Mechanistic aspects of uncatalyzed and ruthenium(iii) catalyzed oxidation of 1,4-dioxane by a copper(iii) periodate complex in aqueous alkaline medium

Abstract

Oxidation of 1,4-dioxane (Dio) by a copper(III) periodate complex (DPC) has been investigated spectrophotometrically both in the absence and presence of a ruthenium(III) catalyst in aqueous alkaline medium at 298 K. Stoichiometry of (1 : 8) was observed in both the reactions and the order of the reaction with respect to [DPC] was unity while the order with respect to [Dio] was <1 over the concentration range studied. Order with respect to [OH⁻] and [IO₄⁻] had negative order in both cases. Order with respect to [Ru(III)] was unity. The activation parameters (ΔH^# = 38 ± 2 kJ mol⁻¹, ΔS^# = −164 ± 15 J K⁻¹ mol⁻¹ and ΔG^# = 87 ± 4 for uncatalyzed and ΔH^# = 34 ± 3 kJ mol⁻¹, ΔS^# = −43 ± 2 J K⁻¹ mol⁻¹ and ΔG^# = 47 ± 3 for catalyzed reaction) with respect to the slow step of the proposed mechanism were computed and thermodynamic quantities were also calculated. Kinetic studies suggest that [Cu(OH)₂(H₃IO₆)]⁻ is the reactive copper(III) species and [Ru(H₂O)₅(OH)]²⁺ is the reactive Ru(III) species.