Chemistry Topic

1. 10/18/2020
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Alcohols and Phenols
Dr. Satish Dhirendra Mitragotri
(M.Sc., Ph.D., SET, NET, GATE and M.B.A. (Finance))
Department of Chemistry
Walchand College of Arts and Science, Solapur
Alcohols and Phenols - Introduction
•Compounds with –OH group attached to carbon
of alkyl group are known as alcohols
•CH3-OH, CH3-CH2OH
• Compounds with –OH group attached to carbon
of aryl group are known as Phenols
•C6H5-OH, CH3-C6H4-OH
•These are important class of compounds as they
find applications in every day life.
•Alcohols – Disinfectants, sanitizers, solvents,
cream bases, soaps, cosmetics
• Phenols – Soaps, Disinfectants, polymers etc.
Alcohols and Phenols - Classification
•Classification of alcohols
•Classification based on position of –OH group in
alkyl chain.
•Primary alcohols – In primary alcohols –OH
group is attached to primary carbon (carbon
attached to one more carbon atom). e.g.
•Ethyl alcohol:CH3CH2-OH,
•Propyl alcohol CH3CH2-CH2-OH
•Butyl alcohol CH3CH2-CH2-CH2-OH
Alcohols and Phenols - Classification
•Secondary alcohols In secondary alcohols –OH
group is attached to secondary carbon (Carbon
attached to two more carbon atoms). e.g.
•2-propanol
•2-Butanol
•2-Phenyl ethanol
CH CH3
OH
CH3
CH CH3
OH
CH3
CH2
OH
CH3
2-Propanol 2-Butanol
2-Phenyl ethanol
•Tertiary alcohols - In tertiary alcohols –OH group
is attached to tertiary carbon (Carbon attached to
three more carbon atoms). e.g.
Alcohols and Phenols - Classification
C CH3
OH
CH3
CH3
CH3
OH
CH3
CH2
OH
CH3
C
CH3
CH3
2,2-dimethyl
2-Propanol
2-methyl
2-Butanol 2-Phenyl,2-propanol
Alcohols and Phenols - Classification
•Classification of alcohols
•Classification based on number of –OH group in
given molecule.
•Monohydric alcohols – In monohydric alcohols
only one –OH group is present. e.g.
•Ethyl alcohol:CH3CH2-OH, Propyl alcohol CH3CH2-
CH2-OH, Butyl alcohol CH3CH2-CH2-CH2-OH
CH2
CH3
OH
CH2
CH3
OH
CH2
CH3
CH3
OH
CH
Ethanol 1-propanol 2-propanol

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Alcohols and Phenols - Classification
•Dihydric alcohols – In dihydric alcohols two –OH
groups are present. e.g.
Trihydric alcohols – In Trihydric alcohols three
–OH groups are present. e.g.
CH2
CH2
OH OH
CH2
CH
OH OH
CH3
Ethan 1,2-diol Propane 1,2-diol
CH2
CH
OH OH
CH2
OH
Glycerol
Alcohols and Phenols - Classification
•Polyhydric alcohols – In Polyhydric alcohols more
than three –OH groups are present. e.g. Glucose
Alcohols and Phenols - Nomenclature
Sr.
No.
Formula Common
name
IUPAC Name
1 Ethyl alcohol Ethanol
2 Isopropanol 2-propanol
3 Tertiary
butanol
2-methyl, 2-
propanol
CH2
CH3
OH
CH CH3
OH
CH3
C CH3
OH
CH3
CH3
Alcohols and Phenols - Nomenclature
Sr.
No.
Formula Common
name
IUPAC Name
4 Ethylene
glycol
Ethane 1,2-diol
5 Propylene
glycol
Propane 1,2-
diol
6 Glycerol Propane 1,2,3-
triol
CH2
CH2
OH OH
CH2
CH
OH OH
CH3
CH2
CH
OH OH
CH2
OH
Alcohols –Methods of synthesis
•Synthesis of ethylene glycol
1. From ethylene (CH2=CH2)
a) Hydroxylation of ethylene – Ethylene is gas
when it is passed through the cold solution of
alkaline potassium permanaganate it produces
ethylene glycol.
