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: B3L YP/6-31+G(d,p)//MP2(FC)/6-31+G(d,p) level shows that the ELF isosurfaces ne ar nitrogen resemble those found in planar ammonia where the lone pair is o f necessity localized on the nitrogen atom. This suggests that in the plana r form the neutral resonance structure is of considerable importance and gi ves rise to a characteristic ELF signature for nitrogen in the amide bond a nd similar settings where the nitrogen lone pair contributes to the bonding .