Chapter 22, Problem 6Q

Interpretation Introduction

Interpretation:

Haworth and conformational formulae of the $\beta$ -cyclic hemiacetal of D-mannose are to be completed. The nature of the hemiacetal on the basis of the given reactions and observations is to be determined.

Concept introduction:

The Haworth representation of the chemical formulae of biomolecules demonstrates the cyclic form of monosaccharides with a simple three-dimensional perspective. It represents the chirality center of the open-chain form through the cyclic forms. Carbon is an implicit type of atom. Carbons are numbered from 1 to number 6, where the first carbon is called the anomeric carbon.

Identification of carbohydrates is carried out by the anomeric carbons. If the hydroxyl group is attached to the anomeric carbon, the carbohydrate is reducible, which positively tested for Benedict and Tollens’s test.

The optical activity of a carbohydrate is dependent on its ability to turn the plane of polarized light incident on the sample.

When monosaccharides react with dilute nitric acid, the aldehydes and alcohols are oxidized into carboxylic acids, producing dicarboxylic acids known as aldonic acids.

Aldehydes and ketones can be reduced to primary and secondary alcohols, respectively, with the help of sodium borohydride.