Reduction of an acid chloride to an aldehyde:

Borane (B₂H₆) can be employed as a reducing agent to transform carboxylic acids to primary alcohols. One benefit of using borane rather than LiAlH₄ is the fact that the former does not decrease any nitro groups that might be present. LiAlH₄ decreases a nitro group (NO₂) to an amino group (NH₂).

It is value noting that carboxylic acids and acid derivatives are not reduced through the milder reducing agent - sodium borohydride (NaBH₄). Hence this reagent can be employed to reduce aldehydes and ketones without influencing any carboxylic acids or acid derivatives which might be present.

Figure: Reduction of an acid chloride and an ester to an aldehyde.