Kinetics and mechanism of peroxysulfate/NaNO2 mediated nitration of phenols in aqueous bisulfate medium

Abstract

Peroxy sulfates (PS) like peroxydisulfate (PDS), and peroxymosulfate (PMS) have been accomplished as an efficient reagents for KHSO4/NaNO2 mediated nitration of aromatic compounds (S) such as phenols in aqueous bisulfate and acetonitrile medium, under the conditions [NaNO2] ≫ [PS]. The kinetics of the reaction depicted first order dependence on [S], [NaNO2], and [PS]. Reaction rates were sensitive to the introduction of electron donating or withdrawing groups. However, our efforts to correlate the kinetic results into Hammett’s structure–reactivity equation were not fruitful. Observed deviations from the linearity of Hammett’s equation have been interpreted in terms of effective Hammett’s constants (σ ¯ or σeff), para resonance interaction energy (ΔΔGp) values and Yukawa–Tsuno’s resonance stabilization parameter (r). The observed negative magnitude of entropy of activation (∆S#) values suggests greater solvation and/or cyclic transition state before yielding products.