CH2
CH2
OH OH
KMnO4
, H2
O
CH2
CH2
Hydroxylation
Ethylene glycol
Alcohols –Methods of synthesis
•Synthesis of ethylene glycol
1. From ethylene (CH2=CH2)
b)By reaction of ethylene with hypochlorous acid
– Ethylene when reacted with hypochlorous acid
(HOCl) it gives 2-chloro ethanol which on further
treatment with aqueous Na2CO3 (or by action of
aqueous calcium hydroxide)produces ethylene
glycol.
CH2
CH2
HOCl CH2
CH2
OH Cl
NaHCO3, H2O
NaOH
CH2
CH2
OH OH
Ethylene glycol
2-chloro ethanol

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Alcohols –Methods of synthesis
•Synthesis of ethylene glycol
2.From ethylene dibromide (Br-CH2-CH2-Br)
ethylene dibromide on treatment with aqueous
sodium carbonate gives ethylene glycol.
3.From ethylene oxide- Ethylene oxide on ring
opening with dilute acids gives ethylene glycol.
Na2CO3, H2O CH2
CH2
OH OH
CH2
CH2
Br Br
CO2
2 NaBr
+ +
Ethylene glycol
CH2
CH2
OH OH
CH2
CH2
O
/ H2
O, Hydrolysis
Ethylene glycol
H+
Alcohols –Chemical reactions
•Ethylene glycol is colorless viscous liquid with
B.P. at 470K, it is toxic in nature, soluble in water
and other alcohols.
1.Weak acidic nature of –OH group (Reaction with
Na) – When reacted with sodium metal it librates
hydrogen gas with formation of monosodium
derivative. If excess of sodium metal is used it
forms disodium glycolate.
CH2
CH2
OH OH
CH2
CH2
OH O
CH2
CH2
O
O
Na, 323 K
Na+
Na, 433 K
Monosodium glycolate
Na+
Na+
Disodium glycolate
+ H2
Ethylene glycol
Alcohols –Chemical reactions
2. Reaction with HCl– When reacted with
hydrochloric acid it first forms ethylene
chlorohydrine (2-chloro propanol) when reaction
is contunied at higher temperature in excess of
HCl it gives dichloroethane.
3. Oxidation reactions of ethylene – Ethylene has
C=C which can be attacked by oxidizing reagents
to yield variety of products.
CH2
CH2
OH OH - H2O
CH2
CH2
OH Cl
CH2
CH2
Cl
Cl
- H2O
HCl, 433 K
Ethylene glycol 2-chloro ethanol 1,2-dichloro ethane
HCl, 473 K
Alcohols –Chemical reactions
3a)Periodic acid oxidation – Ethylene glycol on
oxidation with periodic acid (HIO4) gives two
moles of formaldehyde. This reaction is used to
determine number of CH2-OH groups present in
given molecule. One -CH2-OH gives one molecule
of formaldehyde.
CH2
CH2
OH OH
HIO4
- HIO3, - H2O
Ethylene glycol
Periodic acid
H C
O
H
Methanal
Formaldehyde
Alcohols –Chemical reactions
3b) Lead tetra acetate ( Pb(OCOCH3)4) oxidation –
Ethylene glycol on oxidation with lead tetra
acetate (LTA) gives formaldehyde or methnal with
formation of acetic acid.
3c) Nitric acid oxidation - Ethylene glycol on
oxidation with nitric acid gives variety of products
depending on amount of acid used and reaction
conditions used which can be as follows,
CH2
CH2
OH OH
Pb(OAc)4 CH3COOH
- Pb(OAc)2
Ethylene glycol
+
Lead tetra acetate
H C
O
H
Methanal
+ 2
Acetic acid
Alcohols –Chemical reactions
CH2
CH2
OH OH
(O), HNO3
- H2
O
C CH2
O
OH
H
(O), HNO3
C CH2
O
OH
CHO
CHO
(O), HNO3
(O), HNO3 COOH
CHO
COOH
(O), HNO3
COOH
Ethylene glycol
2-hydroxy ethanal
Glycolic aldehyde
HO
2-hydroxy ethanaoic acid
Glycolic acid
Glyoxal Glyoxalic acid Oxalic acid
Ethane dioic acid
Ethanedial Oxoethanoic acid
Uses of Ethylene glycol – It is used as antifreeze agent, solvent,
coolant for aeroplane engines, in synthesis of polymers like
terylene, used as cream base for manufacture of cosmetic creams.

