Amino Acid Structure and Properties

Properties of the amide bond

An amide bond in the context of connecting two amino acids can also be called a peptide bond. It has three important properties

  1. Does not allow free rotation about the C-N bond

    While the C-N bond of an amide is usually drawn as a single bond, it really is not in this case. There is "some double bond character" to it as shown to the left. One can think of the amide bond as somewhere in between these two pictures or as rapidly flipping from one to the other.

  2. Is almost always found in the "trans" configuration

    Since there is no rotation then the relative "placement" of the H and the O atoms is fixed. They are almost always found facing away from each other in a "trans" configuration.

  3. The bond overall is polar

    Just as in water the oxygen atom represents a more negatively charged side of the group while the H side of the group is more positively charged thus there is a polar moment to the entire functional group.



 
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