Cotton effect

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. In a wavelength region where the light is absorbed, the absolute magnitude of the optical rotation at first varies rapidly with wavelength, crosses zero at absorption maxima and then again varies rapidly with wavelength but in the opposite direction. This phenomenon was discovered in 1895 by the French physicist Aimé Cotton (18691951).

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.[1] A protein structure such as a beta sheet shows a negative Cotton effect.

See also


  1. Ernest L. Eliel and Samuel H. Wilen, "Stereochemistry of Organic Compounds" (Wiley, 1994), p.1000

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.