Q.Benzene has, equivalent six carbon atoms and six hydrogen atoms. Justify.
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Start your 14-day free trial to unlock the full solution →Benzene's six carbons (and hydrogens) are proven equivalent because only a single monosubstituted product ever forms, consistent with the pi electrons being delocalised equally around the ring.
Benzene (C6H6) is represented as a hexagonal ring with alternating single and double bonds (Kekule structure), which would suggest two 'kinds' of C-C bonds (single, longer, and double, shorter) and, in principle, non-equivalent carbon/hydrogen positions. However, benzene actually behaves as a resonance hybrid of two (or more) Kekule structures, with the six pi electrons delocalised uniformly over all six carbon atoms rather than being fixed in three localised double bonds. As a direct experimental consequence:
- All six C-C bond lengths in benzene are found (by X-ray diffraction) to be equal, ~139 pm - intermediate between a pure single bond (154 pm) and a pure double bond (134 pm).
- When benzene undergoes a substitution reaction (e.g., bromination), replacing any one of its six hydrogens gives exactly ONE monosubstituted product (e.g., only one bromobenzene), regardless of which position is substituted, since all six positions are indistinguishable. …
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