FORCE CONSTANTS AND FUNDAMENTAL FREQUENCIES OF DIMETHYLDIACETYLENE AND DIACETYLENE
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Date
1951
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Publisher
Ohio State University
Abstract
Redetermination of the depolarization factors of dimethyldiacetylene indicates that the $475 cm^{-1}$ line is depolarized. Using force constants taken from previous work on methylacetylene, methylhaloacetylenes, and dimethylacetylene, it is found that the $475 cm^{-1}$ line should be a bending frequency instead of the central C-C stretching frequency. This stretching frequency falls in the region $450-550 cm^{-1}$ when the central C-C stretching force constant varies from 4-6.5 millidynes/{\AA}. the end C-C stretching frequency lies in the region $950-1150 cm^{-1}$, its value being greatly affected by the value chosen for the central C-C stretching force constant. Additional Raman spectra of liquid dimethyldiacetylene are being taken in order to determine more accurately the location of these two frequencies, since for the spectra obtained from solutions of dimethyldiacetylene only one very weak line was found in each region. Assuming the $644 cm^{-1}$ band of diacetylene is a bending frequency, a reasonable set of force constants for the doubly degenerate vibrations results. The determination of the force constants for the mondegenerate vibrations and the calculated value of the C0-C stretching frequency is in progress for this molecule.
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Author Institution: Illinois Institute of Technology