12C11��Alcohols, Phenols and Ethers
Introduction to Alcohols, Phenols and Ethers
C
H
H
H
H
O
H
C
H
H
H
O
H
H
H
H
H
H
C
H
H
H
H
C
H
H
H
O
R
Aliphatic Hydrocarbon
Alcohol
Phenol
Ether
Benzene
Hydrocarbon
H
H
H
H
H
H
Why Alcohols, Phenols and Ethers ?
Industrial applications of compounds containing –OH group
Ether
Anesthesia
Solvent
12C11.1��Classification, Nomenclature and Structure
Learning Objectives
Classification of alcohols, phenols and ethers
Nomenclature of alcohols, phenols and ethers
Structure of alcohols, phenols and ethers
12C11.1 Classification, Nomenclature and Structure
12C11.1
CV 1
Classification of Alcohols, Phenols and Ethers
Classification of Alcohols
Mono-hydric
Di-hydric
Tri-hydric
Poly-hydric
1 –OH group
2 –OH group
3 –OH group
Many –OH groups
Ethanol
Ethylene glycol
Glycerol
Sorbitol
Mono-hydric Alcohols
1- Alkyl alcohol
2- Allylic alcohol
3- Benzylic alcohol
Vinylic alcohols
O
H
C
H
H
H
O
H
C
H
H
C
H
Alkyl alcohol
C
H
H
C
H
H
O
H
H
H
H
C
C
H
C
H
H
O
H
H
H
H
C
H
H
H
C
O
H
C
H
H
C
H
H
H
Allylic alcohol
Benzylic alcohol
Classification of Phenols
Mono-hydric
Di-hydric
Tri-hydric
1 –OH group
2 –OH group
3 –OH group
Phenol
Catechol
Resorcinol
Quinol
Phloroglucinol
Pyrogallol
Classification of Ethers
Simple or Symmetrical
Mixed or Unsymmetrical
alkyl or aryl groups attached to the oxygen atom are the same
alkyl or aryl groups attached to the oxygen atom are different
O
O
O
O
Dimethyl ether
Diphenyl ether
Ethyl methyl ether
Phenyl methyl ether
ConcepTest
Ready for Challenge
Q.
Classify the following as primary, secondary and tertiary alcohols.
Pause the video
Time duration: 1 minute
1
2
3
4
Sol.
1
2
3
4
Primary alcohol
Secondary alcohol
Tertiary alcohol
Secondary alcohol
12C11.1
CV 2
Nomenclature of Alcohols, Phenols and Ethers
Nomenclature of Alcohols
Common Names
Name of alkyl group + alcohol
Methyl alcohol
Ethyl alcohol
Iso-propyl alcohol
Pentyl alcohol
Neopentyl alcohol
Phenyl ethyl alcohol
Nomenclature of Alcohols
IUPAC Names
Suffix – “ol”
Methanol
Ethanol
Propan-2-ol
Pentan-2-ol
2,2-di-methylpropan-1-ol
1-Phenylethan-1-ol
1
2
3
1
2
3
4
5
1
2
3
Alkane
+ ‘ol’
1
2
Nomenclature of Alcohols
Pentan-2,3-di-ol
1
2
3
4
5
1
2
3
4
5
4-Chloro-2,3-dimethylpentan-1-ol
Cyclohexanol
2-Methylcyclopentanol
2
1
IUPAC Names
Suffix – “ol”
Alkane
+ ‘ol’
4-Chloro-2,3-dimethylpentanol
Nomenclature of Phenols
Common Names
Phenol
o-Cresol
m-Cresol
p-Cresol
Catechol
Resorcinol
Quinol
Nomenclature of Phenols
IUPAC Names
Phenol
2-Methylphenol
Benzene-1,2-diol
3-Methylphenol
4-Methylphenol
Benzene-1,3-diol
Benzene-1,4-diol
1
1
2
1
2
3
2
3
4
1
2
3
4
1
2
3
1
2
2-Hydroxyphenol
3-Hydroxyphenol
4-Hydroxyphenol
Nomenclature of Ethers
Common Names
Name of ‘R’ / ‘Ar’ group + ether
Dimethyl ether
Methyl phenyl ether
Methyl isopropyl ether
Phenyl propyl ether
Ethyl methyl ether
Anisole
Diphenyl ether
Ethyl phenyl ether
Phenetole
IUPAC Names
Smaller ‘R’ / ‘Ar’ + oxy + bigger alkyl chain
Methoxymethane
Methoxybenzene
2-Methoxypropane
2-Methoxy-1,1-dimethylcyclohexane
Anisole
Ethoxybenzene
Methoxyethane
1,2-Dimethoxyethane
Nomenclature of Ethers
1
2
3
2
1
2
1
12C11.1
PSV 1
Q.
