Kinetics and mechanism of oxidation of diethylamine and triethylamine by [Ru^V=O(EDTA)]⁻ in aqueous medium

Abstract

The kinetics of oxidation of diethylamine and triethylamine by [Ru^V=O(EDTA)]⁻ were studied spectrophotometrically as a function of [Ru^V=O(EDTA)]⁻ and [amine] at a fixed pH of 5.0 and ionic strength of 0.2 M NaClO₄. The reaction rate was followed by observing the disappearance of the characteristic peak at 393 nm of the oxo complex Ru^V=O(EDTA)⁻ with time. Oxidative N-dealkylation of tertiary and secondary amines produces secondary and primary amines respectively as oxidation products, the N-alkyl group being oxidized to the corresponding aldehyde. The oxidation reactions were studied at three different temperatures and activation parameters (ΔH‡ and ΔS‡) calculated. A mechanism involving a hydride shift from the α-carbon of the substrate to the oxo oxygen is proposed for the oxidation of amines by Ru^V=O(EDTA)⁻. The experimental results are discussed with reference to the oxidation of the corresponding amines with molecular oxygen catalysed by the [Ru^III(EDTA)(H₂O)]⁻ complex.