ar - N = N - Ar
-
+ H
+
Phenol Diazoniumsalt Azo compounds
Alkaline
Aromatic ring should have
powerful electron releasing
group. Ex. -OH, -NR2 , -NHR,
-NH2
Substitution usually occurs at
para to activation group in
mild alkaline condition.
- In aidic mediumphenol will
exist in unionized form -----
Less reactive than phenoxide
ion-------- so lower the rate of
coupling.
Weakly electrophile (capable of
reacting every reactive ring
(Phenoxide ion)
Example
OH
2 - Naphthol
Cl
N
+
N
+ N
OH
N
Diazoniumsalt of benzene

18. g. Carbonation (Kolbe reaction / Synthesis of phenolic acids)
Salt of phenol reacts with CO2 --------- brings about substitution of carboxylic group –COOH
for hydrogen of ring = Kolbe reaction.
ONa
+
O
O
C





 125 o
C,
4-
7 atm
COONa
OH
H+
COOH
OH
Sodium salt
of phenol
Sodium
salicylate
Salicylic acid
Phenol O - hydroxybenzoic acid / P - hydroxybenzoic acid
(More volatile)
(Separate with distillation)

19. i. Reimer – Tiemann reaction ( Aldehyde formation / Synthesis of phenolic
aldehydes)
Treatment of phenol with chloroform and aq. Hydroxide …….. Provide aldehyde group onto
ring (at ortho to OH ) = Reimer- Tiemann reaction.
OH
CHCl3, 70 o
C
aq. NaOH
CHCl 2
O
CHO
O
HCl
CHO
OH
Phenol Benzal
chloride
Salicyl
aldehyde
Mechanism
OH
-
+ CHCl 3 H2O + :CCl 3 Cl
-
+ :CCl 2
Chloroform
Dichlorocarbene
(Electrophilic
reagent)
Step I
Step II
O
-
+ :CCl 2
CCl 2
-
H
O
CHCl 2
OH

20. 4. Williamson synthesis (Ether formation): Nucleophilic substitution reaction
Phenol
Alkaline solution
Alkyl halides
Alkyl / aryl ether
ArO
-
+ RX Ar - O - R + X
-
Phenoxide
ion
Alkyl
halide
Ether
Example
OH C2H5I
+
aq. NaOH

OC2H5
Phenol
Ethyl
Iodide Ethyl phenyl ether
OH CH3 - O - SO 2 - O - CH 3
+
aq. NaOH

CH3
Phenol
Methyl
sulfate Anisol
(Methyl phenyl ether)
+ CH3OSO 3
-
Na
+
In alkaline mediun
Phenol exist in
phenoxide ion

21. Example
ONa
+
Phenol
Br +
CH3CH2CH2Br
CH3CH2CH2O
-
Na
+
O
H2CH2CH3C
Phenyl - n - propyl ether
Propyl bromide
Phenyl bromide
Sodium
propoxide
Feasible
Due to low reactivity
arylhalide cannot be
used