Write the IUPAC names of the following compounds
Pause the video
Time duration: 1 minute
Sol.
Hex-1-en-3-ol
2-Bromo, 3-methylbut-2-en-1-ol
2,6-Dimethylphenol
1
3
2
4
5
6
1
2
3
4
1
2
3
4
6
5
1
3
2
4
5
1
3
2
4
5
2,5-Dimethylhexan-1,3-di-ol
6
O-Nitroanisole
3-Chloromethyl-2-isopropylpentan-1-ol
o
12C11.1
CV 3
Structure of Alcohols, Phenols and Ethers
Structure of Alcohols
O
C
H
H
H
H
.
.
.
.
O
R
H
Methanol
Structure of Phenol
.
.
C-O bond length in phenol < C-O bond length in methanol
O
H
.
.
Structure of Ether
O
R
R
O
C
H
H
H
.
.
.
.
Methoxymethane
C
H
H
H
Bond angle is slightly greater than the tetrahedral angle due to repulsive interaction between two bulky (–R) groups.
12C11.1
PSV 2
Q.
Pause the video
Time duration: 1 minute
Why does the C-O bond length in phenol is smaller than that of C-O bond length in methanol ?
Q.
Why does the C-O bond length in phenol is smaller than that of C-O bond length in methanol ?
Sol.
Partial double bond character on account of the conjugation of
unshared electron pair of oxygen with the aromatic ring
.
.
.
.
.
.
.
.
Summary
Alcohols
Mono-hydric
Di-hydric
Tri-hydric
Poly-hydric
1- Alkyl alcohol
2- Allylic alcohol
3- Benzylic alcohol
Vinylic alcohols
Phenol
Mono-hydric
Di-hydric
Tri-hydric
Simple or Symmetrical
Mixed or Unsymmetrical
Ethers
IUPAC Nomenclature
Alcohols
-ol
Phenols
Ethers
-oxy
Reference Questions
NCERT Exercise Questions: 11.1, 11.23
Workbook Question: 1
12C11.1 Alcohols, Phenols and Ethers
NCERT Intext Questions: 11.1, 11.2, 11.3
12C11.2��Preparation of Alcohols
Learning Objectives
Preparation of Alcohols from Alkenes
Preparation of Alcohols from carbonyl compounds
Preparation of Alcohols from Grignard reagent
12C11.2 Preparation of Alcohols
12C11.2
CV 1
Preparation of Alcohols from Alkenes
Preparation of Alcohols from Alkenes
By acid catalysed hydration
By hydroboration–oxidation
By acid Catalysed Hydration
Symmetrical alkene
Unsymmetrical alkene
Markovnikov’s rule
Mechanism
Step - 1
Hydronium ion
carbocation
Mechanism
Step - 2
Step - 3
Nucleophilic attack of water on carbocation
Deprotonation to form an alcohol
Alcohol
By Hydroboration–oxidation
1.
2.
Alkene
Alcohol
Feature of the reaction
Product seems opposite to the Markovnikov’s rule
Alcohol is obtained in excellent yield
or
Mechanism
Steps repeat
Tetravalent transition state
Trialkyl borane
Electron deficient
Formation of hydroperoxide ion
Nucleophilic addition
Nucleophile
Mechanism
1-2 Alkyl shift from boron to oxygen
Hydrolysis of trialkoxyborane
Trialkoxyborane
Mechanism
12C11.2
PSV 1
Q. Find the products of the following reaction.
Pause the video
Time duration: 1 minute
1.
2.
Sol.
1.
2.
Steps repeat
12C11.2
CV 2
Preparation of Alcohols from Carbonyl compounds
Alcohols from Carbonyl Compounds
By reduction of aldehydes and ketones
By reduction of carboxylic acids and esters
Aldehydes
Reducing agent
and
Ketones
?
Reduction of Aldehydes and Ketones
Reduction of Aldehydes and Ketones
Aldehyde
1° Alcohol
Ketone
2° Alcohol
Feature- can reduce
Reduction of Aldehydes and Ketones
Aldehyde
1° Alcohol
Ketone
2° Alcohol
Feature
Can reduce aldehyde, ketone and carboxylic acid
Highly sensitive to moisture
Can not reduce C=C double bond
Reduction of Aldehydes and Ketones
Aldehyde
1° Alcohol
Ketone
2° Alcohol
Feature
Other functional groups like halogen, cyano remain unaffected
Can not reduce C=C double bond
Reduction of Carboxylic acids and Esters
1° Alcohol
Oic acid
Ester
Aldehyde
Reduction of Carboxylic acids and Esters
Esterification and then catalytic reduction
1° Alcohol
Oic acid
Ester
12C11.2
PSV 2
Q. Find the products A and B in the following reactions.
Pause the video
Time duration: 1 minute
Sol.
