Chapter 18, Problem 18.79P

Interpretation Introduction

Interpretation:

The solution of the $\text{α}$ form of D-galactose rotates plane-polarized light $+150.7°$ whereas the solution of the $\text{β}$ form rotates the light $+52.8°$. Over time, both solutions have the same measured rotation of $+80.2°$. How much of the equilibrated solution does each form account for is to be calculated.

Concept introduction:

The specific rotation is the angle of rotation of light of the given wavelength when it passes through a sample whose concentration is $\text{1 g/mL}$ and length is $\text{1 dm}$ at a given temperature. The specific rotation is the characteristic property of the given chiral compound. The term anomer is specifically used in carbohydrate chemistry, instead of diastereomers. When a mixture of the anomers is dissolved in the solution, the resulting specific rotation changes at equilibrium. The specific rotation at equilibrium depends on the anomer which is excess in solution and whose specific rotation is more than other.