PHENOL INTRODUCTION, REACTIVITY, ACIDITY, FACTOR AFFECTING ON ACIDITY, PREPARATION, REACTION,COMPARISON OF ACIDITY WITH ALCOHOL AND ACID, USES OF PHENOL, CRESOL, RESORCINOL, NAPTHOL

1. PHENOLS
MOTE G.D.
ADCBP,ASHTA

2. PHENOLS
Aromatic compounds containing one or more OH
groups directly attached with carbon of benzene ring
are called Phenols.
Simplest phenol is Carbolic Acid C6H5OH
Term Phenol is derived from an old name of benzene
– Phene
Phenyl : C6H5

3. NOMENCLATURE OF PHENOLS
In IUPAC –OH group is represented as hydroxyl. It is used asa
prefix, while benzene part of the molecule is used as suffix.
1,2- dihydorxybenzene
O-hydroxyl phenol
(Catechol)
Phenol 1,3- dihydorxybenzene
m-hydroxyl phenol
(Resorcinol)
1,4- dihydorxybenzene
p-hydroxyl phenol
(Hydroquinone)

4. NOMENCLATURE
2-nitrophenol
O-nitrophenol
3-nitrophenol
m-nitrophenol
4-nitrophenol
p-nitrophenol
2,4,6-trinitrophenol
Picric Acid

5. STRUCTUREOFPHENOLS
The alcohol functional group consists of O atom bonded to
sp2 hybridized aromatic Catom and H atom via σbond
Both C-O and O-H bonds are polar
Conjugation exist between an unshared electron pair of the O
and Benzene Ring
This results in, as compared to
alcohols:
A shorter C-O bond
A more basic OH group
A more acidic OH proton

6. Intramolecular hydrogen bonding is possible in some ortho-substituted phenols. This intramolecular
hydrogen bonding reduces water solubility and increases volatility. Thus, o-nitrophenol is steam
distillable while the isomeric p-nitrophenol is not.
N
O
H
O
O
o-nitrophenol
bp 100oC at 100 mm
0.2 g / 100 mL water
volatile with steam
OH
NO2
p-nitrophenol
bp decomposes
1.69 g / 100 mL water
non-volatile with steam

7. PHYSICALPROPERTIESOF PHENOLS
Colorless, crystalline, poisonous solid with phenolic
odor
Melting point 41oC and Boiling Point 182oC
Sparingly soluble in water forming pink solution at
room temperature
Completely soluble above 68.5oC
Causes blisters on skin
Used as disinfectants and in washrooms

8. ACIDITY OF PHENOLS
Phenols are more acidic (pKa ≈ 10) than alcohol (pKa ≈ 16-20)
Phenols are less acidic than Carboxylic acids (pKa ≈ 5)
COMPARISON OFACIDITY OF PHENOLS AND ALCOHOLS
Phenol exists asresonance hybrid of followingstructures

9. Due to resonance O atom acquires a positive charge and hence attracts
electron pair of O-H bond leading to the release of H+
Carbon atom of C-OH group of phenol (sp2 hybridized) is more electrophilic than
Carbon atom in Alcohols (sp3 hybridized)
In phenols, a greater inductive effect facilitated release of
proton
Thus phenols are more acidic than alcohols because resonance is impossible inalcohols
Phenoxide is more resonance stabilized than phenol but in case of alcohol,
alkoxide is not stable because there is no possibility for the delocalization.

10. COMPARISON OF ACIDITY OF PHENOLS ANDCARBOXYLIC ACIDS
Resonating structures of carboxylicacids:
Carboxylic acids ionize as:R-COOH  R-COO- + H+
The carboxylate anion exhibits following resonating
structures:
The resonating structures of RCOOH (Iand II)are not equivalent and hence less
stable
The resonating structures of RCOO- ion (IIIand IV)are equivalent and hence
more stable
Thus RCOOH have tendency to undergo ionization and form morestable
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11. The resonating structures of phenoxide ion are not equivalent asshown
below:
The resonating structures of RCOO-ion are equivalent. Hence RCOO-ion is
relatively more resonance stabilized that Phenoxide ion.
Thus a carboxylic acid is more acidic than a phenol.
RELATIVEACIDITY ORDER OF SOME COMMON COMPOUNDS:
RCOOH > H2CO3 > C6H5OH > H2O > ROH

12. EFFECT OF SUBSTITUENTS ON THE ACIDITY OFPHENOLS
Electron attracting substituents tend to disperse negative charge of the
phenoxide ion thus stabilize the ion and increase the acidity of phenols.
Electron releasing substituents tend to intensify the charge, destabilize the
ion, diminish the resonance and decrease the acidity.

