Determining the Structure of Oxalate Anion Using Infrared and Raman Spectroscopy Coupled with Gaussian Calculations

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• 作者：Karen I. Peterson ; David P. Pullman
• 刊名：Journal of Chemical Education
• 出版年：2016
• 出版时间：June 14, 2016
• 年：2016
• 卷：93
• 期：6
• 页码：1130-1133
• 全文大小：228K
• 年卷期：0
• ISSN：1938-1328

文摘

A laboratory project for the upper-division physical chemistry laboratory is described, and it combines IR and Raman spectroscopies with Gaussian electronic structure calculations to determine the structure of the oxalate anion in solid alkali oxalates and in aqueous solution. The oxalate anion has two limiting structures whose vibrational spectra have distinct differences: planar with D_2h symmetry and nonplanar with D_2d symmetry. In the former case, the IR and Raman spectra are complementary. Students measure the IR and Raman spectra of solid Na₂C₂O₄, K₂C₂O₄, and Cs₂C₂O₄, and a nearly saturated aqueous solution of K₂C₂O₄. They also carry out Gaussian calculations on the oxalate anion to predict the vibrational wavenumbers of both the planar and nonplanar structures and use the results to assign the spectra. By considering their results for the four samples, they decide on the oxalate structure in each and defend their choice in a report. The complexity of the project immerses the students in vibrational spectroscopy so that they learn the subject at a deeper level.