Kinetics of the degradative oxidation of sugar-type ligands catalyzed by copper(II) ions

摘要: Abstract The autoxidation of gluconate (Gluc) and glucuronate (GlcA) catalyzed by copper(II) ions was studied in alkaline medium (pH 13), at 30.0±0.1 °C, monitoring the oxygen uptake oxidative degradation ligands. Different complexes copper with were obtained, their reactivities compared. compound [Cu(Gluc)2] is commercially available, while Na[Cu(Gluc)(OH)] isolated pH 11.5. A third complex, dimeric Na2[Cu2(Gluc)2(OH)2], obtained 5.0. most active complex Na[Cu(Gluc)(OH)], showing a first-order dependence on both concentrations. saturation effect observed when large excess added to reaction solution. Induction periods ca. 90 min also presence gluconate. second-order rate constant k=(1.44±0.09)×10−3 mol−1 dm3 s−1 determined, based manometric measurements consumed oxygen. Comparative studies revealed faster oxidation ions, k=(2.5±0.3) s−1. Free radicals detected as reactive intermediates these oxidations EPR spectroscopy, using DMPO or POBN spin traps. Evidence degradative ligands formation formate, glycolate carbonate resulting from carbon–carbon bond cleavage, monitored capillary electrophoresis.