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

Abstract

AbstractThe infrared spectra of DMSO/D2O and CH3COOD/D2O were measured under various concentrations and pressure. The frequencies of the C‐H stretching vibration bands for DMSO/D2O mixtures increase with increasing the mole fraction of D2O, implying the contraction of the C‐H bonds. As the pressure was elevated to 1.5 GPa, the C‐H vibrations of DMSO/D2O 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 D2O. Ab initio calculations were performed, while the calculated results are consistent with the interpretations based on the high‐pressure infrared experiments. Analogous to DMSO/D2O, the pressure‐dependent studies on CH3COOD/D2O mixtures provide the evidence of the C‐H—O hydrogen bonding as the pressure was elevated.