Periodate Oxidation of Carbohydrates

Periodate Oxidation of Carbohydrates

• There are three analytical methods for studying periodate oxidation of polyhydroxy compounds: iodometric, acidimetric, and spectrophotometric.
• Compounds containing hydroxyl groups on adjacent carbon atoms undergo qualitative oxidation at room temperature with an excess of periodic acid or its salts.
• Periodic acid (HIO4) is a useful reagent in carbohydrate analysis, cleaving C—C bonds if:
  • Both carbons have hydroxyl groups
  • One carbon has a hydroxyl group and is adjacent to another carbon with an amino group, keto, or aldo oxygen
• Every cleavage results in an oxidation, with the carbon participating in the cleavage reaction being oxidized to the next level (e.g., alcohol to aldehyde, aldehyde to carboxylic)
• The hemiacetal C in a glycosidic linkage or methylated reduces the sites of possible cleavage due to the inability to open-out the ring structure into a straight chain
• Periodate oxidation consumes one mole of periodate and produces one mole each of iodate and water for every pair of vicinal hydroxyl groups
• Periodate reacts with iodide in neutral solution to give iodine and iodate, requiring alkaline conditions to prevent iodate from oxidizing iodide to iodine
• NaHCO3 is added to maintain alkaline conditions
• Iodine formed is immediately reacted with arsenite, which is added at the end of the periodate oxidation