`- overset(overset(O)(||))C-NH-("peptide bond").` Which statement is incorrect about peptide bond?

Options

A. C - N bond length in proteins is longer than usual bond length of N - C bond
B. Spectroscopic analysis show planar structure of `- underset(underset(O)(||))C-NH-("group")`
C. C - N bond length in proteins is smaller than usual bond length of C - N bond
D. None of these

Answer

To determine which statement is incorrect about the peptide bond, we will analyze each statement step by step.

### Step 1: Analyze the first statement
The first statement claims that the CN bond length in proteins is longer than the usual CN bond length.

- **Peptide Bond Structure**: A peptide bond is formed between the carboxyl group of one amino acid and the amino group of another, resulting in a CN bond.
- **Resonance**: In peptide bonds, the nitrogen lone pairs can participate in resonance, forming a partial double bond character with the carbonyl carbon. This resonance leads to a shorter bond length than a typical single CN bond.
- **Conclusion**: Therefore, the first statement is incorrect because the CN bond length in peptide bonds is shorter, not longer.

### Step 2: Analyze the second statement
The second statement mentions that spectroscopic analysis gives us the planar structure of peptide linkage.

- **Spectroscopy**: Spectroscopy involves studying the interaction of matter with electromagnetic radiation, which helps determine molecular structures.
- **Planarity of Peptide Bonds**: The presence of partial double bond character due to resonance in peptide bonds results in a planar structure. This is consistent with sp² hybridization, which also supports the planar geometry.
- **Conclusion**: This statement is correct.

### Final Conclusion
After analyzing both statements, we conclude that the first statement is incorrect regarding peptide bonds, while the second statement is correct.