Reduction of a carboxylic acid with lithium aluminium hydride gives

  • A. an aldehyde only
  • B. a primary alcohol
  • C. a ketone
  • D. an alkane

Explanation

Lithium aluminium hydride is powerful enough to reduce the carboxyl group all the way to a primary alcohol, passing through the aldehyde without stopping there. Milder reducing agents such as sodium borohydride will not touch a carboxylic acid at all, which is why the choice of reagent matters. The reaction must be carried out in dry ether, since the reagent reacts violently with water.

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