Chapter 14.4, Problem 14.15P

(a)

Interpretation Introduction

Interpretation:

Product that is formed when D-arabinose is treated with hydrogen in presence of palladium has to be given.

Concept Introduction:

Carbohydrates undergo reduction similar to an alkene.  When an aldose is treated with hydrogen in presence of palladium as catalyst the carbonyl group present in the aldose is reduced resulting in formation of alditol.  This is also known as “sugar alcohol”.

(b)

Interpretation Introduction

Interpretation:

Product that will be formed when D-arabinose is treated with Benedict’s reagent has to be drawn.

Concept Introduction:

Monosaccharides that are aldoses contains an aldehyde group.  The carbonyl of the aldehyde undergoes oxidation very easily resulting in the formation of carboxyl group.  The product formed is known as aldonic acid.  Benedict’s reagent is ${\text{Cu}}^{\text{2+}}$.  The monosaccharides that contains aldehyde group are known as reducing sugars.  In the course of the reaction, Benedict’s reagent is reduced to ${\text{Cu}}^{\text{+}}$.  General reaction can be represented as follows.

    ${\text{Aldose + 2Cu}}^{\text{2+}}\to \text{Aldonic}{\text{acid + Cu}}_{\text{2}}\text{O}$