ABSTRACT
Chiral molecules exist in two forms that are mirror images of each other, called enantiomers. Pasteur first demonstrated the existence of enantiomers in 1850 when he found the relation between chirality (or molecular dissymmetry as he called it) and optical activity studying sodium ammonium tartrate. Chirality is equivalent to the absence of mirror rotation axes of any order and chiral molecules exhibit the special characteristic that they can rotate the plane of polarization of linearly polarized light. This phenomenon had been discovered in 1812 by Biot and is known as optical rotation. At the origin of optical rotation lies a different refractive index for left-and right-hand circularly polarized light. A second tool to study chiral molecules is known as circular dichroism (discovered in 1895 by Cotton), which is the unequal absorption of left-and right-hand circularly polarized light. Both techniques are intensely used to study chiral molecules and systems.
