20. Carbohydrates

Determine which aldose reactant should be used to produce the following sugar alcohol.

What is the common name of the sugar alcohol produced when D-galactose is reduced?

Draw the Fischer projection for the reduction product of D-mannose, the C-2 epimer of glucose. What is the structure and common name of the sugar alcohol produced? 

Reduction of d-fructose with a reducing agent yields a mixture of d-sorbitol along with a second, isomeric product. What is the structure of the second product?

Treatment of d-glucose with a reducing agent yields sorbitol, a substance used as a sugar substitute by people with diabetes. Draw the structure of sorbitol.

Use the Fischer projection for d-gulose in problem 13.69 to answer each of the following: (13.3, 13.5)

a. Draw the Fischer projection and name the product formed by the reduction of d-gulose.

ALLIED Health The sugar alcohol ribitol is a component of the vitamin riboflavin and the energy transfer molecule FAD. Ribitol is formed when the monosaccharide ribose undergoes reduction at carbon 1. Draw the structure of ribitol.

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d-Ribose

ALLIED Health The sugar alcohol erythritol is often included in low-calorie sweeteners. It is 70% as sweet as table sugar. Erythritol is the reduced form of the aldotetrose erythrose. Draw erythritol.

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d-Erythrose

Draw the Fischer projection of the product of reduction reaction of d-galactose at C1

In Section 15.6, you saw that aldehydes react with reducing agents to yield primary alcohols (RCH=O → RCH₂OH). The structures of two d-aldotetroses are shown. One of them can be reduced to yield a chiral product, but the other yields an achiral product. Explain. <IMAGE><IMAGE>