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 Chapter 20: Carboxylic Acid Derivatives. Nucleophilic Acyl Substitution 
Ch 20 contents

Structure of Carboxylic Acid Derivatives

carboxylic acid
aldehyde
alkene
resonance in carboxylic acid derivatives
  • It also has implications for structure... Look at the JMOL image of the amide to the right. 

QUESTION What do you notice about the geometry at the N atom ? ANSWER

  • Amines and ammonia are usually pyramidal (want to see ?)
  • The planar sp2 N system allows the N lone pair to align with the C=O π system (see image below, with the other bonds omitted for clarity)
  • The resonance interaction in the amide results in the C-N bond having some double bond character (shorter, restricted rotation)
orbital picture of amide resonance
amide

 
 
 
 
  • Nitriles are slightly different to the other derivatives in that they involved a triple bond.
  • Nitriles consists of a N atom bonded to a C atom via a triple bond in a linear, sp hybridisation model similar to that of an alkyne. Compare the JMOL images to the right.
 
nitrile
alkyne

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Dr. Ian Hunt, Department of Chemistry, University of Calgary