13. PREPARATIONOF PHENOL
REACTION OF SODIUM SALT OF BENZENE SULFONIC ACID
WITH NaOH:
Sodium benzene sulfonate on fusion with strong alkali like NaOH at
300oC give sodium phenoxide which on treatment with HCl gives
phenol

14. PREPARATIONOF PHENOL
BASEHYDROLYSIS OF CHLOROBENZEN (DOW’S
METHOD)
Chlorobenzene is hydrolysed by heating with 10% NaOH at 360oC
under high pressure to form sodium phenoxide which on treating
with HCl gives phenol

15. PREPARATIONOF PHENOL
ACIDIC OXIDATION OF CUMENE
It is recently developed commercial method for preparation of phenol.
Cumene is oxidized by atmospheric oxygen is presence of metal catalyst
into Cumene Hydroperoxide.
The hydroperoxide is converted into phenol through acid catalyzed
arrangement

16. PREPARATIONOF PHENOL
Preparation of phenol from Aryl Diazonium salts
Aryl diazonium salts are prepared by reaction of aryl amines
with nitrous acid
Aryl diazonium salts can be converted into phenols
using
H2O/H2SO4/ heat

17. REACTIVITYAND REACTIONSOFPHENOLS
Phenols are very reactive towards electrophilic aromatic substitution.
OH group is strongly activating ortho-/para- directing group.
ELECTROPHILICAROMATIC SUBSTITUTION

18. Strong activation means milder reaction conditions than those used for
benzene.
Phenols are so activated that poly-substitution can be a problem.
OXIDATION OF PHENOLS
Phenols are very reactive towards oxidizing agent.
The oxidation takes place through several steps eventually destroying the
ring.
Reaction Benzene Phenol
Nitration Conc. HNO3 / H2SO4 Dil. HNO3 in H2O or CH3COOH
Sulfonation H2SO4or SO3/H2SO4 Conc. H2SO4
Halogenation X2/Fe or FeX3 X2
Alkylation RCl/AlCl3 ROH/H+ or RCl/AlCl3
Acylation RCOCl/AlCl3 RCOCl/AlCl3
Nitrosation - Aq. NaNO2/H+

19. REACTION WITH SODIUM METAL / CARBOXYLATION OF PHENOLS(KOLBE-
SCHMITT REACTION)
“The reaction of sodium salt of phenol with CO2 is called Kolbe Reaction. Itis
carbonation of phenol.”
At low temperature Sodium salicylate (sodium-o-hydroxyl benzoate) is formed,
at higher temperature o-product is isomerizes to p-isomer
CO2 act as electrophilic center in this reaction. Acidification of the salt gives
corresponding hydroxyl acid.

20. Phenols, reactions:
1. as acids( Formation of Salt)
2. ester formation
3. ether formation
4. EAS
a) nitration f) nitrosation
b) sulfonation g) coupling with diaz. salts
c) halogenation h) Kolbe
d) Friedel-Crafts alkylation i) Reimer-Tiemann
e) Friedel-Crafts acylation

21. as acids:
with active metals:
with bases:
CH4 < NH3 < HCCH < ROH < H2O < phenols < H2CO3 < RCOOH < HF
OH
Na
ONa
sodium phenoxide
+ H2(g)
OH
+ NaOH
ONa
+ H2O
SA SB WB WA

22. CH4 < NH3 < HCCH < ROH < H2O < phenols < H2CO3 < RCOOH < HF
OH
+ NaOH
ONa
+ H2O
SA SB WB WA
water insoluble water soluble
OH
+ NaHCO3 NR phenol < H2CO3

23. insoluble soluble insoluble
insoluble soluble soluble
water 5% NaOH 5% NaHCO3
phenols
carboxylic acids
CH4 < NH3 < HCCH < ROH < H2O < phenols < H2CO3 < RCOOH < HF

24. We use the ionization of acids in water to measure acid strength (Ka):
HBase + H2O H3O+ + Base-
Ka = [H3O+ ][ Base ] / [ HBase]
ROH Ka ~ 10-16 - 10-18
ArOH Ka ~ 10-10
Why are phenols more acidic than alcohols?

25. ROH + H2O H3O+ + RO-
ArOH + H2O H3O+ + ArO-
OH OH O O O O O
Resonance stabilization of the phenoxide ion, lowers the PE of the products of
the ionization, decreases the ΔH, shifts the equil farther to the right, makes
phenol more acidic than an alcohol

26. effect of substituent groups on acid strength?
OH
G + H2O
O
G + H3O
Electron withdrawing groups will decrease the negative charge in the phenoxide, lowering the PE,
decreasing the ΔH, shifting the equil farther to the right, stronger acid.
Electron donating groups will increase the negative charge in the phenoxide, increasing the PE, increasing
the ΔH, shifting the equilibrium to the left, weaker acid.