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Alcohols –Study of Pinacol
Formation of Pinacol (2,3-dimethyl, 2,3
butanediol)- When acetone is treated with metallic
magnesium (Mg) in presence of dry benzene it
gives pinacol. This reaction involves transfer of
single electron through formation of five member
transition state.
O
C
CH3
O
CH3
HgCl2
C
CH3 CH3
Mg++
Acetone
Benzene 333 K
.
Alcohols –Study of Pinacol
It occurs through following steps.
C
CH3
OH
C
OH
CH3
CH3
CH3
O
C
CH3 CH3
C
CH3 CH3
O , H2O
H+
- Mg(OH)2
. .
Mg++
Pinacol
Adduct
Alcohols :Pinacol-Pinacolone rearrangement
Pinacol-Pinacolone rearrangement – Acid
catalyzed conversion of 1,2-glycol into carbonyl
compounds through skeletal rearrangement of
carbocation intermediate is known as Pinacol-
Pinacolone rearrangement.
C
CH3
OH
C
OH
CH3
CH3
CH3
C
CH3
O
C CH3
CH3
CH3
H+
pinacolone
Pinacol
Alcohols :Pinacol-Pinacolone rearrangement
Pinacol-Pinacolone rearrangement – It invilves
following steps,
1.Protonation of hydroxyl group – It is reversible
reaction in which acid (H+) attacks lone pair of
electrons present on oxygen of hydroxyl group.
C
CH3
OH
C
OH
CH3
CH3
CH3
C
CH3
OH
C
OH2
CH3
CH3
CH3
Protonation
H+
+
Alcohols :Pinacol-Pinacolone rearrangement
2.Dehydration to produce carbocation - The
protonated hydroxyl group undergoes elimination
of water molecule to generate carbocation.
3. Intermolecular rearrangement of carbocation-
Carbocation generated undergoes intermolecuar
rearrangement to produce protonated ketone
C
CH3
OH
C
OH2
CH3
CH3
CH3
- H2
O
C
CH3
OH
C CH3
CH3
CH3
+
Dehydration
+
Carbocation
Alcohols :Pinacol-Pinacolone rearrangement
C
CH3
OH
C CH3
CH3
CH3
C
CH3
OH
C CH3
CH3
CH3
+
Carbocation
1,2 shift of CH3 group
+
:
C
CH3
OH
C CH3
CH3
CH3
C
CH3
OH
C CH3
CH3
CH3 +
Protonated ketone
+
:

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Alcohols :Pinacol-Pinacolone rearrangement
4. Deprotonation- Protonated ketone undergoes
deprotonation to produce pinacolon.
C
CH3
OH
C CH3
CH3
CH3
C
CH3
O
C CH3
CH3
CH3
H+
+
Protonated ketone pinacolone
Alcohols –Trihydric alcohols
Glycerol or Propane 1,2,3- triol
CH2
CH
OH
CH2
OH
OH
CH2
CH
OH
CH3
OH
OH
CH
Glycerol
1,2,3 -butane triol
Alcohols –Methods of formation
Glycerol or Propane 1,2,3- triol
1) Hydrolysis of oil or fat – Oil or fats are glycerol esters of
higher fatty acids. When they are subjected to alkaline
hydrolysis by saponifying alkali gives sodium or potassium
salt of higher fatty acid i.e. soap and glyerol.
It is colorless, odorless liquid with high viscosity and
B.P. = 563K. It is hygroscopic and soluble in water and
other alcohols.
CH2
CH
OH
CH2
OH
OH
CH2
CH
O-CO-R
CH2
O-CO-R
O-CO-R
R-COONa
3
NaOH, 353 K
Hydrolysis
+
Glycerol
Oil or Fat
Soap
Alcohols –Methods of formation
2) From Propene – Propene on chlorination gives 3-
chloro,1-propene, which on treatment with peroxy
compound like perbenzoic acid or hydrogen peroxide
forms epoxide.
