AQA A Level Chemistry

Revision Notes

7.2.2 Reduction of Carbonyls

Reduction of Carbonyls

Reduction of Carbonyls

  • There are a large number of reducing agents which will reduce both an aldehyde and a ketone to an alcohol
  • Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohols
  • Possibly the most common reducing agent for this is sodium tetrahydridoborate, NaBH4
    • You may also see this named as sodium borohydride in some sources
  • In an aqueous solution, NaBH4 generates the hydride ion nucleophile, :H
  • The hydride ion will reduce a carbonyl group in an aldehyde or a ketone, but is not strong enough to reduce a C=C double bond
    • This is because it is attracted to the C in the C=O bond, but is repelled by the high electron density of the C=C bond
  • When this reaction takes place, it is an example of a nucleophilic addition reaction

Reduction Reactions

  • Carboxylic acid to a primary alcohol:downloadable AS & A Level Chemistry revision notes
  • Aldehyde to a primary alcohol:downloadable AS & A Level Chemistry revision notes
  • Ketone to a secondary alcohol:

 

 

Exam Tip

Lithium tetrahydridoaluminate, LiAlH4, in a non-aqueous solvent can also be used as a reducing agent for the reduction of carbonyls.

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