Cotton effect

Protein structure like beta sheet shows positive Cotton Effect.

It is also possible to perform ultraviolet-visible spectroscopy of stereoisomers by exploiting the Cotton effect.

I have done some research and understand circular dichroism and circular birefringence and their contributions to the "cotton effect".

Ultraviolet-visible spectroscopy (UV-vis) can distinguish between enantiomers by showing a distinct Cotton effect for each isomer.

The Cotton effect is the characteristic change in optical rotatory dispersion and/or circular dichroism in the vicinity of an absorption band of a substance.

The Cotton effect is called positive if the optical rotation first increases as the wavelength decreases (as first observed by Cotton), and negative if the rotation first decreases.

This empirical rule allows the prediction of the sign of the Cotton effect by analysing relative orientation of substituents in three dimensions and in this way the absolute configuration of an enantiomer.

CD is measured under the absorption band of the molecule of interest, while ORD can be measured far from these bands with a "Cotton effect" right underneath the absorption band.

In absorption bands of these substances, he found large variations of optical rotation as a function of wavelength, now known as optical rotatory dispersion (ORD) or as the Cotton effect.