Kinetic and Mechanism of Oxidation of Methylaminopyrazole Formamidine by Alkaline Hexacyanoferrate(III) and the Effect of Divalent Transition Metal Ions

Abstract

In aqueous alkaline medium, the kinetics of oxidation of methylaminopyrazole formamidine (MAPF) by hexacyanoferrate(III) (HCF)has been studied spectrophotometrically under the conditions, MAPF >> HCF at a constant ionic strength of 0.1 mol dm-3 and at 25°C. The reaction showed first order dependence on [HCF] while it exhibited fractional-first order kinetics with respect to [MAPF] and [OH-]. The oxidation rate increased with increasing ionic strength and dielectric constant of the reaction medium. Addition of small amounts of some divalent transition metal ions accelerates the oxidation rate and the order of catalytic efficiency was: Cu(II) > Ni(II) > Zn(II) > Co(II) > Cd(II). The suggested mechanism involves formation of a 1: 1 intermediate complex between HCF and the deprotonated MAPF species in a pre-equilibrium step. The final oxidation products were identified as methylaminopyrazole, dimethylamine and carbon dioxide. The appropriate rate law was deduced. The reaction constants involved in the mechanism were evaluated. The activation and thermodynamic parameters were determined and discussed.

Kinetics and Mechanism of the Oxidation of 2-Methylindole by Alkaline Potassium Hexacyanoferrate(iii)

“…Although the oxidation of certain substituted indoles by a wide variety of oxidizing agents has been reported in the literature [8], the lack of kinetic and mechanistic investigation on the oxidation of indoles by potassium hexacyanoferrate(III) instigated us to carry out this work. The usefulness of hexacyanoferrate(III) is due to its high stability, water solubility and its moderate reduction potential, leading to its reduction to hexacyanoferrate(II), a stable product [9,10].…”

A Study of the Kinetics and Mechanism of Oxidation of Fluorene by Alkaline Hexacyanoferrate(III)

“…Moreover, fluorene is considered as effective and pronounced precursor for synthesis of photochromic di and tetrahydroindolizines [11][12][13][14]. On the other hand, oxidation of organic compounds by hexacyanoferrate (III) has been a subject of much interest especially in alkaline media [15][16][17][18][19][20][21][22][23][24][25][26] because hexacyanoferrate (III) has a high stability, water solubility and moderate reduction potential [27]. A literature survey revealed no work has been reported about the kinetics of oxidation of fluorene by any oxidant.…”

Palladium(II)-Catalyzed Oxidation of Pyrimidine Derivative by Hexacyanoferrate(III) in Aqueous Alkaline Medium: A Kinetic Study

“…On the other hand, formamidines form complexes with transition metal ions [7,8] and such complexes exhibit remarkable biological activity against certain microbes, viruses and tumors [9,10]. The presence of heteroatom in such ligands plays a key role when coordinated with these metal ions such as pyrimidine derivatives.…”

“…Hexacyanoferrate(III) is an efficient one-electron oxidant for oxidation of various organic compounds especially in alkaline media [7,8,[15][16][17][18][19][20][21][22][23][24][25][26]. The usefulness of HCF may be due to its high stability, water solubility and its moderate reduction potential of 0.45 V, leading to its reduction to HCF(II), a stable product [27].…”