Chapter 17, Problem 2Q

Interpretation Introduction

Interpretation:

$\text{ee}\%$ and molecular composition of a sample of $2-\text{butanol}$ when specific rotation is $-9.75°$ isto be determined.

Concept introduction:

Optical activity is the ability of substances to rotate plane-polarized light when it falls on it.

A molecule is called chiral if it possesses no plane of symmetry and is not superimposable on its mirror image. A molecule that has a tetrahedral atom with four different substituents known as stereocenter is chiral. A stereocenter is also called a chiral or asymmetric center. Chiral compounds exhibit the property of enantiomerism. Enantiomers are stereoisomers that have non-superimposable mirror images.

The magnitude of the optical rotation relies on the concentration of the optically active compound, the length of the path of light that passes through the solution, the wavelength of the light, the nature of the solvent, and the temperature. The optical rotation is shown by the symbol ${\text{[α]}}_{\text{λ}}^{\text{T°}}$ known as specific rotation. and is an inherent property of a pure optically active compound. $\text{T°}$ is the temperature of the measurement in degrees Celsius, and $\text{λ}$ is the wavelength of light used. The purity of optically active compounds is expressed as an enantiomeric excess.