Which one of the following on reduction with NaBH₄ gives equimolar mixture of sorbitol and mannitol.

Answer: The compound that gives an equimolar mixture of sorbitol and mannitol on reduction with sodium borohydride (NaBH₄) is D-fructose.

Explanation:

• D-Fructose is a ketohexose, which contains a ketone group. Upon reduction with NaBH₄, the ketone group is converted into a secondary alcohol.
• Since D-fructose has a chiral center adjacent to the carbonyl group, reduction leads to the formation of two diastereomers: sorbitol (D-glucitol) and mannitol.
• These diastereomers are formed in equimolar amounts because the reduction of the ketone group can occur from either side of the planar carbonyl group, leading to equal probabilities of forming each product.

Reaction:

D-Fructose + NaBH₄ → Sorbitol + Mannitol

This process is widely used in the food and pharmaceutical industries for producing sugar alcohols.