Electron Delocalization, Resonance and Bond Length Alternation

Electron delocalization, resonance and bond length alternation 

The very concept of resonance originated in VB theory and was extensively exploited in qualitative explanations of stability and other properties of tt-electron systems [78], surviving vitriolic attacks by some Soviet philosophers of the time. Recent re-examination of these ideas [61,65,79-82], based on new semiempirical and ab initio results, shows that the concept of resonance or 7r-electron delocalization is very subtle and prone to misinterpretation when improperly isolated. 

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