Reduction of Aldehydes and Ketones

Reduction of Aldehydes and Ketones to Alcohols

Aldehydes and ketones are reduced to primary and secondary alcohols respectively. Any one of the following reducing agents can be used for this purpose.

  1. H2 in the presence of Ni, Pt or Pd.
  2. Lithium aluminium hydride (LiAlH4).
  3. Sodium borohydride (NaBH4).
Reduction of Aldehydes to alcohols
Reduction of Ketones to alcohols

Convert propanone to propene.

Reduction of Aldehydes and Ketones to Hydrocarbons

The carbonyl group in aldehydes and ketones can be reduced to −CH2 group to form hydrocarbons.

Reduction of the carbonyl group

Zinc amalgam (Zn-Hg) and conc. HCl are used for reduction of aldehydes and ketones to hydrocarbons. Reduction of aldehydes and ketones by this method is known as Clemmensen reduction.

Reduction of Aldehydes to Hydrocarbons | Clemmensen reduction
Reduction of Ketones to Hydrocarbons | Clemmensen reduction

Alternatively, the carbonyl group can be reduced to hydrocarbon using hydrazine (NH2−NH2) followed by heating with sodium or potassium hydroxide in high boiling solvent such as ethylene glycol. Reduction by this method is known as Wolff-Kishner reduction.

Wolff-Kishner reduction