Which among the following groups is not reduced by BH₃

Concept:

• Reduction by Borane (BH₃): Borane (BH₃) is a selective reducing agent used in organic synthesis.

  • alkene: Borane reduces alkenes through hydroboration, adding across the double bond to form organoborane intermediates.

  • -NO₂ (Nitro group): The nitro group is generally resistant to reduction by borane under normal conditions.

  • -COOH (Carboxylic acid): Carboxylic acids can be reduced by borane to form primary alcohols.

  • acetic anhydride: Borane can reduce anhydrides to alcohols or aldehydes.

Explanation:

• 

  • Borane reduces alkenes through hydroboration, forming organoboranes.

• -NO₂:

  • The nitro group is generally resistant to reduction by borane.

• -COOH:

  • Borane reduces carboxylic acids to primary alcohols.

• 

  • Borane can reduce anhydride to alcohols or aldehydes.

Conclusion:

The group that is not reduced by BH₃ is: -NO₂