# How do you find enantiomeric excess?

Feb 14, 2016

You divide the observed specific rotation by the maximum specific rotation.

#### Explanation:

EXAMPLE

A compound X has a specific rotation of -20 °. A mixture with its enantiomer has a specific rotation of -10 °. What is the enantiomeric excess (ee) of X?

Solution

The enantiomeric excess is

ee = "observed specific rotation"/"maximum specific rotation" × 100 % = ("-10" color(red)(cancel(color(black)(°))))/("-20" color(red)(cancel(color(black)(°)))) × 100 % = 50 %