Amide resonance template

N-Methylacetamide: the N lone pair forms C=N⁺ as the C=O π bond moves onto oxygen, which explains the planar, slowly rotating amide (peptide) bond.

What the template shows

• The nitrogen lone pair gives the C–N bond partial double-bond character
• Resonance contributors
• Neutral form (major) ↔ charge-separated form
• The C–N bond (about 133 pm) is shorter than a C–N single bond (147 pm): it has partial double-bond character.
• Rotation about C–N is slow (barrier about 80 kJ mol⁻¹), so the amide unit is planar; in proteins this makes the peptide bond rigid.
• Amide nitrogen is not basic: its lone pair is delocalised onto oxygen, and amides protonate on O.
• Amides are the least reactive acid derivatives because this donation is the strongest (N is less electronegative than O).
• Contributors are not in equilibrium: the real species is one hybrid of them · every part of this figure is editable

Drawn with 10 atoms, 3 arrows, 2 shapes – every one editable in MolDraw.

Sources

• Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012, ch. 7 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook