Mechanistic Investigations of Uncatalyzed and Ruthenium(III) Catalyzed Oxidation of Vanillin by Periodate in Aqueous Alkaline Medium

• Published in: Journal of solution chemistry 2015-06, Vol.44 (6), p.1205-1223
• Main Authors: Patil, Deepa G., Magdum, Prashant A., Nandibewoor, Sharanappa T.
• Format: Article
• Language: English
• Subjects: Activation; Catalysis; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Constants; Geochemistry; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Mathematical analysis; Oceanography; Oxidation; Physical Chemistry; Reaction kinetics; Strength; Vanillin
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-015-0341-1

The kinetics and mechanism of uncatalyzed and ruthenium(III) catalyzed oxidation of vanillin (Van) by periodate were studied in alkaline medium at 298 K, and at constant ionic strength of 0.3 mol·dm −3 . The reaction exhibits 1:1 stoichiometry ([Van]:[periodate]). The reaction shows first-order kinetics in [periodate] and [Ru(III)] and less than unit order with respect to [Van] and [OH − ]. The ionic strength and dielectric constant of the medium did not affect the rate significantly. The main products were identified by spot tests, melting temperature and FT-IR. From the effect of temperature on the reaction rate, the Arrhenius and activation parameters have been calculated. The catalytic constant ( K C ) was also calculated for Ru(III) catalysis at different temperatures. Plausible mechanisms have been proposed and rate laws explaining the experimental results are derived. Kinetic studies suggest that the active species of periodate and Ru(III) were [H 2 IO 6 ] 3− and [Ru(H 2 O) 5 OH] 2+ , respectively. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism, along with the corresponding thermodynamic quantities, were determined and discussed.