Studies of tertiary amine oxides. Part 7. Solvent effects on the rearrangement of N-arylamine oxides to O-arylhydroxylamines. The SNi mechanism

Abstract

The rate of rearrangement of N-arylamine oxides (4) to O-arylhydroxylamines (5) was measured in different solvents. The rate of isomerisation of p-nitrophenyl N-oxides correlates with the dielectric constants of aprotic solvents and with the hydrogen-bonding ability of protic solvents. The rearrangement of o-nitrophenyl N-oxides shows much less variation in rate with solvent polarity. All kinetic results are explained in terms of an intramolecular cyclic mechanism (S_Ni).