The SRN1 Reaction: An Attempt to Calculate the Thermodynamic Driving Force for the Addition of Nucleophiles to Phenyl Radical.
作者:Carlo Galli、Patrizia Gentili、Lian Zhang、Björn Åkermark、John H. Wagenknecht、George W. Francis、József Szúnyog、Bengt Långström
DOI:10.3891/acta.chem.scand.52-0067
日期:——
Phenyl radical is formed in the propagation chain of the aromatic SRN 1 reaction from cleavage of the radical anion of the precursor phenyl halide (PhX.-); subsequent addition of nucleophile Y- to Ph-. yields the radical anion of the substitution product (PhY.-). In this addition step, transfer of an electron from the nucleophile to Ph-. is concerted with bond formation, and the extra electron of the new two-center three-electron bond is, in general, located in a pi* MO of the aromatic moiety. Three factors mainly affect the efficiency of this addition step: (i) the energy of the new Ph-Y bond; (ii) the stability of the radical anion of the substitution product; (iii) the oxidation potential of the nucleophile. In keeping with these points, the energy of some Ph-Y bonds has been calculated, and the oxidation potential of Y- species, along with the reduction potential of the related PhY substitution products, have been determined. Calculation of the thermodynamic driving force of the nucleophile/radical addition step is reported for some significant nucleophiles. Finally, comparison of the thermodynamic driving force with experimental reactivity of the same nucleophile in the addition step is attempted.