Physical & Chemical Properties of Alcohols

0
106
chemistry 12th class cbse notes

Physical properties of alcohols

  • Lower alcohols are liquid at room temperature while higher ones are solid.
  • The boiling point of alcohols is higher than haloalkanes with the same number of carbon atoms. This is due to the fact that alcohols are associated via intermolecular hydrogen bonding. For the same alcohol, as the branching increases, boiling point decreases due to decrease in surface area.
  • Solubility in water decreases with increase in molecular mass due to a decrease in the extent of intermolecular hydrogen bonding.
  • Alcohols are weaker acids than water due to the lower polarity of O – H bond in alcohols. The acidic strength of alcohols decreases as the number of electron donating groups increase at carbon.

Chemical Properties of alcohols

Reactions of alcohols involving cleavage of O-H bond

•    Reaction with metals:

Reactions of alcohols involving cleavage of O-H bond

•    Reaction with carboxylic acid (Esterification):

Reactions of alcohols involving cleavage of O-H bond

•    Reaction with Grignard reagent:

Reactions of alcohols involving cleavage of O-H bond

Reactions involving cleavage of C – O bond

For the reaction involving cleavage of C – O bond, the reactivity order is

Reactions involving cleavage of C – O bond

•    Formation of halides:

Reactions involving cleavage of C – O bond

Oxidation of alcohols

Depending upon the structure of the alcohol and the type of oxidising agent used, oxidation of alcohol gives different products.

Oxidation of alcohols

Dehydrogenation of alcohols

Dehydration of alcohols takes place in acidic medium. Intra-molecular dehydration leads to the formation of alkene while inter molecular dehydration forms ether.

Order of ease of dehydration is: 3° > 2° > 1°

Dehydrogenation of alcohols

Dehydration of alcohols

Dehydration of alcohols with conc. H2SO4 at different temperatures yields different products.

Dehydration of alcohols

The ease of dehydration of three alcohols increases in the order

10 ROH < 20 ROH < 30 ROH

 

LEAVE A REPLY

Please enter your comment!
Please enter your name here