Chapter 5, Problem 10Q

Interpretation Introduction

Interpretation:

The number of stereoisomers of the given Fischer projection are to be determined.

Concept introduction:

Isomers are the molecules that have the same number of atoms, but have different arrangement of the atoms in the space.

Stereoisomers have the same molecular formula, but the arrangement of atoms in the three-dimensional orientation is different.

Enantiomers are the stereoisomers whose molecules have chiral center and the molecules are mirror image to each other.

The objects or molecules that 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.

Chiral molecules are capable of rotating plane polarized light

The molecules that are superimposable or identical with their mirror images are known as achiral molecules, and achiral molecules are not capable of rotating the plane-polarised light.

Plane of symmetry is the plane that bisects the molecule in two equal halves, such that they are mirror images of each other.

Compounds having plane of symmetry are usually achiral as they do not have different atoms around the central carbon atom.

The number of stereoisomers, due to the presence of the chiral center, is calculated by using the expression as follows:

$\text{Number}\text{of}\text{stereoisomers}=2^n$.

Here, $n$ is the number of chiral centers present in the compound.