Intermolecular Interactions in Aqueous Dimethyl Sulphoxide and Acetic Acid Probed by High-Pressure FTIR

摘要

The infrared spectra of DMSO/D_2O and CH_3COOD/D_2O were measured under various concentrations and pressure. The frequencies of the C-H stretching vibration bands for DMSO/D_2O mixtures increase with increasing the mole fraction of D_2O, implying the contraction of the C-H bonds. As the pressure was elevated to 1.5 GPa, the C-H vibrations of DMSO/D_2O were altered into four bands at ～2927 cm~(-1), ～2941 cm~(-1), ～3007 cm~(-1), and ～3025 cm~(-1). Further concentration-dependent studies indicated that the spectral features at ～2941 cm~(-1) and ～3036 cm~(-1) arise from pressure-induced C-H---O hydrogen bonding between C-H in DMSO and oxygen atom in D_2O. Ab initio calculations were performed, while the calculated results are consistent with the interpretations based on the high-pressure infrared experiments. Analogous to DMSO/D_2O, the pressure-dependent studies on CH_3COOD/D_2O mixtures provide the evidence of the C-H---O hydrogen bonding as the pressure was elevated.