Which one of the following statements is not correct about benzene?

Benzene (C₆H₆) is an aromatic hydrocarbon consisting of six carbon atoms arranged in a hexagonal ring, with alternating single and double bonds that are delocalized. This delocalization gives benzene its characteristic resonance stability. Every carbon atom in benzene is sp² hybridized, forming three sigma bonds—two with neighboring carbons and one with hydrogen.

The bond lengths in benzene are equal, about 1.39 Å, which is intermediate between a single (1.54 Å) and a double bond (1.34 Å). Therefore, the statement that the C–H bond length is 1.09 Å is incorrect when referring to the carbon–carbon bonds in benzene. The C–H bond length is indeed 1.09 Å, but the question refers to the internal structure, so the incorrectness arises from misunderstanding benzene’s uniform C–C bond structure.

When benzene undergoes hydrogenation, it converts to cyclohexane, releasing about 208 kJ/mol of energy, confirming that this value is correct. Benzene’s resonance energy is approximately 150.5 kcal/mol, which reflects its extraordinary stability compared to hypothetical localized structures. The molecular mass of benzene, 78.108 g/mol, is also accurate and derived from its atomic composition (6 carbon and 6 hydrogen atoms).

The delocalized π-electrons above and below the ring plane contribute to benzene’s chemical inertness and unique aromatic behavior. Its resonance model explains why benzene resists addition reactions typical of alkenes and instead undergoes substitution reactions that preserve the aromatic ring.

Understanding these properties helps students grasp why benzene is a cornerstone of organic chemistry. It exemplifies aromatic stability, resonance energy, and bond uniformity, essential for studying aromatic compounds and reaction mechanism