Year-end Sale % OFF 
Abstract
The kinetics of chromic acid oxidation of one of aminopyrazole formamidine derivatives, namely N,N-dimethyl-N’ -(5-methyl-1H-pyrazol-3-yl) formamidine (MAPF)in sulfuric acid solutions has been investigated at constant ionic strength and temperature. The progress of the reaction was followed spectrophotometrically. The reaction showed a first order dependence on [chromic acid] and fractional-first order dependences with respect to [MAPF] and [H+]. Increasing ionic strength and solvent polarity of the reaction medium had no significant effect on the oxidation rate. Addition of AgI, PdII and RuIII catalysts was found to enhance the reaction rate and the order of catalytic efficiency is: AgI > RuIII > PdII. The final oxidation products of MAPF are identified by spectral and elemental analysis as methylaminopyrazole, dimethylamine and carbon dioxide. A spectral evidence for the formation of chromium(III) product was obtained. A reaction mechanism adequately describing the observed kinetic behavior is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-determining step of the reaction, along with thermodynamic quantities of the equilibrium constants, are presented and discussed.
Highlights
During the few last decades, formamidines have achieved considerable attention because they have a unique and fascinating biological activity including monoamine oxidase inhibitors [1, 2], adrenergic and neuro-chemical receptors [3, 4]
The stoichiometry was determined spectrophotometrically which indicates consumption of two moles of chromic acid for three mole of methylaminopyrazole formamidine (MAPF) to yield the oxidation products as shown in the following equation, where MAP refers to methylaminopyrazole
The spectral changes during the oxidation of MAPF by chromic acid in aqueous sulfuric acid solution are shown in Figures 1 and 2
Summary
During the few last decades, formamidines have achieved considerable attention because they have a unique and fascinating biological activity including monoamine oxidase inhibitors [1, 2], adrenergic and neuro-chemical receptors [3, 4]. The oxidative cleavage of formamidine derivatives is important because it yields N,N-dialkyl formamidine group which has various biosynthetic applications. Formamidines may play an important role in the chemistry of chromium, especially in the environment because of its mutagenic and carcinogenic activity. Chromium in aqueous solutions exists in both trivalent, CrIII, and hexavalent, CrVI, species. These two oxidation states are characterized by different physical/chemical behavior and toxicity. It can be reduced to lower oxidation states by various biological and chemical reductants [6]. The chemistry of the intermediate oxidation states of chromium, CrV and CrIV, which observed during the oxidation of organic substrates by chromium(VI) was attracted many researchers because of their implication in the mechanism of chromium–induced cancers [7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
