The electron localization function signature of the amide bond exhibits nitrogen lone pair character

An electron localization function (ELF) study of the amide bond at the: B3LYP/6-31+G(d,p)//MP2(FC)/6-31+G(d,p) level shows that the ELF isosurfaces near nitrogen resemble those found in planar ammonia where the lone pair is of necessity localized on the nitrogen atom. This suggests that in the planar form the neutral resonance structure is of considerable importance and gives rise to a characteristic ELF signature for nitrogen in the amide bond and similar settings where the nitrogen lone pair contributes to the bonding.