Question

Why fructose on reduction gives a mixture of mannitol and sorbitol?

Answer 1

Mannitol is used clinically in osmotherapy to reduce acutely raised intracranial pressure until more definitive treatment ...

Answer 2

Fructose yields a mixture of mannitol and sorbitol on reduction due to the generation of a new asymmetric carbon atom.

• Fructose has a keto functional group, that is, it is a ketose sugar.
• On reduction,  this carbon with keto group gets a hydroxyl group and hydrogen atom. Thus, four different groups are attached to the carbon, making it asymmetric or chiral.
• The hydroxyl and hydrogen groups on a chiral carbon can differ in the arrangement, forming two different isomers. Mannitol and sorbitol are the results of such isomerism.
• Mannitol and sorbitol differ in configuration at only one carbon atom. so they are epimers.