Chapter 21, Problem 33P

a)

Interpretation Introduction

Interpretation:

An aldopentose that is not D-arabinose and forms D-arabinitol on reduction with ${\text{NaBH}}_{\text{4}}$ is to be identified.

Concept Introduction:

Pentoses are the sugar compounds that belong to five membered monosaccharide units. In the compound of aldopentose an aldehydic functional group is present at the position $1$.  D-arabinose is the example of aldopentose.

b)

Interpretation Introduction

Interpretation:

A sugar that is not D-altrose and forms D-altraric acid on oxidation with nitric acid has to be identifed.

Concept Introduction:

D-altrose is a monosaccharide which contains six carbons and aldehyde group.  It exists in D and L forms.  It is formed from dietary lactose.  It is soluble in water but not in methanol.  It is an epimer of mannose sugar.

c)

Interpretation Introduction

Interpretation:

A ketose that is reduced with ${\text{NaBH}}_{\text{4}}$, forms D-altritole and D-allitol has to be identified.

Concept Introduction:

Ketose is a monosaccharide molecule and it contains a ketonic group. Dihydroxyacetone is the simplest ketose molecule with three carbon atoms. ${\text{NaBH}}_{\text{4}}$ is a good reducing agent. It reduces aldehydic group to the alcoholic group in the presence of ${\text{H}}_{\text{3}}{\text{O}}^{+}$.