Collect. Czech. Chem. Commun. 2001, 66, 897-911

Nonlinear Hammett Relationships in the Reaction of Peroxomonosulfate Anion (HOOSO3-) with meta- and para-Substituted Anilines in Alkaline Medium

Subbiah Meenakshisundaram* and Ramanathan Sockalingam

Department of Chemistry, Annamalai University, Annamalainagar-608 002, India


The HOOSO3- oxidation of eleven meta- and para-substituted anilines to the corresponding nitrosobenzenes at pH ≈ 11 was characterized by the rate equation v = kK[OX][An]/(1 + K[An]). Formation constant of the reactive intermediate and its rate of decomposition were evaluated separately for ascertaining the structure-reactivity relationships. Under the experimental conditions the dianion, -O-O-SO3- is probably the effective electrophile. Kinetic data can be rationalized by a bimolecular process which involves the attack of nucleophilic nitrogen atom on the peroxidic oxygen. The highlight of the study is the opposite curvatures observed in the nonlinear Hammett plots of first-order rate constant k and the "equilibrium" constant K, being concave downward and upward, respectively.

Keywords: Nonlinear Hammett plot; Aniline; Peroxomonosulfate; Oxidations; Amines; Nitroso compounds; Substituent effects; Solvent effects.

References: 29 live references.