This epoxide is treated with base to form
dihydroxy compound which on treatment with
aqueous sodium carbonate gives glycerol .
Chlorination Cl
C6H5COOOH
Cl
O
H
H
Cl
O
H
H
NaOH, H2
O
OH
Cl
OH
Na2
CO3
, H2
O
CH2
CH
OH
CH2
OH
OH
Glycerol
Alcohols –Methods of formation
3) From acrolein – Acrolein on selective reduction of
carbonyl group by M.P.V. reduction gives allyl alcohol. This
on treatment with peroxy compounds like perbenzoic acid
or hydrogen peroxide produces epoxide.
This epoxide is treated with base like NaOH to
form glycerol .
O
MPV Reduction C6
H5
COOOH OH
O
H
H
Acrolein
OH
OH
O
H
H
NaOH, H2O
CH2
CH
OH
CH2
OH
OH
Glycerol
Alcohols –Glycerol-Reactions
1.) Reaction with sodium metal (Na) - Glyecerol contains
three hydroxyl groups out of which two are primary –OH
groups and one is secondary –OH group.
When reacted with metallic sodium at room temperature
it forms monosodium derivative. Heating at higher
temperature produces disodium derivative where both
primary –OH groups react. It is not possible to from
sodium salt of secondary –OH group.
CH2
CH
OH
CH2
OH
OH
CH2
CH
ONa
CH2
OH
OH
CH2
CH
ONa
CH2
OH
ONa
Glycerol
Na, 298 K
Monosodium
glycerate
Disodium
glycerate
Na, 373 K

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Alcohols –Glycerol-Reactions
2.a) Reaction with HCl - When reacted with HCl at
383K it forms mixture of mono-chlorinated products
wherein one product is generated by replacement of
primary –OH group by Cl to produce 3-chloro, 1,2-
dihydroxy propane. Other product is generated by
replacement of secondary –OH group by Cl to
produce 2-chloro 1,3- dihydroxy propane.
CH2
CH
OH
CH2
OH
OH
- H2O
CH2
CH
Cl
CH2
OH
OH
CH2
CH
OH
CH2
Cl
OH
Major
Glycerol
HCl, 383K
3-chloro, 1,2-
dihydroxy propane
+
2-chloro, 1,3-
dihydroxy propane
Minor
Alcohols –Glycerol-Reactions
2.b) Reaction of HCl - When reacted with HCl at 383K in
excess of HCl it forms mixture of di-chlorinated products
wherein one product is generated by replacement of two
primary –OH groups by Cl to produce 1,3-dichloro, 2-
dihydroxy propane. Other product is generated by
replacement of one primary and one secondary –OH
group by Cl to produce 2,3-dichloro 1-hydroxy propane.
CH2
CH
OH
CH2
OH
OH
- H2O
CH2
CH
Cl
CH2
OH
Cl
CH2
CH
Cl
CH2
Cl
OH
Major
Glycerol
HCl, Excess
1,3-dichloro, 2-
hydroxy propane
+
2,3-dichloro, 1-
hydroxy propane
Minor
Alcohols –Glycerol-Reactions
3.a) Reaction with HI - When reacted with HI
glycerol forms tri-iodo derivative, glycerol tri-
iodide. This is unstable and decomposes to allyl
iodide (3-iodo, 1- propene) with libration of I2.
- I2
CH2
CH
OH
CH2
OH
OH
- H2
O
CH2
CH
I
CH2
I
I
CH2
CH
CH2 I
Glycerol
3H-I
Glyceryl
tri-iodide
Allyl iodide
Alcohols –Glycerol-Reactions
3.b) Reaction with HI - When reacted with excess of
HI glycerol forms tri-iodo derivative, which
decomposes to allyl iodide. This on reaction with HI
further forms 1,2-diiodopropane. This undergoes
elimination of I2 to produce propylene, this reacts
with HI to produce 2-iodopropane.
