Investigations of Raman spectra III-Deuterium-substituted acetic acids

Abstract

Isotopic substitution of deuterium atoms for protium atoms has now been carried out successfully for a widely different variety of substances, and the influence of isotopic substitution on various physical properties has been discussed in the literature. Spectroscopic effects have been investigated in several spectral regions but mostly by Raman effect measurements. Yet in no previous investigation have result been recorded for a substance in which deuterium substitution is made in two parts of the molecule simultaneously or separately. Such substitution is possible in carboxylic acids, and has been effected for the two "heavy" acetic acids whose investigation is reported in this paper. Substitution of deuterium for all protium atoms yielded trideuteracetic deuteracid (CD 3 CO 2 D), and replacement of the carboxyl protium only by deuterium resulted in the formation of acetic deuteracid (CH 3 CO 2 C). Not only do the Raman spectra of these acids differ from the spectrum of acetic acid (CH 3 CO 2 H) due to isotopic effects but, by comparing the three spectra, the actual assignment of the frequencies is rendered easier. In addition, the spectrum of "light" acetic acid has been examined, since there is a marked lack of agreement in existing data, and, for comparison purposes, the spectrum of acetic anhydride has also been investigated.