27. Number the following acids in decreasing order of acid strength (let # 1 = most acidic, etc.)
OH OH OH OH OH
NO2 CH3 Br
3 5 1 4 2

28. SO3H COOH OH CH2OH
1 2 3 4

29. 2. ester formation (similar to alcohols)
OH
CH3
+ CH3CH2C
O
OH
H+
CH3CH2C
O
O
H3C
+ H2O
OH
COOH
salicyclic acid
+ (CH3CO)2O
O
COOH
CH3C
O
aspirin

30. O
COOH
CH3C
O
aspirin
analgesic
anti-inflamatory
antipyrretic
anticoagulant
Reye's syndrome
not to be used by children
with high fevers!
OH
NHCH3C
O
acetaminophen
aspirin substitute
Tylenol
Kidney damage!

31. 3. ether formation (Williamson Synthesis)
Ar-O-Na+ + R-X  Ar-O-R + NaX
note: R-X must be 1o or CH3
Because phenols are more acidic than water, it is possible to generate the phenoxide in situ using NaOH.
OH
CH3
+ CH3CH2Br, NaOH
OCH2CH3
CH3

32. 4. Electrophilic Aromatic Substitution
The –OH group is a powerful activating group in EAS and an ortho/para director.
a) nitration
OH OH
NO2
NO2
O2N
polynitration!
OH
dilute HNO3
OH OH
NO2
NO2
+
HNO3

33. OH
Br2 (aq.)
OH
Br
Br
Br no catalyst required
use polar solvent
polyhalogenation!
OH
Br2, CCl4
OH OH
Br
Br
+
non-polar solvent
b) halogenation

34. c) sulfonation
OH
H2SO4, 15-20oC
OH
SO3H
H2SO4, 100oC
OH
SO3H
At low temperature the reaction is non-reversible and the lower Eact ortho-product is formed (rate
control).
At high temperature the reaction is reversible and the more stable para-product is formed (kinetic
control).

35. d) Friedel-Crafts alkylation.
OH
+ H3C C CH3
CH3
Cl
AlCl3
OH
C CH3
CH3
H3C

36. e) Friedel-Crafts acylation
OH
CH3CH2CH2C
O
Cl
+
AlCl3
OH
O
Do not confuse FC acylation with esterification:
OH
CH3CH2CH2C
O
Cl
+ O
O

37. OH
O
OH
CH3CH2CH2C
O
Cl
+ O
O
AlCl3
Fries rearrangement of phenolic esters.

38. f) nitrosation
OH
HONO
OH
NO
EAS with very weak electrophile NO+
OH
CH3 NaNO2, HCl
OH
CH3
NO
p-nitrosophenol

39. g) coupling with diazonium salts
(EAS with the weak electrophile diazonium)
OH
CH3
+
N2 Cl
benzenediazonium
chloride
CH3
OH
N
N
an azo dye

40. h) Kolbe reaction (carbonation)
ONa
+ CO2
125o
C, 4-7 atm.
OH
COONa
sodium salicylate
H+
OH
COOH
salicylic acid
EAS by the weakly
electrophilic CO2
O C O


41. i) Reimer-Tiemann reaction
OH
CHCl3, aq. NaOH
70oC
H+
OH
CHO
salicylaldehyde
The salicylaldehyde can be easily oxidized to salicylic acid

42. Reaction with FeCl3
Phenol gives purple color with one or two drops of ferric chloride due to formation of
complex
OH
FeCl3
O
Fe
3

43. Reaction with Zinc dust
When phenol is distilled with zinc dust to produce benzene
OH
Zn ZnO

44. Gatterman reaction
This involves treatment of phenol with mixture hydrogen cyanide and hydrogen
chloride
OH
HCN/HCl
AlCl3 CH=NH
OH
H2O
CHO
OH
phenol 2-(iminomethyl)phenol 2-hydroxybenzaldehyde

45. Reaction with phthalic anhydride
Phenol reacts with phthalic anhydride in the presence of sulfuric acid to form
phenolphthalein
OH
phenol
C
C
O
O
O
C
C
O
O
OH
HO
phthalic anhydride
phenolphthaliein

46. Reaction with Formaldehyde
Phenol treated with alkaline solution of formaldehyde to form o and p-hydroxy benzyl
alcohol
OH
phenol
H C
O
H
NaOH
OH
CH2OH
OH
CH2OH

