Why do we not see rotation in the peptide bond between the carbonyl carbon and

[Nadina]

amide nitrogen? Why do we not see rotation in the peptide bond between the carbonyl carbon and amide nitrogen?

a)Because it is a double bond
b)Because it is a single bond
c)Because of bond resonance
d)Because it is a covalent bond
e)Because of hydrogen bonding

[Kunal Pandya]

c)Because of bond resonance

[cspeptide]

Resonance is the reason why:
Peptide bonds are really made up of 2 resonance contributing structures
1) O=C-N
2) O-C=N
(both Cs are attached to C(alpha))

Just think of it as both bonds having a partial double bond properties.
If you built the models using double bonds you would notice that the whole structure would be planar at that bond and would not allow for rotation due to overlapping orbitals.