BRAINCAKEEvidence for Delocalisation
Three main pieces of evidence show that benzene is not the Kekulé structure and support the delocalised model.
1. Bond lengths. X-ray diffraction shows that all six carbon-carbon bonds in benzene are the same length, 0.139 nm. This is between the length of a C-C single bond (0.154 nm) and a C=C double bond (0.134 nm), and the ring is a regular hexagon.
2. Enthalpy of hydrogenation. Cyclohexene has one C=C bond:
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Key terms in this lesson
- enthalpy of hydrogenation
- The enthalpy change when one mole of a compound reacts completely with hydrogen to saturate a carbon-carbon double bond, under standard conditions.
More in Arenes
- Benzene
- The Kekulé Model
- The Delocalised Model of Benzene
- Combustion of Benzene
- Electrophilic Substitution
- Bromination of Benzene
- Nitration of Benzene
- Friedel-Crafts Alkylation
All 13 lessons in Arenes · All Edexcel A-level Chemistry topics