JEE Main levelOne or more correct optionsDifficulty 2 of 3bm098
Which statements about the peptide bond in proteins are correct?
AThe atoms C, O, N, H and the two attached alpha-carbons lie nearly in one plane.
BThere is free rotation about the C-N bond.
CThe C-N bond has partial double-bond character.
DThe cis arrangement about the C-N bond is generally preferred.
Answer: A, C
Resonance gives the C-N bond partial double-bond character, so rotation is restricted and the amide group is planar. The trans arrangement is generally preferred because it places the bulky alpha-carbon substituents far apart.