Chapter 5, Problem 5.64P

Interpretation Introduction

Interpretation:

It is to be determined how many $\text{D-aldoheptoses}$ are possible. The Fischer projection of one of them and its enantiomer is to be drawn.

Concept introduction:

The monosaccharide with seven carbon atoms is heptose. The functional group present in aldoheptoses is aldehyde. The functional group is situated at C1 carbon atom. Any D-sugar is distinguished by having the $\text{OH}$ group of the highest numbered asymmetric carbon appear on the right in its Fischer projection.

Stereoisomers that differ in their spatial arrangement of atoms and are non-superimposable on their mirror image are called chiral molecules. The asymmetric center in the molecule is called the chiral center. The molecules having non-superimposable mirror images are enantiomers.

The maximum number of stereoisomers that can exist for a given molecule is calculated by the formula ${\text{2}}^{\text{n}}$, where n is the number of chiral centers in the molecule. A molecule is meso if it contains at least two chiral centers but has a plane of symmetry that makes it achiral. Achiral compounds are optically inactive.