Preparation of Alcohols ^{(iii)
from Haloalkanes, Aldehydes and Ketones}

From haloalkanes

Haloalkanes are heated with aqueous sodium or potassium hydroxide to form alcohols.

From aldehydes and ketones

By reduction

Aldehydes and ketones are reduced to corresponding alcohols in a number of ways like :

• Addition of H₂ in the presence of catalyst like platinum, nickel.
  
• By complex metal hydrides such as Lithium aluminium hydride (LiAlH₄) or sodium boro hydride (NaBH₄)
  

By addition of Grignard reagents

Grignard reagents (R−MgX) are polar in nature where carbon is electronegative and Mg is electropositive. Due to the polar nature of Grignard reagents, they react with aldehydes and ketones to form addition products which upon decomposition gives alcohols with water or dil. H₂SO₄.

Important points regarding this reaction

• When formaldehyde (HCHO) is used in the above reaction, primary alcohol is obtained.
  
• When aldehydes other than formaldehydes are used, secondary alcohols are obtained.
  
• When ketones are used, tertiary alcohols are obtained.
  

Questions