Concepts - Alcohols, Phenols & Ethers Class 12 Notes | EduRev

Class 12 : Concepts - Alcohols, Phenols & Ethers Class 12 Notes | EduRev

 Page 1


 1
Class XII: Chemistry 
Chapter 11: Alcohols, Phenols And Ethers 
Top Concepts 
1. Structure of alcohols, phenols and ethers:  
  
2.  Preparation of alcohols: 
  
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 1
Class XII: Chemistry 
Chapter 11: Alcohols, Phenols And Ethers 
Top Concepts 
1. Structure of alcohols, phenols and ethers:  
  
2.  Preparation of alcohols: 
  
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 2
3. Preparation of phenols: 
               
4. Physical properties of alcohols and phenols: 
a. Boiling points:  
• Boiling points of alcohols and phenols are higher in comparison to other 
classes of compounds, namely hydrocarbons, ethers, haloalkanes and 
haloarenes of comparable molecular masses. This is because the –OH 
group in alcohols and phenols is involved in intermolecular hydrogen 
bonding. 
 
• The boiling points of alcohols and phenols increase with increase in the 
number of carbon atoms. This is because of increase in van der Waals 
forces with increase in surface area.  
• In alcohols, the boiling points decrease with increase of branching in 
carbon chain. This is because of decrease in van der Waals forces with 
decrease in surface area. 
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Class XII: Chemistry 
Chapter 11: Alcohols, Phenols And Ethers 
Top Concepts 
1. Structure of alcohols, phenols and ethers:  
  
2.  Preparation of alcohols: 
  
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 2
3. Preparation of phenols: 
               
4. Physical properties of alcohols and phenols: 
a. Boiling points:  
• Boiling points of alcohols and phenols are higher in comparison to other 
classes of compounds, namely hydrocarbons, ethers, haloalkanes and 
haloarenes of comparable molecular masses. This is because the –OH 
group in alcohols and phenols is involved in intermolecular hydrogen 
bonding. 
 
• The boiling points of alcohols and phenols increase with increase in the 
number of carbon atoms. This is because of increase in van der Waals 
forces with increase in surface area.  
• In alcohols, the boiling points decrease with increase of branching in 
carbon chain. This is because of decrease in van der Waals forces with 
decrease in surface area. 
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b. Solubility:  
• Solubility of alcohols and phenols are soluble in water due to their ability 
to form hydrogen bonds with water molecules. 
 
• The solubility of alcohols decreases with increase in size of alkyl/aryl 
(hydrophobic) groups.  
 
5. Chemical properties of alcohols: 
a. Reactions involving cleavage of O–H bond: Alcohols react as  
nucleophiles: 
b. Reactions involving cleavage of carbon – oxygen (C–O) bond in 
Alcohols: Protonated alcohols react as electrophiles: 
c. Dehydration 
d. Oxidation 
6. Reactions of alcohols and phenols involving cleavage of O–H bond: 
a. Reaction with metals: 
 
 
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Class XII: Chemistry 
Chapter 11: Alcohols, Phenols And Ethers 
Top Concepts 
1. Structure of alcohols, phenols and ethers:  
  
2.  Preparation of alcohols: 
  
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 2
3. Preparation of phenols: 
               
4. Physical properties of alcohols and phenols: 
a. Boiling points:  
• Boiling points of alcohols and phenols are higher in comparison to other 
classes of compounds, namely hydrocarbons, ethers, haloalkanes and 
haloarenes of comparable molecular masses. This is because the –OH 
group in alcohols and phenols is involved in intermolecular hydrogen 
bonding. 
 
• The boiling points of alcohols and phenols increase with increase in the 
number of carbon atoms. This is because of increase in van der Waals 
forces with increase in surface area.  
• In alcohols, the boiling points decrease with increase of branching in 
carbon chain. This is because of decrease in van der Waals forces with 
decrease in surface area. 
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b. Solubility:  
• Solubility of alcohols and phenols are soluble in water due to their ability 
to form hydrogen bonds with water molecules. 
 
• The solubility of alcohols decreases with increase in size of alkyl/aryl 
(hydrophobic) groups.  
 
