Preparation of dehydro-L-ascorbic acid dimer by air oxidation of L-ascorbic acid in the presence of catalytic amounts of copper(II) acetate and pyridine.
The catalytic system Cu(AcO)2-pyridine 1:4 mol% in methanol, slowly catalyses the air oxidation of ascorbic acid to the 2-methyl hemi-ketal of dehydroascorbic acid 5, and hydrogen peroxide. However, with Cu(AcO)2-pyridine 3:4 mol% the air oxidation is quite fast and no hydrogen peroxide is present at the end of the reaction. Removal of the catalyst and refluxing the foamy 5 in MeCN gives the oxidized, dimeric, dehydroascorbic acid in very good yields (approximately 70%) contaminated by approximately 1-2% MeCN.
Koliou
Eleftheria K
EK
Department of Chemistry, University of Patras, GRC-26500 Patras, Greece.
Ioannou
Panayiotis V
PV
D001205:Ascorbic Acid / Q000031:analogs & derivatives / Q000737:chemistry*; D002384:Catalysis; D003460:Crystallization; D003683:Dehydroascorbic Acid / Q000138:chemical synthesis* / Q000737:chemistry*; D019281:Dimerization; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011725:Pyridines / Q000737:chemistry*
D009942:Organometallic Compounds; D011725:Pyridines; C015092:cupric acetate; C023666:pyridine; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid