Benzene: Resonance

Also called

benzene · resonance · resonance structures · Kekulé structure · aromatic compounds · aromaticity · delocalised electrons · pi electron cloud · C6H6 · bond length 139 pm · electrophilic substitution · bromination of benzene · resonance hybrid · Huckel rule · arenes · बेंज़ीन · अनुनाद · ऐरोमैटिक यौगिक

Topics

• Benzene, C₆H₆, is a flat hexagon of six carbons, each bonded to one hydrogen; every carbon is sp² hybridised.
• Kekulé drew two structures with alternating double bonds; the real molecule is a resonance hybrid of both.
• All six C–C bonds are the same length, 139 pm: between a single bond (154 pm) and a double bond (134 pm).
• Each carbon has one unhybridised p orbital; the six overlap sideways into a π cloud above and below the ring.
• The six π electrons are delocalised over all six carbons, not fixed between any two: this is the resonance.
• Delocalisation lowers the energy by about 150 kJ/mol (the resonance energy), so benzene is unusually stable.
• Benzene resists addition reactions, which would break the delocalised cloud; it undergoes substitution instead.
• In electrophilic substitution an electrophile such as Br⁺ or NO₂⁺ replaces one hydrogen and the ring stays aromatic.

About this model

A GLB file of about 217 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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