Kinetics and Mechanistic Study of Oxidation of Pyridine Derivative by Cerium(IV) in Aqueous Perchloric Acid

Ahmed Fawzy

doi:10.11648/j.ajpc.20160501.12

Abstract

The kinetics of oxidation of N, N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F) by cerium(IV) was studied spectrophotometrically in aqueous perchloric acid solutions at a constant ionic strength of 1.0 mol dm-3 and at 20°C. The reaction showed first order dependence with respect to [Ce(IV)] and less than unit order with respect to [Py-F]. The reaction exhibited negative fractional-first order kinetics with respect to [H+]. The rate of reaction was not significantly affected by variation of either ionic strength or dielectric constant of the reaction medium. Addition of cerium(III) product did not affect the reaction rate. A suitable mechanistic scheme for the oxidation reaction has been proposed. The final oxidation products were identified as 2-aminopyridine, dimethylamine and carbon dioxide. The activation parameters have been evaluated and discussed. The rate law associated with the reaction mechanism was derived.

Highlights

Aminopyridine is an important organic compound which is used in the production of the drugs piroxicam, sulfa pyridine, tenoxicam, and tripelennamine
The N, N-dialkyl derivatives are highly effective acaricides and the most rewarding of these studies resulted in the discovery of acaricide insecticide chlordimeform
Reaction mixtures containing various amounts of Ce(IV) and Py-F at constant [H+], ionic strength and temperature were allowed to react for 24 h in closed vessels for completion of reactions

Summary

Introduction

Aminopyridine is an important organic compound which is used in the production of the drugs piroxicam, sulfa pyridine, tenoxicam, and tripelennamine. 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. Oxidation by cerium(IV) in sulfuric acid solutions have conclusively been established [5,6,7,8,9,10,11,12,13]. The reactions of cerium(IV) in perchloric acid medium proceed much faster than those in sulfuric acid medium. Cerium(IV) oxidations of various substrates are found to follow different mechanisms, depending upon the acid medium used. Such oxidation are generally interesting to understand the different pathways of the reactions and different active forms of cerium(IV)

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