Conversion of Glucose to Arabinose (Wohl's Method)
Aldohexose to Aldopentose Conversion
The conversion of an aldohexose (like D-Glucose) to an aldopentose (like D-Arabinose) is efficiently achieved using Wohl's Method. This process involves the degradation of the carbon chain by one unit.
The Chemical Mechanism
The mechanism follows these critical steps:
- Oxime Formation: Aldose reacts with hydroxylamine to form the corresponding aldoxime.
- Dehydration & Acetylation: Treatment with acetic anhydride and ZnCl2 dehydrates the oxime group and esterifies hydroxyl groups to produce acetylated aldonitrile.
- HCN Elimination: Warmed with ammoniacal silver oxide, the acetyl groups are removed, and a molecule of HCN is eliminated, resulting in an aldose with one less carbon.