Liaison hydrogène O-H-O symétrique: II. Spectres de vibration des oxalates acides de lithium hydratés et anhydres

Abstract

Infrared and Raman spectra of polycrystalline LiHC 2O 4, LiHC 2O 4, · H 2O and their D and 6Li containing isotopic derivatives have been investigated at 300 and 90 K in the 4000–50 cm −1 region. All the internal and external optically active modes of lithium hydrogen oxalate monohydrate have been identified and an assignment is given. The spectroscopic data are consistent with X-ray data showing an asymmetric short hydrogen bond with a positive deuterium isotope effect. The dehydration of LiHC 2O 4, · H 2O changes the type of hydrogen bond which becomes symmetric of the double minimum type. The deuteration of LiHC 2O 4, on the other hand. weakens the hydrogen bond and makes it asymmetric again. The asymmetry appears more pronounced at low temperature.