ARYL-CONTAINING AND HETARYL-CONTAINING AMIDE ANIONS IN REACTIONS OF AROMATIC NUCLEOPHILIC-SUBSTITUTION

The results of kinetic studies of SNAr reactions of p-nitrohalobenzene s, hexafluorobenzene, and pentafluoropyridine with aryl-, diaryl-, and hetarylamide anions under homogeneous conditions (in dimethyl sulfoxi de) and under conditions of phase transfer catalysis (in toluene) are analyzed. The increase in the Bronsted coefficient beta(Nu) in reactio ns of amide anions in DMSO as the electrophilicity of the substrate in creases and steric hindrance in nucleophiles decreases may result from a higher degree of charge transfer from a nucleophile to a substrate in the transition state. The possibility of replacement of the SNAr by the SET mechanism in these reaction is discussed.