Electron-Density Relaxation and Oppositely Signed Reaction Constants in Dual Substituent Parameter Relationships in Dediazoniation Reactions

Why are there so few exceptions to the fact that ρR/ρF = λ is positive? A straightforward theoretical basis is provided for the interpretation of the dediazoniation of benzenediazonium ions, one of the most prominent examples of the few reactions for which the reaction constants ρR and ρF [Eq. (1)] have opposite signs. The results support the model that describes C-N bonding as synergistic N → C σ dative and C → N π backdative bonding. The analysis furnishes details about the electronic structure that cannot be deduced from physical-organic studies alone.