Amides (OCR A Level Chemistry)

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Amides

  • Amides are formed from the condensation reaction of carboxylic acids or acyl chlorides with ammonia or amines
  • Amides are common in nature such as in proteins where the amine and carboxylic acid groups of amino acids bond together
  • Amides have a general structure of RCONR2

6-4-4-general-structure-of-an-amide

The general structure of an amide

  • Amides can be classified as primary, secondary or tertiary amides
  • Like amines, this is done as a comparison to ammonia, depending on the number of substitutions on the amide nitrogen 
    • Primary amide - one carbon bonded to the amide nitrogen 
      • R' and R'' are both hydrogen atoms so one "ammonia" hydrogen has been substituted with the carbonyl group from the RCO portion of the molecule
    • Secondary amide - two carbons bonded to the amide nitrogen (one MUST be the carbonyl carbon)
    • Tertiary amide - three carbons bonded to the amide nitrogen (one MUST be the carbonyl carbon)

Naming primary amides

  • For primary amides, we simply add -amide to the stem name
    • e.g. CH3CONH2
      • Contains two carbons with a C-C (ethan-) and an amide group (-amide)
      • This gives us ethanamide

Naming secondary amides

  • For secondary amides, the alkyl chain attached to the nitrogen is added at the start of the chemical name
  • This alkyl chain is prefixed with N-
  • The chain containing the carbonyl group is named the same as a primary amide
    • e.g. CH3CONH(C3H7)
      • Contains a propyl group on the nitrogen (N-propyl) 
      • Contains two carbons with a C-C (ethan-) and an amide group (-amide)
      • This gives us N-propylethanamide

Naming tertiary amides

  • For tertiary amides, there are two alkyl chains attached to the nitrogen
  • The naming of these chains is the same as secondary amides
  • As with standard nomenclature, these chains are listed in alphabetical order and the prefix 'di-' is used if necessary
    • e.g. CH3CONCH3(C3H7)
      • Contains a methyl group on the nitrogen (N-methyl)
      • Contains a propyl group on the nitrogen (N-propyl) 
      • Contains two carbons with a C-C (ethan-) and an amide group (-amide)
      • This gives us N-methyl-N-propylethanamide

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Sonny

Author: Sonny

Expertise: Chemistry

Sonny graduated from Imperial College London with a first-class degree in Biomedical Engineering. Turning from engineering to education, he has now been a science tutor working in the UK for several years. Sonny enjoys sharing his passion for science and producing engaging educational materials that help students reach their goals.