Crotonaldehyde
n-Butyl alcohol
Crotonaldehyde
Crotyl alcohol
12C11.2
CV 3
Preparation of Alcohols from Grignard reagent
Grignard Reagent:
Mg
X
R
Alkyl or aryl group
It can form-
1° Alcohol
Formaldehyde
2° Alcohol
Aldehyde
3° Alcohol
Ketone
Preparation of Alcohols from Grignard reagent
Nucleophilic addition of Grignard reagent to the carbonyl group
Mechanism
Adduct
Formaldehyde
Nucleophilic addition of Grignard reagent to the carbonyl group
Mechanism
Adduct
Aldehyde
ConcepTest
Ready for Challenge
Pause the video
Time duration: 1 minute
Q.
How will you prepare 2-Methylprop-2-ol with the help of Grignard reagent.
Sol.
Adduct
Acetone
2-Methylprop-2-ol
1.
2.
Alkene
Alcohol
Aldehyde
Ketone
Grignard Reagent:
Summary
Reference Questions
NCERT Exercises: 11.11, 11.20, 11.32
Workbook Question: 15, 17 (i) and (iii)
12C11.2 Preparation of Alcohols
NCERT Intext Questions: 11.4, 11.5
Reference Questions
NCERT Exercises: 4.24, 4.25, 4.26, 4.27, 4.28 and 4.29
Workbook Question: 12, 18 and 20
11C04.4 Hybridisation
12C11.3��Preparation of Phenols
Learning Objectives
Preparation of phenols – part 1
Preparation of phenols – part 2
12C11.3 Preparation of Phenols
12C11.3
CV 1
Preparation of Phenols – Part 1
Preparation of Phenols
Carbolic acid
First isolated from coal tar
In laboratory, phenols are prepared from
benzene derivatives
Phenols from Haloarenes
Chlorobenzene
Sodium phenoxide
Phenol
Dows process
Nucleophilic substitution reaction
Phenols from Benzene sulphonic acid
Benzene
Benzene sulphonic acid
Phenol
12C11.3
PSV 1
Q. Explain the mechanism for the following reaction.
Pause the video
Time duration: 1 minute
Chlorobenzene
Sodium phenoxide
Phenol
Mechanism
Nucleophile
Chlorobenzene
Sodium phenoxide
Phenol
Phenol
12C11.3
CV 2
Preparation of Phenols – Part 2
Phenols from Diazonium salts
Aniline
Benzene diazonium chloride
Phenol
Benzene diazonium salt from aniline - Diazotisation
Warm
Phenols from Cumene
Cumene
Isopropyl benzene
Cumene
hydroperoxide
Phenol
Acetone
Acid catalyzed reaction
Yield of acetone is also good
12C11.3
PSV 2
Q. Explain the mechanism for the following reaction.
Pause the video
Time duration: 1 minute
Aniline
Phenol
Mechanism
Electrophile
Formation of electrophile
Mechanism
Formation of Benzene diazonium salt
Aniline
Mechanism
Formation of Benzene diazonium salt
or
or
Mechanism
Phenol from Benzene diazonium salt
Heat
Phenol
Benzene diazonium chloride
Summary
Benzene
Benzene sulphonic acid
Phenol
Chlorobenzene
Phenol
Cumene
Phenol
Aniline
Phenol
Reference Questions
NCERT Exercises: 11.9, 11.10, 11.12,
Workbook Question: 2
12C11.3 Preparation of Phenols
12C11.4��Properties of Alcohols and Phenols – Part 1
Learning Objectives
12C11.4 Properties of Alcohols and of Phenols – Part 1
Physical properties of alcohols and phenols
Chemical properties of Alcohols and Phenols
Acidity of Phenols
Esterification
12C11.4
CV 1
Physical properties of Alcohols and Phenols
Physical properties of Alcohols and Phenols
Alkyl or aryl group
Responsible for most of the properties
Responsible for modification in properties
Boiling points of Alcohols and Phenols
B.P of alcohols and phenols increase with increase in the number of carbon atoms
No. of carbon atoms
van der Waals forces
B.P
High Van der Waals forces
High boiling point
Boiling points of Alcohols and Phenols
Boiling points decrease with increase of branching in carbon chain
Branch
Surface area
6-C
van der Waals forces
B.P
6-C
Low Van der Waals forces
Low boiling point
Boiling points of Alcohols and Phenols
B.P of alcohols and phenols are higher than hydrocarbons, ethers, haloalkanes and haloarenes of comparable molecular masses