5. Chemical properties of alcohols: 
a. Reactions involving cleavage of O–H bond: Alcohols react as  
nucleophiles: 
b. Reactions involving cleavage of carbon – oxygen (C–O) bond in 
Alcohols: Protonated alcohols react as electrophiles: 
c. Dehydration 
d. Oxidation 
6. Reactions of alcohols and phenols involving cleavage of O–H bond: 
a. Reaction with metals: 
 
 
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b. Esterification: 
 
7. Reactions of alcohols involving cleavage of carbon – oxygen (C–O) 
bond: 
a. Reaction with hydrogen halides: 
conc.HCl ZnCl
2
Lucas reagent 2
ROH + HX  RX + H O
+
??? ???? ? ? 
b. Reaction with phosphorus trihalides: 
3 ROH + PX
3
 ? 3 R-X + H
3
PO
3
 (X = Cl, Br) 
c. Dehydration: 
 
d. Oxidation: 
Cu,573K
or
CrO
3
or
PCC
Cu,573K
or
CrO
3
Cu,573K
or
KMnO
4
Acidified potassium permanganate
Primaryalcohol Aldehyde
Secondary alcohol Ketone
Tertiaryalcohol Alkene
Alcohol Carboxylic acid
???? ? ?
?? ? ? ? ?
?? ? ? ? ?
?? ?? ?? ?? ??? ?? ? ?
 
   
 
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 1
Class XII: Chemistry 
Chapter 11: Alcohols, Phenols And Ethers 
Top Concepts 
1. Structure of alcohols, phenols and ethers:  
  
2.  Preparation of alcohols: 
  
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 2
3. Preparation of phenols: 
               
4. Physical properties of alcohols and phenols: 
a. Boiling points:  
• Boiling points of alcohols and phenols are higher in comparison to other 
classes of compounds, namely hydrocarbons, ethers, haloalkanes and 
haloarenes of comparable molecular masses. This is because the –OH 
group in alcohols and phenols is involved in intermolecular hydrogen 
bonding. 
 
• The boiling points of alcohols and phenols increase with increase in the 
number of carbon atoms. This is because of increase in van der Waals 
forces with increase in surface area.  
• In alcohols, the boiling points decrease with increase of branching in 
carbon chain. This is because of decrease in van der Waals forces with 
decrease in surface area. 
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 3
b. Solubility:  
• Solubility of alcohols and phenols are soluble in water due to their ability 
to form hydrogen bonds with water molecules. 
 
• The solubility of alcohols decreases with increase in size of alkyl/aryl 
(hydrophobic) groups.  
 
5. Chemical properties of alcohols: 
a. Reactions involving cleavage of O–H bond: Alcohols react as  
nucleophiles: 
b. Reactions involving cleavage of carbon – oxygen (C–O) bond in 
Alcohols: Protonated alcohols react as electrophiles: 
c. Dehydration 
d. Oxidation 
6. Reactions of alcohols and phenols involving cleavage of O–H bond: 
a. Reaction with metals: 
 
 
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b. Esterification: 
 
7. Reactions of alcohols involving cleavage of carbon – oxygen (C–O) 
bond: 
a. Reaction with hydrogen halides: 
conc.HCl ZnCl
2
Lucas reagent 2
ROH + HX  RX + H O
+
??? ???? ? ? 
b. Reaction with phosphorus trihalides: 
3 ROH + PX
3
 ? 3 R-X + H
3
PO
3
 (X = Cl, Br) 
c. Dehydration: 
 
d. Oxidation: 
Cu,573K
or
CrO
3
or
PCC
Cu,573K
or
CrO
3
Cu,573K
or
KMnO
4
Acidified potassium permanganate
Primaryalcohol Aldehyde
Secondary alcohol Ketone
Tertiaryalcohol Alkene
Alcohol Carboxylic acid
???? ? ?
?? ? ? ? ?
?? ? ? ? ?
?? ?? ?? ?? ??? ?? ? ?
 
   
 
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 5
8. Chemical properties of phenols: 
 
 
9. Acidic nature: 
a.  Phenol > H
2
O > Primary alcohol > Secondary alcohol > Tertiary 
alcohol  
 The acidic character of alcohols is due to the polar nature of O–H bond.  
                          
 Alkyl group is an electron-releasing group (–CH
3
, –C
2
H
5
) or it has electron 
releasing inductive effect (+I effect). 
 Due to +I effect of alkyl groups, the electron density on oxygen increases. 
 This decreases the polarity of O-H bond.  
 And hence the acid strength decreases. 
 
b.  Phenol is more acidic than alcohol because: 
 
• In phenol, the hydroxyl group is directly attached to the sp
2
 hybridised 
carbon of benzene ring which acts as an electron withdrawing group. 
Whereas in alcohols, the hydroxyl group is attached to the alkyl group 
which have electron releasing inductive effect. 
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