Oxidation of Formamidines by Cerium(IV) in Aqueous Perchlorate Solutions: A Kinetics and Mechanistic Approach

Abstract

The kinetics of oxidation of one of the formamidine derivatives, namely, methylaminopyrazole formamidine (MAPF) by cerium(IV) has been investigated in aqueous perchlorate solutions at a constant ionic strength of 1.2 mol dm-3 and at 25°C. The progress of the reaction was followed spectrophotometrically. The reaction exhibited a first order kinetics with respect to [Ce(IV)], whereas the order with respect to [MAPF] was found to be less than unity. The reaction rate decreased with the increase in acid concentration with a negative less than unit order. The rate of reaction was not affected by increasing either ionic strength or dielectric constant of the medium. Furthermore, addition of cerium(III) product did not affect the reaction rate. The plausible oxidation mechanism involves formation of an intermediate complex between MAPF substrate and the kinetically active species of cerium(IV) in a pre-equilibrium step which decomposes in the slow step to give free radical derived from the substrate and Ce(III). The free radical is attacked by another Ce(IV) species to yield the final oxidation products which were identified by spectral and chemical analyses as methylaminopyrazole, dimethylamine and carbon dioxide. The activation parameters have been evaluated and discussed. The rate law associated with the reaction mechanism was derived.

Degradation of Nonylphenol Ethoxylate-10 (NPE-10) by Mediated Electrochemical Oxidation (MEO) Technology

“…According the results of NPE-10 degradation in the presence of Ag(I), we revealed that the performance of NPE-10 by MEO was improved. Furthermore, our data were in the line with previous studies which have reported that the presence of Ag(I) in a solution containing Ce(III) will increase the oxidation peak current of Ce(III) (Fawzy & Al-Jahdali 2016;Sumathi et al 2010;Matheswaran et al 2007). Based on the explanation above, Ag(I) has potential as a ionic catalyst in the redox reaction of Ce(III)/Ce(IV).…”