Optical rotatory dispersion
Encyclopedia
Optical rotatory dispersion is the variation in the optical rotation
of a substance with a change in the wavelength
of light
. Optical rotatory dispersion can be used to find the absolute configuration
of metal complexes.
For example, when plane-polarized white light from an overhead projector is passed through a cylinder of sucrose
solution, a spiral rainbow is observed perpendicular to the cylinder.
When white light passes through a polarizer, the extent of rotation of light depends on its wavelength. Short wavelengths are rotated more than longer wavelengths. Because the wavelength of light determines its color, the variation of color with distance through the tube is observed. This dependence of specific rotation on wavelength is called optical rotatory dispersion.
Optical rotation
Optical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose , solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms...
of a substance with a change in the wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
. Optical rotatory dispersion can be used to find the absolute configuration
Absolute configuration
An absolute configuration in stereochemistry is the spatial arrangement of the atoms of a chiral molecular entity and its stereochemical description e.g. R or S....
of metal complexes.
For example, when plane-polarized white light from an overhead projector is passed through a cylinder of sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
solution, a spiral rainbow is observed perpendicular to the cylinder.
When white light passes through a polarizer, the extent of rotation of light depends on its wavelength. Short wavelengths are rotated more than longer wavelengths. Because the wavelength of light determines its color, the variation of color with distance through the tube is observed. This dependence of specific rotation on wavelength is called optical rotatory dispersion.