Chiral resolution
Introduction
Chiral resolution or optical resolution is a process for the separation of racemic compounds into their enantiomersEnantiomer. It is an important process in the field of chemistry, particularly in areas such as pharmaceuticals, where the different enantiomers of a molecule can have different biological effects.
Chirality
Chirality is a property of asymmetry important in several branches of science including chemistry, physics, and biology. The word "chiral" is derived from the Greek word for hand, "cheir". The most common example of chirality is the difference between left and right hands, which are mirror images of each other but cannot be superimposed. In chemistry, chirality usually refers to molecules. Two mirror images of a chiral molecule are called enantiomers or optical isomers. Pairs of enantiomers often have radically different biological effects.
Chiral resolution methods
There are several methods for achieving chiral resolution. These include:
- Direct crystallization: This is one of the oldest and simplest methods of chiral resolution. It involves the crystallization of a racemic mixture, where the different enantiomers crystallize out of the solution at different rates. This allows them to be separated.
- Chromatography: This method involves passing a racemic mixture through a column filled with a chiral stationary phase. The different enantiomers interact differently with the stationary phase, causing them to travel through the column at different rates and thus be separated.
- Chiral auxiliary: A chiral auxiliary is an optically active substance that is temporarily incorporated into an organic synthesis process to control the stereochemical outcome of the synthesis. In other words, it is used to convert a racemic mixture into a single enantiomer.
- Enzymatic resolution: This method uses enzymes to selectively react with one enantiomer over the other. The unreacted enantiomer can then be recovered from the reaction mixture.
- Chiral pool synthesis: This method involves the synthesis of a desired compound from a starting material that is an enantiomerically pure compound from the "chiral pool", a list of naturally occurring substances with chiral centers.
Importance of chiral resolution
Chiral resolution is particularly important in the pharmaceutical industry, as the different enantiomers of a molecule can have different biological effects. For example, one enantiomer of a drug might have the desired therapeutic effect, while the other enantiomer might be inactive or even harmful. Therefore, it is often necessary to produce drugs in enantiomerically pure form.
Chiral resolution also plays a crucial role in the field of analytical chemistry, where it is used to determine the enantiomeric composition of a sample. In addition, it is used in the field of materials science for the synthesis of chiral materials.