Kiliani-Fischer Cyanohydrin Synthesis
The Kiliani-Fischer synthesis is used to increase the carbon chain length of an aldose by one carbon atom. The process converts an aldopentose (like D-Arabinose) into a mixture of two epimeric aldohexoses (D-Glucose and D-Mannose).
Mechanism Steps
- Cyanohydrin Formation: The aldose reacts with HCN, creating a new asymmetric center and producing two isomeric cyanohydrins.
- Hydrolysis: The cyanohydrins are hydrolyzed with dilute acid to form corresponding aldonic acids.
- Lactonization: Heating the aldonic acids results in the loss of water, forming γ-lactones.
- Reduction: The lactones are reduced using Lithium Aluminum Hydride (LAH) or Na-Hg in a weakly acidic solution to yield the final aldoses.