Question

A 2-ketohexose is reduced with NaBH₄ in ${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}$ to form a mixture of D-galactitol and D-talitol. What is the structure of the 2-ketohexose?

Short answer

Answer

Step-by-step solution

 Ketohexose

Ketohexoses comprises ketone as the primary functional group, and these carbohydrates possess six carbon atoms.Among several ketohexoses, one is fructose.

Reactions at the carbonyl group

Several oxidation and reduction reactions happen in the monosaccharide’s carbonyl group.

The carbonyl group of a specific aldose gets converted to alcohol using reagents like NaBH₄ and${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}$ . The alcohol acquired in this process is termed an alditol.

Structure of 2-ketohexose formed from D-galactitol and D-talitol

The 2-ketohexose reduced with NaBH₄ in ${\mathrm{CH}}_3\mathrm{OH}$ leads to D-galactitol, and D-talitol is D-tagatose. The structure of the 2-ketohexose can be given as:

Structure of 2-ketohexose

In this reaction, the carbonyl groups like aldehydes and ketones are reduced to an alcohol. The conversion of D-tagatose to D-galactitol and D-talitol can be given as:

Formation of D-galactitol and D-talitol from the 2-ketohexose, D-tagatose