CH2
CH
OH
CH2
OH
OH
CH2
CH
CH2
I
CH3
CH
CH2
I
I
Allyl iodide
H-I Excess
Glycerol
1,2 di iodo
propane
CH3
CH
CH2
CH3
CH
CH3
I
Propene
H-I Addition
2-iodo Propane
CH3
CH
CH2
I
I
- I2
1,2 di iodo
propane
Alcohols –Glycerol-Reactions
4) Reaction with HNO3 - When reacted with nitric acid in
presence of mineral acid like H2SO4 at low temperature
glycerol forms trinitro derivatrive i.e. glycerol tri-nitrate.
Glycerol trinitrate is used in manufacture of dynamite as
it explodes on mild mechanical shock. It is also used in
production of pharmaceutical products used for
treatment of chest pain caused by reduced blood flow to
the heart.
CH2
CH
OH
CH2
OH
OH
HNO3
3
Conc. H2SO4
CH2
CH
ONO2
CH2
ONO2
ONO2
Glyceryl trinitrate
+
Glycerol
+ 3 H2O
Alcohols –Glycerol-Reactions
5) Reaction with KHSO4 - When reacted with
potassium hydrogen sulphate (KHSO4) glycerol
undergoes dehydration reaction, with elimionation of
two water molecules it produces acrolein.
Acrolein is used in manufacture of polymers,
heterocyclic compounds.
CH2
CH
OH
CH2
OH
OH
KHSO4
CHO
CH
CH2
Glycerol
+ 2 H2O
Acrolein

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Alcohols –Glycerol-Reactions
6) Reaction with acetic anhydride or acetyl chloriode
(Esterification of glycerol ) - When reacted with acetic
anhydride (CH3CO)2O or acetyl chloriode CH3COCl
glycerol under goes estrification reaction to produce
glycerol tri acetate.
CH2
CH
OH
CH2
OH
OH
(CH3CO)2O
OR CH3
COCl
CH2
CH
OCOCH3
CH2
OCOCH3
OCOCH3
Glycerol
+ 3 CH3COOH
Glyceryl triacetate
Alcohols –Glycerol-Reactions
7) Reaction with oxidizing reagents - When reacted
with oxidizing reagents like MnO2, Fentons reagent
(Fe+2 , H2O2), hypervalent iodine reagents glycerol
undergoes oxidation reaction to yield variety of
products. The primary –OH groups in glycerol are
oxidized to aldehyde (-CHO) group where as
secondary –OH group is oxidized to keton functional
group (-CO-). These carbonyl groups on further
oxidation form acid (-COOH). Acid on heating and
continual oxidation undergoes decarboxylation to
produce CO2 and water. This can be represented as
follows,
Alcohols –Glycerol-Reactions
CH2
CH
OH
CH2
OH
OH
- H2
O
CHO
CH
CH2
OH
OH
COOH
CH
CH2
OH
OH
COOH
CH OH
COOH
Glycerol
(O) (O) (O)
Glyceraldehyde Glyceric acid Tartronic acid
CH2
CH
OH
CH2
OH
OH
- H2
O
CH2
C=O
OH
CH2 OH
Glycerol
(O)
1,3-dihydroxy
2-propanone
COOH
CH OH
COOH
CH2
C=O
OH
CH2 OH
- H2O
COOH
C=O
COOH
COOH
COOH
Tartronic acid
OR
1,3-dihydroxy
2-propanone
(O)
Mesoxallic acid Oxalic acid
Phenols-Introduction
Phenols – Organic compounds in which hydroxyl (–OH)
group is directly attached the carbon of aromatic ring are
known as phenols.
They constitute one of most useful class of organic
compounds used in every day life. They are used as
disinfectants in soaps, hand washes and sanitizers. They
are also used in manufacture of polymers.
Depending on number of –OH groups directly attached to
aromatic ring they are classified as follows
OH
Phenol or
Carbolic acid
OH
CH3
3-methyl phenol
OH
NO2
2-nitro phenol
OH
NO2
4-nitro phenol
OH
NH2
2-Amino phenol
OH
Cl
2-Chloro phenol
Phenols- Classification
1) Monohydric phenols – Phenols containing only one
hydroxyl (–OH) group is directly attached the carbon of
aromatic ring are known as monohydric phenols.
