Chapter 16, Problem 16.72QP

Interpretation Introduction

Interpretation:

Reason for ketoses being oxidized in Benedict’s test while ketones are not oxidized has to be given.

Concept Introduction:

Benedict test is oxidation of aldehyde group present in aldoses.  The reagent used contains ${\text{Cu}}^{\text{2+}}$ ions that is reduced to ${\text{Cu}}^{\text{+}}$ ions when treated with aldoses.  A brick-red precipitate of ${\text{Cu}}_{\text{2}}\text{O}$ confirms the presence of aldehyde functional group.  Aldehyde group is oxidized to carboxylic acid.  If a hemiacetal hydroxyl group is present in the sugar then it will be a reducing sugar and the result will be positive for Benedict’s test.