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

Ahmed Fawzy

doi:10.11648/j.ajche.20160402.12

Abstract

The of kinetics of oxidation of a pyrimidine derivative, N,N-dimethyl-N’-(pyrimidin-2-yl) formamidine (Pym-F), by hexacyanoferrate(III) (HCF) was studied in aqueous alkaline medium in the presence of palladium(II) catalyst. The reaction did not proceed in the absence of Pd(II) catalyst. The progress of the catalyzed reaction was followed spectrophotometrically. The reaction showed a first order kinetics in both [HCF] and [Pd(II)], and less than unit orders with respect to both [Pym-F] and [OH-]. Increasing ionic strength and dielectric constant of the medium increased the reaction rate. A mechanistic scheme for the catalyzed oxidation reaction has been proposed. The final oxidation products are identified as 2-aminopyrimidine, dimethylamine and carbon dioxide. The rate law expression associated with the reaction mechanism is derived and the reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the rate-determining step have been computed and discussed.

Highlights

Pyrimidine is a six-membered heterocyclic organic compound with two nitrogen atoms at positions 1 and 3 in the ring
The pyrimidine ring system has a wide occurrence in nature as substituted, ring fused compounds and derivatives, including the nucleotides, thiamine and alloxan [1]
The results indicated that two moles of HCF are consumed by one mole of Pym-F to yield the oxidation products as shown in the following stoichiometric equation: where compound I, II and III refer to Pym-F, 2aminopyrimidine and dimethylamine, respectively

Summary

Introduction

Pyrimidine is a six-membered heterocyclic organic compound with two nitrogen atoms at positions 1 and 3 in the ring. The pyrimidine ring system has a wide occurrence in nature as substituted, ring fused compounds and derivatives, including the nucleotides, thiamine (vitamin B1) and alloxan [1]. It is found in many synthetic compounds such as barbiturates and the HIV drug, zidovudine. The N,N-dialkyl derivatives of formamidines are highly effective acaricides and the most rewarding of these studies resulted in discovery of the acaricide insecticide chlordimeform [5, 6]. The oxidative cleavage of formamidines is quite important, since the N,N-dialkyl formamidine group is one of the most versatile protecting groups, especially in biosynthetic applications

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