2) Dihydric phenols – Phenols containing two hydroxyl (–
OH) groups is directly attached the carbon of aromatic
ring are known as dihydric phenols.
OH
Phenol or
Carbolic acid
OH
CH3
3-methyl phenol
OH
NO2
2-nitro phenol
OH
OH
Catechol
OH
OH
Resorcinol
OH
OH
Quinol
OH
OH
Br
m-bromo resorcinol
Phenols- Classification
3) Trihydric phenols – Phenols containing three hydroxyl
(–OH) groups is directly attached the carbon of aromatic
ring are known as trihydric phenols.
4) Polyhydric phenols – Phenols containing more than
three hydroxyl (–OH) groups is directly attached the
carbon of aromatic ring are known as polyhydric phenols.
OH
OH
OH
Pyrogallol
OH
OH
O
H
Phloroglycinol
OH
O
H
OH
Hydroxy quinol

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Phenols- Reactions
1) Acetylation phenols – Phenols on treatment with
acetyl chloride (CH3COCl) in presence of acid or base
undergo acetylation reaction wherein H from –OH group
is replaced by acetyl group (CH3CO) to produce phenyl
acetate.
Phenyl acetate is an important intermediate as it can be
used for synthesis of hydroxy ketones. This can be done
with Fries rearrangement using acid catalyst.
OH OCOCH3
- HCl
CH3COCl, NaOH
Phenol Phenyl acetate
Phenols- Reactions
2) Fries rearrangement – Acid catalyzed conversion
phenolic esters into ortho or para hydroxy ketones on
heating is known as Fries rearrangement. Generally acid
catalysts like AlCl3, ZnCl2, FeCl3 are used
Depending on the reaction conditions it gives different
products. At low temperature it gives p-substituted
product where as at high temperature it gives o-
substituted product. OH
COCH3
OCOCH3
OH
COCH3
o-hydroxy acetophenone
Phenyl acetate
Fries Rearrangement
298 K
438 K
p-hydroxy acetophenone
Phenols- Reactions
3)Etherification – Acidic nature of phenols can be used
for etherification reaction. In presence of strong base and
alkylating agents they undergo formation of phenolic
ethers.
3)a) Formation of methyl ether – Phenols on treatment
with dimethyl sulphate in basic medium produce phenyl
methyl ether popularly known as anisole.
OH OMe
(CH3)2SO4
K2CO3
CH3OSO3Na
Phenol Anisole
+ +
Phenols- Reactions
3)b) Formation of ethyl ether – Phenol on treatment with
ethyl chloride in basic medium produce phenyl ethyl
ether or ethoxybenzene.
3)c) Formation of benzyl ether - Phenol on treatment
with benzyl bromide in basic medium produce benzyl
phenyl ether.
OH OC2
H5
CH3CH2Cl
K2CO3
- HCl
Phenol
Ethoxy benzene
+
OH O-CH2-Ph
Br-CH2-Ph
K2
CO3
Phenol benzyl phenyl ether
+
- HBr
Phenols- Reactions
3)d) Formation of allyl ether – Phenol on treatment with
allyl bromide in basic medium produce phenyl allyl ether.
This can be used as important starting material for
synthesis of ortho or para allyl phenols which is popularly
known as Claisen Rearrangement.
Claisen Rearrangement – Conversion of aryl allyl ethers
into ortho or para substituted phenol on heating is
known as Claisen Rearrangement
OH O-CH2
-CH = CH2
Br-CH2
-CH =CH2
K2
CO3
Phenol Phenyl allyl ether
+ - HBr
Phenols- Reactions
4a) When ortho position of aryl allyl ether is not
substituted the allyl group migrates to produce o-allyl
phenols.
4b) When both the orto positions of aryl allyl ether are
having substitutions the allyl group migrates to produce
p-allyl phenols.
