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Optical rotation, also known as ... and generally in chemistry to measure the concentration or enantiomeric ratio of chiral molecules in solution.
Specific rotation is an intensive property, distinguishing it from the more general phenomenon of optical rotation. As such, the observed rotation ( α ) of a sample of a compound can be used to quantify the enantiomeric excess of that compound, provided that the specific rotation ( [α] ) for the enantiopure compound is known.
The ratio, the purity, and the concentration of two enantiomers can be measured via polarimetry. Enantiomers are characterized by their property to rotate the plane of linear polarized light. Therefore, those compounds are called optically active and their property is referred to as optical rotation. Light sources such as a light bulb, Tungsten ...
the specific rotation of (S)-2-ethyl-2-methyl succinic acid is found to be dependent on concentration; in what is known as the Horeau effect [3] the relationship between mole based ee and optical rotation based ee can be non-linear i.d. in the succinic acid example the optical activity at 50% ee is lower than expected.
The observed rotation of the sample is the weighted sum of the optical rotation of each anomer weighted by the amount of that anomer present. Therefore, one can use a polarimeter to measure the rotation of a sample and then calculate the ratio of the two anomers present from the enantiomeric excess, as long as one knows the rotation of each pure anomer.
Chiral drugs that are equimolar (1:1) mixture of enantiomers are called racemic drugs and these are obviously devoid of optical rotation. The most commonly encountered stereogenic unit, [2] that confers chirality to drug molecules are stereogenic center. Stereogenic center can be due to the presence of tetrahedral tetra coordinate atoms (C,N,P ...
In optics, optical rotatory dispersion is the variation of the specific rotation of a medium with respect to the wavelength of light. Usually described by German physicist Paul Drude 's empirical relation: [ 1 ]
For example, in sugar refining, dissolved solids can be accurately estimated from refractive index measurement corrected by an optical rotation (polarization) measurement. [ 10 ] Alcohol has a higher refractive index (1.361) than water (1.333).