Aromatic nucleophilic substitution reactions of ambident nucleophiles. III. Reactivity of the nitrite ion

Abstract

The reactivity patterns in the SNAr reactions of the ambident nitrite ion with nitrohalobenzenes depend on the solvent, the leaving group, and the position of substituents. The rate-determining step can be either the formation or decomposition of the intermediate complex, depending on the leaving group and mode of attack by the nitrite ion. The activating effect of a para relative to the same ortho substituent depends on the leaving group and on whether nitrite is attacking via its nitrogen or oxygen atom. The nitrite ion is of comparable nucleophilicity to azide ion, but is a much weaker carbon base than azide when attacking through its nitrogen atom, although it is a strong carbon base when attacking through oxygen. The reactivity patterns of nitrite ion in SNAr reactions are compared with those of other nuclephiles, such as N3-, SCN-, the halides, RS- and RO-