# How can separate samples of optical isomers be distinguished?

May 26, 2016

By their rotation of plane-polarized light.

#### Explanation:

Given separate quantities of $R$ and $S$ enantiomers (and it is by no means trivial to obtain such samples!), one enantiomer will rotate plane-polarized light by some angle $\alpha$. It enantiomer, its optical antipode, will rotate plane-polarized light in the opposite direction, i.e. by an angle $- \alpha$.

Lanthanide shift reagents could be used to obtain the NMR spectra of the enantiomers (these would give a diastereomic spectrum because of the chiral shift reagent), though this is another specialized experiment.

What do you think would be the action of chiral medicines and drugs on our biochemistry?

See this older answer for details on the separation of optical isomers.