ABSTRACT
This chapter has first defined the phenomena of rotatory polarization and rotatory dispersion. In the first case, the polarization plane (of the studied active substance) has rotated from an angle α after the polarized light has passed through it. In that of rotatory dispersion, it is the change of the value of α with the value of the wavelength of the incident polarized helicoidal light which constitutes the phenomenon. The definition of the Cotton effect is given for this purpose. Rotatory polarization takes place when one of the enantiomers interacts more quickly with one of the circularly polarized light stronger than the other does with the other polarized light. Concerning now the circular dichroism, the polarization waves are not only characterized by different propagation speeds but most often by different absorptions. The origin of the phenomena is briefly tackled in the chapter. It is related to the presence of chromophores in the molecule. Several applications are given in the chapter, in particular in the realm of structural chemistry with examples of some steroids.