Ethanol = 46
Dimethyl ether = 46
Propane = 44
B.P = 351 K
B.P = 248 K
B.P = 231 K
Boiling points of Alcohols and Phenols
Reason of high B.P of alcohols and phenols
H – bonding
H – bonding
Solubility of Alcohols and Phenols
Alcohols and phenols are soluble in water due to H – bonding
solubility decreases with
increase in size of alkyl/aryl group
Hydrophobic
Hydrophilic
Bigger Hydrophobic part
Smaller Hydrophobic part
Low solubility
High solubility
ConcepTest
Ready for Challenge
Q. Arrange the following compounds in order of their increasing b.p.
Pentan-1-ol, butan-1-ol, butan-2-ol, ethanol, propan-1-ol, methanol
Pause the video
Time duration: 1 minute
Decreases with increase of branching in carbon chain.
Methanol
Ethanol
Propan-1-ol
Butan-2-ol
Butan-1-ol
Pentan-1-ol
Sol.
Increases with increase in the no. of C-atoms.
Boiling points of alcohols -
<
<
<
<
<
12C11.4
CV 2
Chemical properties of Alcohols and Phenols
Alcohols are versatile compounds
Act as nucleophile
Act as electrophile
bond between O–H will break
bond between C–O is break
Alcohols as Nucleophile
Alcohol
Carbocation
Unstable
Ether
Nucleophile
Alcohols as Electrophile
Protonated alcohols react in this manner
Alcohol
Hydrogen ion
Unstable
Alkyl halide
Halide ion
Reactions involving cleavage of O–H bond
Acidity of alcohols
Esterification
Acidity of phenols
Acidity of Alcohols
Reaction with metals
Alcohol
Sodium alkoxide
tert- butyl Alcohol
Aluminium tert-butoxide
Act as a Bronsted acid
Alcohol
Base
Conjugate acid
Brönsted acids
Conjugate base
Acidity of Alcohols
Acidity of alcohols is due to polar nature of –OH bond
Order of acidity of alcohols
R group is decreasing the polarity of O-H bond
Acidity of Alcohols
12C11.4
PSV 1
Q. Compare the acidic character of alcohols and water.
Pause the video
Time duration: 1 minute
Alcohols are weaker acids than water
Sol.
Proton donor
Water
Alkoxide ion
Proton accepter
Stronger base
Conjugate base
Conjugate acid
Alkoxide ion
Weaker acid
12C11.4
CV 3
Acidity of Phenols
Acidity of Phenols
Reaction with metals
Phenol
Sodium phenoxide
More stable
More acidic
More favorable
High concentration
More stable due to resonance
Resonance in phenol
Acidity of Phenols
Resonance in Phenoxide ion
Phenol
Resonance in phenol
Phenoxide ion
Phenoxide ion is stable due to resonance
Thus, phenol is acidic in nature
Resonance in Phenoxide ion
Acidic nature of Alcohol vs Phenol
More stable due to resonance
More acidic
More favorable
High concentration
Alkoxide ion
Alcohol
Phenol
Phenoxide ion
Low concentration
Less acidic
Slow
Fast
Acidic nature of Substituted Phenol
Effect of electron withdrawing groups
Effect of electron donating groups
Effect of electron withdrawing groups
This effect is more pronounced when such a group is present at ortho and para positions
Increase the acidic nature of phenol
o-Nitrophenol
p-Nitrophenol
m-Nitrophenol
Decreases with distance
More pronounced
Effective delocalisation of negative charge in phenoxide ion
Effect of electron donating groups
Decrease the acidic nature of phenol
m-Cresol
p-Cresol
Hyper conjugation
Will not work at –m position
Inductive effect
o-Cresol
Near to –OH group
ConcepTest
Ready for Challenge
Q. Compare the acidic nature of following compounds.
Pause the video
Time duration: 1 minute
o-Nitrophenol
p-Nitrophenol
m-Nitrophenol
O-Cresol
m-Cresol
p-Cresol
Phenol
Sol.
