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Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule

Publication ,  Journal Article
Variyar, JE; MacPhail, RA
Published in: The Journal of Physical Chemistry
January 1, 1992

The deuterium-isolated CH stretching band in the isotropic Raman spectrum of gaseous cyclopentane-d9 shows structure associated with the pseudorotation dynamics of the ring. This structure can be reproduced by a theoretical calculation that uses the adiabatic approximation to separate the CH stretching and pseudorotation motions. The uncoupled pseudorotation is modeled as a free one-dimensional rotor, and the CH stretching-pseudorotation coupling is determined from the dependence of the CH stretching frequency on the pseudorotation angle. If this CH stretching-pseudorotation coupling is estimated by assuming a linear correlation between deuterium-isolated CH stretching frequencies and ab initio CH bond lengths, a spectrum with structure much like that of the experimental spectrum is obtained; minor modification of the parameters in this coupling potential yields an excellent fit to the observed spectrum. If the coupling potential is calculated directly from the empirical potential of Lifson and Stern, the comparison with the observed spectrum is poor. Both quantum and classical treatments of the pseudorotation dynamics give similar spectra. In the classical picture, the observed spectrum can be interpreted as the superposition of many CH stretching spectra with varying degrees of motional averaging, each corresponding to cyclopentane-d9 molecules with different amounts of pseudorotational momentum. © 1992 American Chemical Society.

Duke Scholars

Published In

The Journal of Physical Chemistry

DOI

ISSN

0022-3654

Publication Date

January 1, 1992

Volume

96

Issue

2

Start / End Page

576 / 584
 

Citation

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Variyar, J. E., & MacPhail, R. A. (1992). Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule. The Journal of Physical Chemistry, 96(2), 576–584. https://doi.org/10.1021/j100181a016
Variyar, J. E., and R. A. MacPhail. “Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule.” The Journal of Physical Chemistry 96, no. 2 (January 1, 1992): 576–84. https://doi.org/10.1021/j100181a016.
Variyar JE, MacPhail RA. Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule. The Journal of Physical Chemistry. 1992 Jan 1;96(2):576–84.
Variyar, J. E., and R. A. MacPhail. “Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule.” The Journal of Physical Chemistry, vol. 96, no. 2, Jan. 1992, pp. 576–84. Scopus, doi:10.1021/j100181a016.
Variyar JE, MacPhail RA. Pseudorotation and the raman CH stretching spectrum of gaseous cyclopentane-d9: Local modes in a floppy molecule. The Journal of Physical Chemistry. 1992 Jan 1;96(2):576–584.

Published In

The Journal of Physical Chemistry

DOI

ISSN

0022-3654

Publication Date

January 1, 1992

Volume

96

Issue

2

Start / End Page

576 / 584