Aldehydes and ketones

• Both aldehydes and ketones can be reduced forming primary and secondary alcohols respectively
• Reduction of aldehydes and ketones with NaBH4

  NaBH4 is sodium borohydride

  • It's mechanism is nucleophilic addition with the nucleophile being H- (hydride ion)
  • In acidic conditions
  • E.g. CH3CH2CHO + 2 [H] --> CH3CH2CH2OH which is proponal --> propan-1-ol
  • [H] is the reducing agent
• In the reduction of an asymmetrical ketone, a chiral center would be produced resulting in a racemic mixture of optical isomers because there's equal chance of either side of the carbon (double bond ) being attacked due to planar nature of carbonyl
• In nucleophilic additions with cyanide ions , KCN is used instead of HCN because it's very volatile and highly toxic liquid while KCN is a stable solid
• Due to C=O being planar, there's an equal chance of it being attacked from either side which results in a racemic mixture that would be optically inactive