The rearrangement of aromatic nitro compounds. Part 1. The reactions of nitroanilines in aqueous sulphuric acid

Abstract

A number of substituted 2-nitroanilines rearrange in concentrated sulphuric acid at 110 °C to yield products that appear to be derived from 1,3-migration of the 2-nitro-group. For 2,3-dinitroaniline, the rate of reaction is almost independent of acidity over the range 83–97% sulphuric acid and the solvent isotope effect k(H₂SO₄)/k(D₂SO₄) is 1.3–1.9. Methyl and t-butyl groups, when present as additional substituents in 2,3-dinitroaniline, have only a small effect on the reaction rate but 3-methyl-2-nitroaniline reacts much more slowly than 2,3-dinitroaniline. These results are discussed in terms of a rate-determining migration of the 2-nitro group following protonation at the 2-position.