Reaction of Carboxylic Acid and Derivations

• Carboxylic acid derivatives undergo various types of reactions

  • acyl group substitution
  • reduction
  • reactions with organometallic reagents
• acyl group substitution

  • Nucleophiles attack the carboxylic acid derivatives from one side of the carbonyl carbon thereby converting it to tetrahedral geometry.
  • The X group serves as the leaving group and when it leaves, the carbon reforms double bond with oxygen.
  • At the end of reaction, nucleophile becomes the new X group.
• acyl group substitution

  • The order of reactivity of various carboxylic acid derivatives is as follows:

  acyl phosphate → thioester → ester=carboxylic acid → amide →

  carboxylate

  • Acyl phosphate is the most reactive and carboxylate is the least reactive.
  • This difference in reactivity is due to the basicity of leaving group as weaker bases are better leaving groups.
• reduction

  • Carboxylic acid derivatives are reduced to either aldehydes or alcohols.
  • Reduction reactions include catalytic dehydrogenation, complex metal hydride reactions, diborane reduction etc.
  • For example, acyl halides are reduced to aldehyde in the presence of palladium as catalyst under mild conditions as shown in the reaction below.
• reactions with organometallic reagents

  • Carboxylic acid derivatives including esters, anhydrides and acyl chlorides react with organometallic compounds to form alcohol products.
  • For example, esters react with Grignard reagents to form tertiary alcohols.