VIBRATIONAL CIRCULAR DICHOROSISM AS A CRITERION FOR LOCAL MODE VERSUS NORMAL MODE BEHAVIOR
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Date
1986
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Ohio State University
Abstract
The local mode approach frequently permits a straight forward and appealing interpretation of near infrared and visible vibrational spectra of the higher ovetoones of organic $molecules.^{(1)}$ Vibrational circular dichroism (VCD) spectra have the potential to distinguish radily between local mode and normal mode behavior. This is so because the kinetic and potential energy coulings that lead to normal mode behavior are frequentuly crucial for the generation of significant VCD intensity. To test this concept, we have undertaken a VCD study in the spectral region 1000-800 mm of terpenes and related molecules. The molecules are of the sort whose VCD spectra have been studied extensively in the CH-stretching fundamental region by Laux $et al. ^{(2)}$ The concept seems ti be a sueful one. For example, we find that (R)-(+)-limonene and its enantiomer exhibit circular dichroism for the thrid overtone that can be attributed to normal modes of the sort discussed in reference 2: on the other hand, we can detect no VCD intensity in the analogous transition of (-)-menthone.
Description
$^{1}$ B. R. Henery, in ``Vibrational Spectra and Structural,'' J. R. Durig, Ed.; Elsevier; New York, 1981; Vol. 10. $^{2}$ L. Laux, V. M. Pultz, S. Abbate, H. A. Havel, J. Overend. A. Foscowitz and D. A. Lightner. J. Am. Soc. 104, 4276 (1982). Address of Abbate: Istituto di Chimica delle Macromolecole, C. N . R. Milano, Italy. Address of Longhi : Dipartimento di Chimica Industriale, Politecnico, Milano, Italy. Address of Richard: Laboratoire de Spectroscopie Infrarouge, Bordeaux, France. Address Bertucci, Rosini and Salvadori: Centro Studi C. N. R., delle Molecole stereoordinate e otticamente attive. Pisa, Italy. Address of Moscowitz: Chemistry Department, University of Minnesota, Minneapolis 55455, Minnesota.
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