Reduction Reactions (HL)

Just as you can oxidise alcohols to form compounds with a carbonyl group, you can then reduce carbonyl containing compounds back to alcohols.

Reagents for reduction

  • Lithium aluminium hydride                 LiAlH4
  • Sodium borohydride                             NaBH4

Lithium aluminium hydride

Sodium borohydride

 

Structures of the reducing agents

 

 

Read through your text and annotate your notes find the answers to the questions below.

✍️  What difference is there in the conditions under which the two reagents might be used?
✍️   Which reagent is preferred from the reduction of carboxylic acids and why?

Reduction of Carbonyl Containing Compounds

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✍️  For the following starting materials, draw the structures and name to products formed when treated with lithium aluminium hydride.

  • propanoic acid
  • butanone

Conversion of nitrobenzene to phenylamine

This reduction happens via a two step process as summarised below.

✍️   After reading your text or other sources, elaborate on what is happening in both stages in your notes.  Make sure you can answer these questions.

  • Why is a protonated phenylammonium ion produced in the first step?
  • What technique is used to heat the reaction?
  • What is the role of the tin?
  • What is the purpose of using sodium hydroxide in the second stage?

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