Linear Free Energy Relationships in SNAr Reactions of Aryl and Diaryl N-Anions with Aryl Halides
摘要:
A good correlation has been established between the Bronsted coefficients beta(Nuc) and beta(ox) for reactions of aryl-containing N-anions with various aryl halides. This correlation reflects the dependence of the internal barrier of aromatic nucleophilic substitution on the oxidation potentials of nucleophiles.
Rate constants of reactions between sodium salts of diarylamines N-anions and hexafluorobenzene and pentafluoropyridine in DMSO at 25 degreesC were determined. The Bronsted factors for substrates under consideration are 0.14 and 0.34 respectively. These data evidence a considerable effect of substrate electrophilicity on the reactivity of diarylamines N-anions in the SNAr reactions. Deviations of the Bronsted plot from linearity for the reactions of hexafluorobenzene with aryl-and diarylamines N-anions may be due to the difference in internal barriers of these reactions.