Nitro
Acidic nature
Cresol
Alkyl
Phenol
Nitrophenol
Electron withdrawing group
Electron donating group
o-Nitrophenol
p-Nitrophenol
m-Nitrophenol
Phenol
p-Cresol
m-Cresol
o-Cresol
(-R)
Hyper conjugation
Hyper conjugation
12C11.4
CV 4
Esterification
Esterification
Carboxylic acids
or
Acid chlorides
or
Acid anhydrides
Alcohol
or
Phenol
Ester
Catalyst
Oic acid
Acid chloride
Acid anhydride
Mechanism
Oic Acid
Protonated acid
Deprotonation
Ester
Acetylation
Salicylic acid
Acetic anhydride
Acetylsalicylic acid
Acetic acid
Aspirin
Synthesis of Aspirin
Used to treat fever and pain
Summary
Reason of high B.P of alcohols and phenols
H – bonding
Reason of solubility of alcohols and phenols in water
H – bonding
Alcohol can act as nucleophile
bond between O–H will break
Acidity of alcohols
Esterification
Acidity of phenols
E.W.G
Increase acidity
E.D.G
Decrease acidity
Oic acid + alcohol
Ester
Reference Questions
NCERT Exercises: 11.4, 11.5, 11.14, 11.15
Workbook Question: 6, 9
12C11.4 Properties of Alcohols and Phenols – Part 1
12C11.5��Properties of Alcohols and Phenols – Part 2
Learning Objectives
12C11.5 Properties of Alcohols and of Phenols – Part 2
Dehydration of alcohols
Oxidation of alcohols
Alcohols as Electrophile
Protonated alcohols react in this manner
Alcohol
Hydrogen ion
Unstable
Alkyl halide
Halide ion
Bond between C–O will break
Reaction with hydrogen halides
Boiling Alcohol
Hydrogen halide
Alkyl halide
Water
Ethanol
Hydrogen chloride
Ethyl chloride
Water
Order of reactivity
Tertiary
Secondary
Primary
>
>
Remove
Lucas Test
Immediate turbidity
Turbidity within 5 min.
No turbidity or on heating
Colourless
Reaction with Phosphorus tri halides
Alcohol
Phosphorus tri halide
Alkyl halide
Methyl alcohol
Phosphorus tri chloride
Methyl chloride
Phosphoric acid
Phosphoric acid
12C11.5
CV 2
Dehydration of Alcohols
Dehydration –
Removal of water molecule
Dehydration –
Removal of water molecule
443 K
440 K
Ethanol
Propen-2-ol
2-Methyl propen-2-ol
358 K
Ease of dehydration -
Tertiary
Secondary
Primary
Mechanism
Dehydration of Ethanol
Fast
Slow
Ethanol
Protonated ethanol
Step - 2
Formation of carbocation
Step - 3
Elimination of proton
Ethene
Step - 1
Protonation of alcohol
Ethyl carbocation
12C11.5
PSV 1
Q.
Find the major product for the following reaction.
Pause the video
Time duration : 1 minute
. .
. .
1,2 Hydride Shift
Sol.
2,3-Dimethylbut-2-ene
12C11.5
PSV 2
Q.
Find the major product for the following reaction.
Pause the video
Time duration : 1 minute
Sol.
But-1-ene
Minor
But-2-ene
Major
Saytzeff rule
More substituted alkene will be major product
ConcepTest
Ready for challenge
Q. Predict the major product of acid catalysed dehydration of
1-Methylcyclohexanol.
Pause the video
Time duration: 2 minute
Sol.
Major
Minor
According to Saytzeff rule
1-Methylcyclohexanol
Unstable
12C11.5
CV 3
Oxidation of Alcohols
Oxidation of Alcohols
Alcohol
Aldehyde
Oxidation of alcohols involves -
Also called as dehydrogenation reactions
Oxidise
Oxidation of Alcohols
Oxidation of primary alcohols
Oxidation of secondary alcohols
Oxidation of tertiary alcohols
Oxidation of Primary Alcohols
Primary alcohol
Aldehyde
Carboxylic acid
Oxidation
Oxidation
Strong Oxidation
Aldehyde
Oxidation
Oxidation
Alcohol
Carboxylic acid
Strong oxidising agent
Aldehyde
Cu, 573 K
Alcohol
Oxidation of Primary Alcohols
Best reagent for oxidation of primary alcohols into aldehyde
PCC
Primary Alcohol
Aldehyde
PCC = Pyridinium chlorochromate
Chromium trioxide
Pyridine
Hydrogen chloride
Oxidising agent
Oxidation of Secondary Alcohols
Secondary Alcohol
Ketone
Secondary Alcohol
Ketone
Cu, 573 K
or
Oxidation of Tertiary Alcohols
Dehydration
Cu 573 K
Do not undergo oxidation
Tertiary alcohol
Ketone
O
Undergo dehydration in place of dehydrogenation with Cu at 573 K
Tertiary alcohol
Alkene
