INFRARED SPECTRA OF MATRIX-ISOLATED ACETIC ACID MONOMERS
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Date
1970
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Ohio State University
Abstract
Infrared spectra of monomeric acetic acids ($CH_{3}COOH(D)$ and $CD_{3}COOH(D)$) isolated in Ar and $N_{2}$ matrices near $4^\circ K$ have been obtained. A large anharmonic potential energy contribution is evident from the observed isotropic frequency shifts. It is proposed that this arises primarily from the double-minimum potential-energy curve for tunneling of the H atom between O atoms via the COH angle bending coordinate. In all cases important coupling between the COH angle bending and C--O stretching coordinates is observed, with a strong addition of $CD_{3}$ (umbrella) angle deformation in the case of $CD_{3}COOH$. Exceptional matrix effects are observed for the coupled vibrations of the --OH molecules. A complete assignment is proposed for these acetic acids on the basis of the new data. As additional supporting evidence, the spectrum of matrix-isolated $CH_{3}COF$ and of acetic acid vapor at low pressure and long path length are reported.
Description
Author Institution: Department of Chemistry, University of New Hampshire; Department of Chemistry, Texas Technological University