Raman Scattering Spectra and DFT Computational Analyzes of Intermolecular Interactions in Trifluoroacetic and Its Solutions

In this work, the mechanisms of molecular clusters formation in liquid trifluoroacetic acid were studied using Raman scattering spectra in different solutions. The polarized components of Raman scattering spectra corresponding of the C=O, O–H stretching bands of pure trifluoroacetic acid consist of three broad bands at 1734, 1754, and 1800 cm−1 with different depolarization ratios. When the acid is strongly dissolved in acetonitrile, the 1800 cm−1 spectral band belonging to the C=O band remains. The intermolecular interactions in the formation of trifluoroacetic acid monomer, dimer, and trimer, as well as clusters with water [CF3COOH + (H2O)n, n = 1–7] and acetonitrile [CF3COOH + (CH3CN)n, n = 1–2] molecules, were analysed using the density functional theory (DFT) method.