Point out the wrong statement in relation to the structure of benzene

Options

A. It forms only one monosubstitution product
B. The C-C bond distance in benzene is uniformly 1.397 Å
C. It is a resonance hybrid of a number of canonical forms
D. It has three delocalised `pi`-molecular orbitals

Answer

To identify the wrong statement in relation to the structure of benzene, we will analyze each statement provided in the question.

1. **Benzene forms only one mono-substitution product**: This statement is true. Benzene has symmetrical structure, and when it undergoes mono-substitution reactions, it yields only one product due to its symmetrical nature.

2. **The C-C bond length in benzene is uniformly 1.397 Å**: This statement is also true. In benzene, all carbon-carbon bonds are of equal length due to the delocalization of electrons, and the bond length is indeed approximately 1.397 Å.

3. **Benzene is a resonance hybrid of a number of canonical structures**: This statement is true. Benzene can be represented by multiple resonance structures, and its actual structure is a resonance hybrid of these structures.

4. **Resonance hybrids are real, while canonical structures are imaginary**: This statement is true. Resonance hybrids represent the actual structure of the molecule, while canonical structures are theoretical representations that help in understanding resonance.

5. **It has 3 delocalized pi molecular orbitals**: This statement is incorrect. Benzene has 6 π electrons that are delocalized over the ring, and it does not have just 3 delocalized π molecular orbitals. Instead, it has a single set of π molecular orbitals that are fully delocalized across all six carbon atoms.

### Conclusion:
The wrong statement in relation to the structure of benzene is: **"It has 3 delocalized pi molecular orbitals."**