Which of the following is not correct? (1) The bond angle in...

Which of the following is not correct?
(1) The bond angle in benzenc is $120^{\circ}$
(2) The $\mathrm{C} \mathrm{C}$ bond length in benzene is $1.39 \AA$
(3) Benzene was discovered by Raraday
(4) Benzene is an unsaturated hydrocarbon and participate in addition reactions casily

Key Concepts

Aromaticity

Aromaticity is a fundamental concept in organic chemistry that describes the enhanced stability of cyclic, planar molecules with a delocalized ?-electron system. Benzene is the classic example of an aromatic compound, where the electrons are shared evenly over the ring, giving rise to unique structural and reactivity characteristics that distinguish it from typical unsaturated compounds.

Molecular Structure of Benzene

The molecular structure of benzene consists of a hexagonal ring with sp²-hybridized carbon atoms, leading to uniform bond angles of 120°. This structure results in identical carbon–carbon bond lengths due to the delocalization of electrons, which creates a resonance hybrid that contributes to benzene’s stability.

Chemical Reactivity of Aromatic Compounds

Due to its aromatic stabilization, benzene resists reactions that would disrupt its delocalized electron system. Instead of readily undergoing addition reactions typical of many unsaturated hydrocarbons, benzene preferentially undergoes substitution reactions that preserve its aromatic character.

Unsaturation in Hydrocarbons

Unsaturation refers to the presence of double or triple bonds in hydrocarbons, which typically makes them reactive towards addition reactions. However, in aromatic compounds like benzene, the unsaturation is arranged in a cyclic, conjugated system that bestows significant stability and alters their expected reactivity compared to other unsaturated hydrocarbons.

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