Regioselective reaction INDEX

The average local ionization energy /(r) is probably the most effective single reaction index for analyzing regioselectivity and relative reactivity of S Ar. The /(r) function was first proposed by Sjoberg et al. in 1990 [82] and is rigorously defined within the frameworks of Hartree-Fock theory and KS-DFT by (Eq. 4.9)... 

MO studies of aromatic nitration cast doubt on the existence of jt-complexes and electron-transfer complexes in liquid-phase nitrations.14 The enthalpy of protonation of aromatic substrates provides a very good index of substrate reactivity to nitration. Coulomb interaction between electrophile and substituent can be a special factor influencing regioselectivity. A detailed DFT study of the reaction of toluene with the nitronium ion has been reported.15 Calculated IR spectra for the Wheland intermediates suggest a classical SE2 mechanism. MO calculations of cationic localization energies for the interaction of monosubstituted benzenes with the nitronium ion correlate with observed product yields.16... 

Regioselectivity of polar DA reactions. The local electrophilicity index. 

Normally the polarity of the normal electron demand DA process has been studied by means of global electrophilicity index difference between reactants and the regioselectivity of the normal electron demand DA reaction using the local electrophilidty index for dienophiles (electrophiles in the reaction) and the local nudeophilicity index for dienes (nucleophiles in the reaction). 

DFT calculations of the electrophilicity and nucleophilicity indexes in general agree with the experimental results and they are a good reactivity and regioselectivity predictors in this type of polar cycloaddition reactions... 

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