Kinetics and mechanism of the chromic oxidation of 3-O-methyl-D-glucopyranose

FRASCAROLI MARÍA INES; SALAS PEREGRIN, JUAN MANUEL; SALA LUIS F; SIGNORELLA,SANDRA

POLYHEDRON

Elsevier

Lugar: USA; Año: 2009 vol. 28 p. 1049 - 1056

0277-5387

The oxidation of 3-O-methyl-D-glucopyranose (Glc3Me) by CrVI in acid medium yields CrIII, formic acid and 2-O-methyl-D-arabinose as final products when a 50-times or higher excess of Glc3Me over CrVI is used. The redox reaction takes place through the combination of CrVI?CrIV?CrII and CrVI?CrIV?CrIIIO-methyl-D-glucopyranose (Glc3Me) by CrVI in acid medium yields CrIII, formic acid and 2-O-methyl-D-arabinose as final products when a 50-times or higher excess of Glc3Me over CrVI is used. The redox reaction takes place through the combination of CrVI?CrIV?CrII and CrVI?CrIV?CrIIIO-methyl-D-arabinose as final products when a 50-times or higher excess of Glc3Me over CrVI is used. The redox reaction takes place through the combination of CrVI?CrIV?CrII and CrVI?CrIV?CrIIIVI?CrIV?CrII and CrVI?CrIV?CrIII pathways. Intermediacy of free radicals and CrII in the reaction was demonstrated by the observation of induced polymerization of acrylamide and detection of CrO2 2+ formed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidII in the reaction was demonstrated by the observation of induced polymerization of acrylamide and detection of CrO2 2+ formed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acid2 2+ formed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidformed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acidVI distinguishes this derivative from glucose, which is oxidized to gluconic acid