CHEM 130 Lecture Notes - Lecture 12: Amide, Carbon-13 Nuclear Magnetic Resonance, Electron Diffraction
Document Summary
The amide is a very important group in nature since it is the link by which amino acids join together to form peptides, which make up the proteins in our bodies. The structure of this deceptively simple group has an unexpected feature, which is responsible for much of the stability of proteins. In the allyl anion, carboxylate, and nitro systems we had four electrons in the system spread out over three atoms. The nitrogen in the amide group also has a pair of electrons that could conjugate with the bond of the carbonyl group. Again, for effective overlap with the bond, the lone pair of electrons must be in a p orbital. This in turn means that the nitrogen must be sp2 hybridized. In the carboxylate ion, a negative charge was shared (equally) between two oxygen atoms. In an amide there is no charge as such the lone pair on nitrogen is shared between the nitrogen and the oxygen.