OH
CH2-CH = CH2
O-CH2-CH = CH2
o-allyl phenol
Phenyl allyl ether
473 K
OH
O-CH2
-CH = CH2
CH3
C
H3
O-CH2
-CH = CH2
CH3
C
H3
4-allyl, 2,6-dimethyl phenol
2,6 dimethyl
phenyl allyl ether
473 K

9. 10/18/2020
9
Phenols- Reactions
5) Gattermann reaction – Acid catalyzes conversion of
phenols into hydroxy aldehydes by treatment of hydrogen
cyanide (HCN) and hydrogen chloride (HCl) is known as
Gattermann reaction.
This is useful reaction for synthesis of phenolic aldehydes
it is also known as formylation reaction. This reaction
fails when phenols have electron withdrawing substitutes
like –NO2 group present on ring system.
OH
HCN
AlCl3
OH
CHO
OH
CHO
HCl
Phenol
o-hydroxy
benzaldehyd
e
+ +
p-hydroxy
benzaldehyd
e
Phenols- Reactions
6) Kolbe’s reaction (Caroxylation of phenols) –
Carboxylation of sodium salt of phenols in presence of
carbondioxide gas at high temperature.under high
pressure and is known as Kolbe’s reaction.
OH OH
COO-
ONa
CO2
Na
+
OH
COOH
Phenol Salicylic acid
NaOH
sodium salt
of phenol
423 K HCl
Phenols- Reactions
7) Reimer – Tiemann reaction : (Formylation of phenols)
– Base catalyzed conversion of phenols into ortho-
hydroxy or para-hydroxy aldehydes by treatment of
chloroform is known as Reimer – Tiemann reaction.
When carbon tetra chloride is used in place of CHCl3 it
produces acids in place of aldehydes.
OH
CHCl3
OH
CHO
OH
CHO
Phenol
NaOH
+
343 K
+
Salicyaldehyde p-hydroxy benzaldehyde
+ 3 KCl + 2H2O
OH
CCl4
OH
COOH
OH
COOH
Phenol
NaOH
+
343 K
+
p-hydroxy benzoicacid
Salicylic acid
4 KCl + 3H2O
+
Phenols- Reactions
Mechanism of Reimer – Tiemann reaction : Conversion
of phenols into o or p hydroxy aldehyde is known as RTR
This reactions involves following steps
a) Base catalyzed formation of dichlorocarbene
OH
CHCl3
OH
CHO
OH
CHO
Phenol
NaOH
+
343 K
+
Salicyaldehyde p-hydroxy benzaldehyde
+ 3 KCl + 2H2O
C
Cl
Cl
Cl
OH C
Cl
Cl
Cl
Cl
C
Cl
H +
Chloroform
Carbanion
- H2O
Cl
Dichlorocarbene
Phenols- Reactions
b) Generation of pohenoxide ion by reaction of phenol
and base followed by resonance of stabilization of
phenoxide ion.
OH O +
K
Phenol
KOH
- H2O
Potassium phenoxide
O O O O O
Phenols- Reactions
c) Electrophilic attack of dichlorocarbene on phenoxide
ion.
d) Hydrolysis of dichloro anion followed by dehydration of
phenoxide ion.
H
O
C
Cl
H
CCl2
O
CHCl2
O
Cl
Dichlorocarbene
+
CHCl2
O
CH(OH)2
O
CHO
O
2 KOH
- 2 HCl
- H2O

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Phenols- Reactions
e) Protonation of phenoxide ion to produce o-hydroy
benzaldehyde or salicyladehyde.
Application of Reimer – Tiemann reaction – Synthesis of
vanillin – when guaiacol is subjected to this reaction it
gives vanillin as one of the most used flavoring reagents
used in food industry.
CHO
O
CHO
OH
H+
Salicylaldehyde
OH
O-CH3
CHCl3
O-CH3
OH
CHO
Guaiacol
NaOH
+
343 K
Vanillin
Alcohols and Phenols - Classification
•Classification of alcohols
•Classification based on position of –OH group in
alkyl chain.
•Primary alcohols – In primary alcohols –OH
group is attached to primary carbon (carbon
attached to one more carbon atom). e.g.
•Ethyl alcohol:CH3CH2-OH,
•Propyl alcohol CH3CH2-CH2-OH
•Butyl alcohol CH3CH2-CH2-CH2-OH