Resolution of Racemic Mixture

Resolution of Racemic Mixture is the process of separating two enantiomers from a racemic mixture to obtain optically active forms.

• Since enantiomers have identical physical properties (melting point, solubility, etc.), they cannot be separated by normal methods.
• So, we need special techniques to separate them — this process is called resolution.

Definition:

• Resolution is the process of separating the two enantiomers in a racemic mixture to obtain the individual optically active forms.

Methods of Resolution

1. Mechanical Separation

   • Only works for crystalline enantiomers that form distinct crystal shapes
   • Crystals of different enantiomers can sometimes be manually separated under a microscope
   • Rarely used, very limited applicability

2. Chemical Resolution (Most Common Method)

   • Involves:
     • Reacting the racemic mixture with a chiral resolving agent
     • This forms diastereomeric salts or compounds, which do not have identical properties
     • They can then be separated by crystallization or other physical means
     • After separation, the chiral agent is removed to recover the pure enantiomers
   • Example:
     • Racemic mixture of a carboxylic acid can be reacted with chiral base like quinine to form diastereomeric salts.

3. Biochemical Resolution

   • Uses enzymes or microorganisms that selectively react with one enantiomer
   • For example, yeast may ferment only one enantiomer of a racemic alcohol

4. Chromatographic Resolution

   • Chiral chromatography columns are used
   • Enantiomers travel at different speeds due to their interaction with the chiral stationary phase
   • Widely used in analytical chemistry and industry

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!