Chapter 5, Problem 53P

Interpretation Introduction

Interpretation:

The observed rotations are to be determined, and if the optical rotation of a substance studied at only one concentration is zero, then whether it can be concluded as the achiral or racemic mixture or not is to be stated with given concentration, observed rotation, wavelength, path length of the tube, and temperature.

Concept introduction:

The molecules that 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 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 stereo formula, which is depicted in two dimensions, in which stereochemical information is not destroyed, is determined by Fisher Projection formula.

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-polarized light.

The observed rotation is calculated as ${[\alpha ]}_{\text{D}}=\frac{\alpha }{\text{cl}}$, where $\left[\alpha \right]$ is the observed rotation, $\alpha$ is the observed rotation in degrees, $c$ is the concentration, and $l$ is the path length.