Intermolecular Hydrogen Bonding Structural Dynamics in Ethylene Glycol by Femtosecond Nonlinear Infrared Spectroscopy

Abstract

In this work, we examined the structural and-OH stretching vibrational dynamics of ethylene glycol (EG) solvated in acetonitrile (MeCN), acetone (AC), tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) using steady-state linear infrared (IR) spectroscopy and ultrafast pump-probe IR spectroscopy. The results suggested that the frequency position, bandwidth, and vibrational relaxation of the-OH stretching vibration that participate in the formation of intermolecular hydrogen bonds (IHBs) were strongly influenced by the type of solvent. At least two types of IHBs were detected in the EG solution including clustered solute-solute IHBs and solute-solvent IHBs. Quantum chemical calculations predicted a similar solvent dependence of the-OH stretching vibrational frequency to that observed in the IR experiments. Furthermore, we found that the IHB-involved-OH stretching mode in the case of solute-solvent clusters displayed the slowest population relaxation dynamics in the case of EG in MeCN. The relaxation became slightly faster in AC and even faster in THF. The fastest dynamics was observed in the case of EG in DMSO. However, in each solvent environment examined, the IHB-involved-OH stretching mode in the solute-solute cluster displayed the fastest population relaxation. The results obtained in this study provide further insights into different IHB structural dynamics in co-existing solute-solute and solutesolvent clusters.

Solvent System with Improved Hydroxide Reactivity for Mild and High-Efficiency PET Alkaline Hydrolysis

“…For a better understanding of the relationship between the hydrogen bonds and the promotion effect on PET degradation, FTIR and the p K a equalization principle were employed in this work. When the −OH group of EG participates in the formation of hydrogen bonds, the O–H bond length is increased leading to a red shift of its IR stretching mode frequency . Therefore, the −OH vibrational frequency reflects the strength of the hydrogen bonds; the larger the red shift, the stronger the hydrogen bonds.…”

“…When the −OH group of EG participates in the formation of hydrogen bonds, the O−H bond length is increased leading to a red shift of its IR stretching mode frequency. 26 Therefore, the −OH vibrational frequency reflects the strength of the hydrogen bonds; the larger the red shift, the stronger the hydrogen bonds. As shown in Figure 4, the positions of -OH stretching vibration absorption peaks of EG in the four cosolvents were gradually shifted toward lower frequencies according to the order from DX, THF, DMI to DMSO.…”