Amide functional group atomic orbital structure

Furthermore, the oxygen atom of the carbonyl group in the amide function has an electron pair oriented antiperiplanar to the polar C-N bond there is therefore an electronic delocalization caused by the overlap of that oxygen electron pair orbital with the antibonding orbital of the C-N sigma bond (o ) as shown in two dimensions by structure 5 and in three dimensions by structure . This additional n-o delocalization is referred to here as a secondary electronic delocalization. Thus, amides are similar to esters because they both have the primary electronic effect and one secondary electronic effect. This is in contrast with Z esters which have two secondary electronic effects besides the primary electronic effect. 

The C—O double bond is the most important functional group in organic chemistry. It is present in aldehydes, ketones, acids, esters, amides, and so on. We shall spend Chapters 5-10 discussing its chemistry so it is important that you understand its electronic structure. As in alkenes, the two atoms that make up this double bond are sp2 hybridized. The carbon atom uses all three sp2 orbitals for overlap with other orbitals to form o bonds, blit the oxygen uses only one for overlap with another orbital (the sp2 orbitals on the carbon atom) to form a O bond. However, the other two sp2 orbitals are not vacant—they contain the oxygen s two lone pairs. A p orbital from the carbon and one from the oxygen make up the n bond which also contains two electrons. 

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