Question

What is a major consequence of the partial double bond character ?

Answer 1

1. Partial double bond characters have the bond order between 1 and 2. Bond order is the number of bonding pair electrons present between two atoms.
2. Due to resonance, Nitrogen donates its lone pair of electrons to the carbonyl carbon and tends the electrons from the carbonyl double bond to the Oxygen, forming a negative charge at anion.
3. Because of resonance, a more stable resonance structure is that which contains Oxygen as an anion. Due to which the bond length between $\mathrm{C}-\mathrm{N}$ decreases.
4. Due to this double bond character the stability increases and the rotation around the double bond is restricted. Due to the partial bond character Amides being planar makes us to assume them cis as well as trans conformation.
5. In the cis configuration, the two alpha carbon atoms are present on the side of the peptide bond.
6. In the trans configuration, two alpha carbons present on opposite side.
7. This is a major consequence of the partial double bond character in amides.