Peroxomonophosphoric Acid Oxidation. 7. Studies of the Kinetics and Substituent Effect in the Oxidation of Aniline

Article abstract of DOI:10.1021/jo00333a013

The kinetics of the oxidation of aniline and 12 substituted anilines by peroxomonophosphoric acid (PMPA) have been measured.The reactions are first order in PMPA and first order in amine.The rate laws are given in eq 10 and 13.The unprotonated amine is the reactive species.Correlation of log rates with ?, ?⁺, ?^-, and ΔpK_a yielded values of ρ (-1.37), ρ⁺ (-1.31); ρ^- (-1.38), and β (0.58), respectively.The values suggest an electron-deficient reaction center, and the Bronsted coefficient, β, indicates considerable bond formation in the transition state.All the ortho substituents provide steric retardation for the formation of the transition state.Oxidation of aniline gives azobenzene, azoxybenzene, p-aminophenol, and p-benzoquinone routed through the reactive intermediate phenylhydroxylamine.The individual reactivities of various ionized PMPA species with the amine have been estimated.