Cu 573 K
Reaction with Cu at 573 K
Ethanol
Denatured alcohol
Methanol
Ethanol is used for drinking purpose
Poison
Methanal
Methanoic acid
Biological oxidation
Can cause Blindness
+
Summary
Lucas Test
Alcohol
Phosphorus tri halide
Alkyl halide
Phosphoric acid
Ease of dehydration -
Tertiary
Secondary
Primary
PCC
Primary Alcohol
Aldehyde
Oxidation of Alcohol
Reference Questions
NCERT Exercises: 11.13, 11.17 (i), 11.19, 11.21 (i), (ii), (iv), (v), 11.33
Workbook Question: 10, 16 (i), 19
12C11.5 Properties of Alcohols and Phenols – Part 2
NCERT Intext Questions: 11.6 (a) and (b), 11.7
12C11.6��Reactions of Phenols
and
Important Alcohols
Learning Objectives
12C11.6 Reactions of Phenols and Important Alcohols
Electrophilic aromatic substitution reactions of Phenols
Kolbe’s reaction and Reimer –Tiemann reaction
Nitration and Halogenation
Some Commercially Important Alcohols
12C11.6
CV 1
Electrophilic Aromatic Substitution Reactions of Phenols
Phenoxide ion
Resonance in Phenoxide ion
Electrophile
C
C
C
C
C
H
H
H
H
H
C
OH
-o and -p are the more favourable sites for electrophilic attack
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
OH
H
H
H
H
H
E
C
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
OH
H
H
H
H
H
E
C
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
E
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
C
H
H
H
H
H
E
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
H
H
H
H
H
E
C
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
H
H
H
H
H
E
C
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
H
H
H
H
E
C
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
H
H
H
H
E
C
C
OH
Electrophilic Aromatic Substitution in Phenols
C
C
C
C
H
H
H
H
E
C
C
OH
Electrophilic Aromatic Substitution in Phenols
12C11.6
CV 2
Nitration and Halogenation
Nitration of Phenol
Phenol
o-Nitrophenol
p-Nitrophenol
Protonated nitric acid
Nitronium ion
Acid
Base
Electrophile
Nitration of Phenol
o-Nitrophenol
p-Nitrophenol
Intramolecular H-bonding
Steam volatile
Intermolecular H-bonding
Low b.p
High b.p
Less volatile
ortho and para isomers can be separated by steam distillation
Phenol
2,4,6 - Trinitrophenol
Picric acid
Halogenation of Phenol
Solvents of low polarity
Solvents of high polarity
Mono halogenated products
2,4,6 substituted product
Bromination in Solvents of low Polarity
Phenol
o-Bromophenol
p-Bromophenol
Bromination in Solvents of high polarity
Phenol
2,4,6-Tribromophenol
12C11.6
PSV 1
Q. Write the structures of the major products expected from the
following reactions:
(a) Mononitration of 3-Methylphenol
(b) Dinitration of 3-Methylphenol
Pause the video
Time duration : 1 minute
Sol.
+
12C11.6
PSV 2
Q.
Give mechanism of the following reaction.
Pause the video
Time duration : 1 minute
Sol.
Phenol
o-Bromophenol
12C11.6
CV 3
Kolbe’s Reaction
and
Reimer – Tiemann Reaction
Kolbe’s Reaction
Phenol
Salicylic Acid
Sodium phenoxide
o-hydroxybenzoic acid
Feature-
An example of carboxylation reaction
Reimer – Tiemann Reaction
o-Salicylaldehyde
Phenol
p-Salicylaldehyde
Feature-
-o product will be major product
-o and –p products can be separated by steam distillation
Mechanism Reimer –Tiemann Reaction
Chloroform
Dichloro carbene
Formation of Electrophile
Electrophile
O
H
Cl
Cl
_
Cl
Cl
H
O
Cl
H
H
OH
O
H
Mechanism Reimer –Tiemann Reaction
Leaving group
o-Salicylaldehyde
Reaction of Phenol with Zinc Dust
Phenol is converted to benzene on heating with zinc dust
+
Zn
+
ZnO
Phenol
Benzene
Oxidation of Phenols
Oxidation of phenol with chromic acid produces a conjugated diketone known as benzoquinone
Phenol
Benzoquinone
12C11.6
PSV 3
Q. Give mechanism of Kolbe’s reaction.
Pause the video
Time duration : 1 minute
Phenol
Salicylic acid
Sodium phenoxide
Mechanism of Kolbe’s Reaction
Phenol
Salicylic Acid
Phenoxide ion
o-hydroxybenzoic acid
Sol.
