MadSci Network: Chemistry |
You ask a very interesting question. The answer is "No, but..." For ordinary unpolarized light, the index of refraction for a pair of enantioners (no matter how many chiral centers as long as they are truly enantiomers) is the same. Although the index of refraction does change with wavelength, it is the same for the enantiomers for each wavelength. However, it is known that each member of a pair of enantiomers rotates the plane of polarization of plane polarized light, and that they each rotate the plane of polarization in opposite directions to the same amount. The prevailing explanation of this factor is that the plane polarized light can be resolved into equally intense "left" and "right" circularly polarized light components. Plane polarized light can be described as having the electric vector vibrating like a sine wave in only one plane. The magnetic vector comes along as polarized in a plane perpendicular to the plane of the electric vector. One enantiomer interacts both in absorption and refractivity (index of refraction) differently with the two circularly polarized components, and this difference in interaction with the two components is responsible for the optical rotation. Please see; http://www.nsm.buffalo.edu/~jochena/research/opticalactivity.html So the bottom line is one enantiomer does have different indices of refraction for the left" and "right" circularly polarized light components. And the two enantiomers do have different refractive indices for either "right" or "left" circularly polarized light. Dr. Jerry Franzen jtfranzen@fuse.net
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