Kinetics and mechanism of the oxidation of L-ascorbic acid by trisoxalatocobaltate(III) in basic aqueous solution |
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| Affiliation: | 1. Department of Chemistry, Dravidian University, Kuppam, Chittoor, 517425, Andhra Pradesh, India;2. Department of PG Studies and Research in Industrial Chemistry, Kuvempu University, Jnana Sahyadri, Shankaraghatta, Shimoga 577451, Karnataka, India;1. UCIBIO, REQUIMTE, Department of Chemical Sciences, Faculty of Pharmacy, University of Porto (FFUP), 4050-313 Porto, Portugal;2. UCIBIO, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 404169-007 Porto, Portugal;3. UCIBIO, REQUIMTE, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, 4050-313 Porto, Portugal |
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| Abstract: | The kinetics and mechanism of the oxidation of L- ascorbic acid by trisoxalatocobaltate(III) were studied as a function of pH, ascorbate concentration, ionic strength and temperature in a weakly basic aqueous solution. The pH dependence of the process can be ascribed to the oxidation of the doubly deprotonated ascorbate ion for which k = 20 M−1 s−1 at 25 °C, ΔH# = 34 ± 2 kJ mol−1 and ΔS# = −108 ± 7 J K−1 mol−1. The results are discussed in reference to literature data for this reaction in weakly acidic medium and for the oxidation by a series of other oxidants. |
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