Enantiomers have almost all the same physical properties, melting points, boiling points, solubility. They only differ in the rotation of polarized light, the dextrorotatory rotates to the right and the levorotatory to the left. Therefore the separation of enantiomers cannot be carried out by conventional physical methods (distillation, crystallization.....). The solution to the problem is based on the difference between the physical properties of the diastereoisomers, which do have different melting, boiling and solubility points that allow them to be separated.

 

We are going to look for a reaction that converts the racemic mixture into a mixture of diastereoisomers, by binding each enantiomer to a chiral reagent. This mixture is separated by fractional crystallization, distillation or chromatography of the diastereoisomers. Finally, the bond that unites each enantiomer with the chiral reagent is broken and both are separated, obtaining the pure enantiomers.