12C11.6
CV 4
Some Commercially Important
Alcohols
Methanol or Wood spirit
Preparation
1. Destructive distillation of wood
2. Catalytic hydrogenation of carbon monoxide
Wood in Retort
Coal gas
Coal
Mix. Of liquids
Methanol
Properties and Uses of Methanol
Colourless liquid
B.P is 337 K
Poisonous in nature -
Can cause blindness or death
Used as a solvent in paints, varnishes
For making formaldehyde
Properties
Uses
Ethanol
Preparation
Commercially - Fermentation
Sugar
Glucose
Fructose
Invertase
Ethanol
Zymase
Properties and Uses of Ethanol
Colourless liquid
B.P is 351 K
Solvent in paints industry
For making large no. of organic compounds
Properties
Uses
Denaturation of alcohol
Commercial alcohol is made unfit for drinking
Ethanol
Copper sulphate
Coloured alcohol
Pyridine
Foul smell
12C11.6
PSV 4
Q. How wine is formed from grapes?
Pause the video
Time duration : 1 minute
Sol.
Sugar
Glucose
Fructose
Invertase
Ethanol
Zymase
Yeast
12C11.6
PSV 5
Q. Fermentation takes place in anaerobic conditions. Why?
Pause the video
Time duration : 1 minute
Sol.
Sugar
Glucose
Fructose
Invertase
Ethanol
Zymase
In anaerobic conditions
Ethanoic acid
Oxidation
Taste of alcohol will destroy
Summary
-o and -p are the more favourable sites for electrophilic attack
o-Nitrophenol
p-Nitrophenol
Nitration
o-Bromophenol
p-Bromophenol
Bromination
Methanol
Destructive distillation
Ethanol
Fermentation
Reference Questions
NCERT Exercises: 11.17 (i), (ii), (iii), 11.18 (i), (ii), 11.21 (iii),
Workbook Question: 5, 7, 8, 11 (i), 13 (ii), 20
12C11.6 Reactions of Phenols and Important Alcohols
NCERT Intext Questions: 11.9
12C11.7
Ethers
Learning Objectives
Preparation of Ether
Physical properties of Ether
Chemical properties of Ether
12C11.7 Ethers
12C11.7
CV 1
Preparation of Ether
Preparation of Ether
By dehydration of Alcohol
Williamson Ether synthesis
Ethanol
Ethene
Ethoxy ethane
By Dehydration of Alcohol
Step 1:
.
.
.
.
+
Step 2:
.
.
.
.
+
Step 3:
Protonated Alcohol
Ethoxy ethane
Mechanism
By Dehydration of Alcohol
Suitable for the preparation of ethers having primary alkyl groups only
Alkene
Dehydration
( major product )
Ether
Dehydration
( major product )
By Dehydration of Alcohol
Alkyl group should be unhindered
Temperature should be low
Conditions -
Williamson Ether Synthesis
.
.
.
.
.
.
.
.
-
+
Mechanism
+
-
.
.
.
.
.
.
.
.
Alkyl Halide
Sodium Alkoxide
Ether
2-Methyl propoxide
Methyl bromide
2-Methyl-2-methoxy propane
In case of secondary and tertiary alkyl halides, elimination dominates over substitution.
-
+
.
.
.
.
Williamson Ether Synthesis
If a tertiary alkyl halide is used, an alkene is the only reaction product and no ether is formed
Phenols are also converted to ethers by this method
+
NaOH
Williamson Ether Synthesis
Phenol
Sodium phenoxide
Ether
12C11.7
PSV 1
Write the reactions of Williamson synthesis of 2-Ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.
Q.
Pause the video
Time duration : 1 minute
Write the reactions of Williamson synthesis of 2-Ethoxy-3-methylpentane starting from ethanol and 3-methylpentan-2-ol.
Sol.
|
|
|
|
|
|
+
+
|
|
2-Ethoxy-3-methylpentane
+
Ethanol
Bromo Ethane
3-Methyl-pent-2-ol
3-Methyl-sodium pentoxide
3-Methyl-sodium pent-oxide
Q.
12C11.7
CV 2
Physical properties of ether
Physical properties of ether
Alkanes and ethers of comparable molecular mass have similar boiling point due to weak polarity of ether bonds
Formulae | | | |
name | n-pentane | Ethoxyethane | Butan-1-ol |
b.p./K | 309.1 | 307.6 | 390 |
The large difference in boiling points of alcohols and ethers is due to the presence of hydrogen bonding in alcohols.
