Chapter 5.4, Problem 18ATS

Interpretation Introduction

Interpretation:

Observed specific rotation, $\left[\alpha \right]$ for the given sample 1 has to be determined.

Concept Introduction:

The specific rotation, [α], is a fundamental property of chiral substances that is expressed as the angle to which the material causes polarized light to rotate at a particular temperature, wavelength, and concentration.

The specific rotation of a molecule can be calculated by using the formula given below.

  ${[\alpha ]}^T{}_{{}_{{}_{\lambda }}}=\frac{{\alpha }_{obs}(\mathrm{deg}ree)}{l(dm).C(\frac{g}{mL})}$

$\begin{array}{l}\text{alpha }\left(\text{α}\right)\text{ represents the observed rotation measured with a polarimeter}\text{.}\\ \text{ l represents the length of the sample tube}\text{. }\\ \text{C is the concentration of a solution of a pure sample}\text{.}\\ \text{λ is the wave length of the light}\text{.}\end{array}$

Enantiomeric excess: The ($ee$) is a measurement of purity for chiral substances, and its reflected the degree to which a sample contains one enantiomer in greater amounts then the other.

The following equation can be used to calculate the % ($ee$)

$\text{enantiomeric excess}\text{(ee) (\%) = }\frac{[observed\alpha ]}{[\alpha \text{of}\text{pure}\text{enantiomer}]}\times 100$