28. Carbohydrates

Determine the structure of the alditol formed when b-D-xylofuranose is treated with NaBH4 and then water. Explain how NaBH4 can reduce the hemiacetal group of the furanose.

What product or products are obtained when D-galactose reacts with each of the following?

c. NaBH₄, followed by H₃O⁺

Predict the products obtained when D-galactose reacts with each reagent.

(h) NaBH₄

Predict the products obtained when D-galactose reacts with each reagent.

(e) H₂, Ni

Identify the sugar in each description.

a. An aldopentose that is not D-arabinose forms D-arabinitol when it is reduced with NaBH₄.

Identify the sugar in each description.

c. A ketose that, when reduced with NaBH₄, forms D-altritol and D-allitol.

What monosaccharide is reduced to two alditols, one of which is the alditol obtained from the reduction of

1. D-talose? 

2. D-allose?

When D-glucose is reduced with sodium borohydride, optically active glucitol results. When optically active D-galactose is reduced, however, the product is optically inactive. Explain this loss of optical activity.