47. Oxidation
Phenol undergoes oxidation with air or chromic acid to form p-benzoquinione
OH
phenol
CrO3
O
O

48. Catalytic hydrogenation
Phenol passed over nickel catalyst to form cyclohexanol
OH
phenol
Ni
160°C
3H2
OH

49. USES OF PHENOL
1. Medical uses
Phenol sprays are mostly used in medical industry. Phenol sprays work very well in
the painful and irritating areas. They have anesthetic and analgesic combinations
which help in getting instant relief from allergy also. Sore throat got immediate relief if
phenol is used. It is also used in manufacturing if pesticides and insecticides in the
pharma industry.
2.Plastic manufacturing industry
Two third of total phenol is used in preparing reagents. Reagents are used in plastic
manufacturing industries. When phenol is condensed then it produces bisphenol with
acetone.
3.Paint industry
Phenol is also used to produce epoxy resins for paints coatings and moldings. It is
also used in polycarbonate plastics which can be seen in CDs and domestic electrical
appliances.
4. Cosmetic Industry
Phenol is also used in cosmetic industry in the manufacturing of sunscreens, skin
lightening creams and hair coloring solutions. It is an ingredient that is used to kill
microorganisms. It also prevents or inhibits the growth and reproduction of
microorganisms.
5.Extraction Industry
Extraction industry uses phenol in the study and extraction of bio-molecules. There is
various application of phenol find by molecular biology in the extraction of nucleic
acids from tissue samples for further investigations.

50. USES OF CRESOL
Cresols are precursors or synthetic intermediates to other
compounds and materials, including plastics, pesticides,
pharmaceuticals, and dyes.
Derivatives of p-cresol include:
1.Bupranolol, a non-selective beta blocker
2.Butylated hydroxytoluene, a common antioxidant
3.Indo-1, a popular calcium indicator
Derivatives of m-cresol include:
Amylmetacresol, an antiseptic
Bevantolol, (RS)-[2-(3,4-dimethoxyphenyl)ethyl][2-hydroxy-3-(3-
methylphenoxy)propyl]amine
Bromocresol green
Chloro-m-cresol which is used as a household disinfectant
Tolimidone, 5-(3-methylphenoxy)pyrimidin-2(1H)-one

51. USES OF RESORCINOL
1.Used externally, it is an antiseptic and disinfectant, and is used 5 to 10% in
ointments in the treatment of chronic skin diseases such
as psoriasis, hidradenitis suppurativa, and eczema of a sub-acute.
2.A 2% solution used as a spray has been used with marked effect in hay
fever and in whooping cough.
3. It can be included as an anti-dandruff agent in shampoo or
in sunscreen cosmetics
4. It has also been employed in the treatment of gastric ulcers in doses of
125 to 250 mg in pills, and is said to be analgesic and haemostatic in its
action.
5. In large doses, it is a poison,
causing giddiness, deafness, salivation, sweating, and convulsions. It is also
worked up in certain medicated soaps.
6. It is also worked up in certain medicated soaps

52. USES OF NAPTHOL
1. 1-Naphthol is a precursor to a variety of insecticides
including carbaryl and pharmaceuticals including nadolol. It
undergoes azo coupling to give various azo dyes,
2. In Molisch's test, 1-naphthol dissolved in ethanol, known as
Molisch's reagent, is used as reagent for detecting the
presence of carbohydrates. The test known as Molisch's test
would give a red- or purple-colored compound to indicate the
presence of carbohydrate.
3. The Sakaguchi test uses 1-naphthol with sodium
hypobromite to detect the presence of arginine in proteins.
4. The Voges–Proskauer test uses 1-naphthol in potassium
hydroxide (KOH) solution to detect the breakdown
of glucose into acetoin which is used by bacteria for external
energy storage. A positive test will be indicated by the
appearance of a red color of the original yellow solution.

53. DIFFERENCEBETWEENALCOHOLS AND PHENOLS
ALCOHOL
OH group is attached to an alkyl group
Hydroxyl derivatives of alkane
The compounds in which one hydrogen of
water is replaced by an alkyl group
General formula ROH
Lower alcohols are colorless liquids
They characteristics sweet smell and
burning taste
pKa ≈ 16 - 20
Readily soluble in water but solubility
PHENOL
OH group is attached to an aryl group
Hydroxyl derivatives of benzene
The compounds in which one hydrogen of
water is replaced by an aryl group
General formula C6H5OH
Colorless crystalline deliquescent solids (M.P
41oC)
They have a characteristics phenolic odor
pKa ≈ 10
Sparingly soluble in water forming a pink
osolution but completely soluble above 68.5 C
Phenolate ions have resonance structures but
alcohols do not have resonance structures
decreases in higher alcohols

54. The End