Chapter 5, Problem 46P

Interpretation Introduction

Interpretation:

$\left(R\right)$ or $\left(S\right)$ designation for each chirality center of aspartame is to be given.

Concept introduction:

The moleculesthat are nonsuperimposable or not identical with their mirror images are known as chiral molecules.

A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active.

The objects or moleculesthat are superimposable with their mirror images are achiral objects or molecules and these objects have a centre of symmetry or plane of symmetry.

The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive.

The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers.

Priority is given to all the four groups attached to the chirality center.

Priority is given on the basis of atomic number of the atom. The higher the atomic number, the higher will be the priority.

If priority cannot be assigned according to atomic mass, then priority is assigned according to first point of difference.

After giving priority to four groups, rotate the molecule such that the fourth priority group is away from the observer.

Now, move from a to b to c; if the direction is clockwise, then designate it as $\left(R\right)$, and if the direction is anti-clockwise, then designate it as $\left(S\right)$.

When the order of progression from the group of highest priority to that of the next highest priority is clockwise, it is said to be the $\left(R\right)$ configuration

When the order of progression from the group of highest priority to that of the next highest priority is anticlockwise, then it is said to be the $\left(S\right)$ configuration.

Aspartame is an artificial sweetener.