An Overview of the Chiral Separation Mechanisms
Chiral separations have become an important field in separation sciences, since many drugs, agrochemicals, food additives, and fragrances are chiral compounds and their bioactivities are related to their chirality. Many types of molecular chirality are observed. They can be shortlisted into four categories: central chirality; axial chirality; planar chirality; and helical chirality. Modern separations are performed by chromatography whereas spectroscopic techniques, such as nuclear magnetic resonance and x-ray, are useful tools for elucidation of absolute configuration or mechanistic aspects of enantioseparations. The rational design of specific chiral selectors is one of the more challenging problems facing chiral separation. Chiral separation mechanisms are often well explained, and models may offer reliable prediction of the elution orders. The chiral recognition mechanism of circular dichroism is understood fairly well and is based on several phenomena. Polysaccharides such as cellulose and amylose and to a much lesser extent chitin are among the most common naturally occurring chiral polymers.