Why is benzene extra ordinarily stable though it contains three double bonds?
Benzene is extraordinarily stable due to the resonance and delocalisation of its electrons. According to Valence Bond Theory, benzene is a hybrid of various resonating structures, mainly the two Kekulé structures.
The six electrons in benzene are delocalised and can move freely about the six carbon nuclei, instead of being localised between any two carbon atoms. This delocalised electron cloud is attracted more strongly by the nuclei of the carbon atoms than a localised electron cloud.
Additionally, X-ray diffraction data shows that all six C—C bond lengths are the same (139 pm), which is intermediate between a single and a double bond. The absence of pure double bonds and the presence of delocalised electrons make benzene more stable than the hypothetical cyclohexatriene.
Explanation
The textbook explains benzene's unusual stability through resonance and the delocalisation of its six pi electrons. Unlike localized double bonds, the delocalized electron cloud is more strongly attracted to the carbon nuclei, and the uniform C-C bond length (139 pm) confirms the absence of pure double bonds, making it more stable than a hypothetical cyclohexatriene.