12C11.7
CV 3
Chemical properties of Ether
Ethers are less reactive so cleavage of C-O bond in ethers takes place under drastic conditions with excess of hydrogen halides
+
+
+
+
Ether
Alcohol
Alkyl halide
Alcohol
Alkyl halide
R
R’
>
Halide will combine with smaller alkyl group
Alkyl aryl ethers are cleaved at the alkyl-oxygen bond due to the more stable aryl-oxygen bond to give phenol and alkyl halide
+
Alkyl aryl ether
Alkyl phenyl oxonium ion
Alkyl aryl ethers are cleaved at the alkyl-oxygen bond due to the more stable aryl-oxygen bond to give phenol and alkyl halide
+
Alkyl aryl ether
+
Phenol
Alkyl halide
Alkyl phenyl oxonium ion
Reactivity order of HX towards Ether
Reactivity Order :
Bond
Length
<
<
<
<
Mechanism :
Step 1:
Protonation of ether molecule
+
.
.
.
.
+
+
Step 2:
+
Methoxy ethane
Methyl iodide
Ethanol
.
.
+
.
.
+
Step 3 :
Ethanol reacts with another molecule of HI and is converted to ethyl iodide.
.
.
.
.
+
.
.
+
+
+
+
+
Mechanism :
Ethanol
Protonated ethanol
Ethyl iodide
When one of the alkyl group is a tertiary group, the halide formed is a tertiary halide
+
+
2-Methyl 2-methoxy propane
Methanol
2-Iodo 2-methyl propane
.
.
Phenoxide ion
.
.
.
.
.
.
.
.
.
.
.
.
Friedel - Crafts Alkylation
Alkyl groups are introduced at ortho and para positions by reaction with alkyl halide in the presence of anhydrous aluminium chloride as catalyst
Halogenation
Anisole undergoes bromination with bromine in ethanoic acid even in the absence of iron (III) bromide catalyst due to activation of benzene ring by methoxy group
+
Anisole
p-Bromoanisole
o-Bromoanisole
Para isomer is obtained in 90% yield.
Friedel - Crafts Alkylation
Alkyl groups are introduced at ortho and para positions by reaction with alkyl halide in the presence of anhydrous aluminium chloride as catalyst
Anisole
2-Methoxy-toulene
4-Methoxy-toulene
Methyl Chloride
+
+
Friedel - Crafts Alkylation
Step 1:
Mechanism :
Step 2:
Formation of electrophile
Attack of electrophile to benzene ring
H
|
|
H
..
..
..
+
H
|
|
H
+
+
+
+
Friedel - Crafts Alkylation
Step 3 :
Positive charge formed on carbocation is delocalized throughout the molecule
+
+
+
Mechanism :
Aromaticity is restored by the loss of a proton from the atom to which the methyl group has bonded.
Friedel - Crafts Alkylation
Step 4 :
+
Step 5 :
+
+
Mechanism :
Friedel - Crafts Acylation
Anisole
2-Methoxy-acetophenone
(Minor)
4-Methoxy-acetophenone
(Major)
Ethonyl chloride
+
+
Electrophile
Generation of Electrophile :
Nitration
Anisole
2-Nitro anisole
(Minor)
4-Nitro anisole
(Major)
+
. .
. .
. .
Protonated nitric acid
Acid
Base
. .
Nitronium ion
Unstable
Electrophile
Generation of Nitronium ion :
12C11.7
PSV 2
Give the major products that are formed by heating each of the following ethers with HI.
(i)
(ii)
Q.
(i)
(ii)
+
+
Sol.
Propan-1-ol
2-Iodo 2-methyl butane
Phenol
Benzyl chloride
Summary
By Dehydration of Alcohol
Ether
Dehydration
( major product )
Williamson Ether Synthesis
.
.
.
.
.
.
.
.
-
+
Alkyl Halide
Sodium Alkoxide
Ether
+
+
Ether
Alkyl halides
Reactivity order of HX towards Ether
<
<
Summary
+
Anisole
p-Bromoanisole
o-Bromoanisole
+
Alkyl aryl
ether
+
Phenol
Alkyl halide
Alkyl phenyl
oxonium ion
Halogenation :
Summary
Anisole
2-Methoxy-toulene
4-Methoxy-toulene
Methyl Chloride
+
+
Anisole
2-Methoxy-acetophenone
(Minor)
4-Methoxy-acetophenone
(Major)
Ethonyl chloride
+
+
Anisole
2-Nitro anisole
(Minor)
4-Nitro anisole
(Major)
+
Friedel - Crafts Acylation
Friedel - Crafts Alkylation
Nitration
Reference Questions
NCERT Exercises: 4.24, 4.25, 4.26, 4.27, 4.28 and 4.29
Workbook Question: 12, 18 and 20
12C11.7 Reactions of Phenols and Important Alcohols