Raman spectra and structure of hydrogen‐bonded water oligomers in tetrahydrofuran–H₂O binary solutions

Abstract

Raman spectra of hydrogen-bonded water oligomers have been resolved from concentration-dependent Raman spectra of tetrahydrofuran (THF)-water binary solutions with the use of multivariate curve resolution with alternating least-squares (MCR-ALS) analysis, assisted by hypothetical addition multivariate analysis with numerical differentiation (HAMAND) procedure. A total of 38 Raman spectra acquired in the broad spectral range of 700-3810 cm À1 were analyzed in a multistep procedure to explain the spectral variations in terms of four components: pure THF, Spectra A, Spectra B, and Spectra C. A fourcomponent MCR-ALS analysis was performed with initial guesses by HAMAND analysis to refine the spectral components and determine their concentration dependence. Of the MCR-ALS resolved three spectra, A was identified as THF(H 2 O), B as THF(H 2 O) 2 with two hydrogens attached to THF, and C as THF(H 2 O) n having two or more linearly hydrogen-bonded oligomers of water (n = 2-4). Observed spectral changes of the OH stretch vibrations of water and those of the C-C/C-O stretches of THF were well reproduced by quantum chemical calculations. Formation of hydrogen-bonded water oligomers in THF-water complexes has thus been revealed. The present study provides a new insight into the basics of hydrogen bonding formation in aqueous systems. It also provides experimental methodology for extracting concentration-dependent minor spectral components contained in complex condensed-phase Raman spectra.

Can Aluminum Cations Promote Nucleation for THF Hydrate Growth?

“…The presence of THF leads to hydrogen bonding of THF with water molecules. 28 Many salts readily dissociate into ions when dissolved in aqueous solutions. The addition of salt introduces the "ion−water" interaction.…”

“…The interaction between water molecules is through hydrogen bonding because oxygen is an electronegative atom. The presence of THF leads to hydrogen bonding of THF with water molecules . Many salts readily dissociate into ions when dissolved in aqueous solutions.…”

Unprecedented Bonding Dynamics during THF and DMSO Molecular Hydration

“…The intensities of the intra-solute C-C/C-O and S-C/S=O bonding vibrations increase as the concentration of organics increases. 27,28 To trace the relaxation of the dominate HB in the organicwater mixtures, it would suffice for one to focus on the H-O stretching vibration at 3000-3700 and However, one can hardly resolve how the individual bond of the hydrating system relaxes upon increasing the solute/solvent concentration from the full-frequency Raman spectra. The PDPS is proven one of the most efficient means for distilling relaxation information of the individual type of bonds in responding to a load of perturbation.…”

Editorial on the special issue of JRS on vibrational spectroscopy of water

“…Gerasimova et al [ 7 ] studied the phase transition of hexahydrate fluoride using Raman spectroscopy with H/D exchange. Raj et al [ 8 ] investigated tetrahydrofuran‐water binary solutions using the cutting‐edge Raman MCR technique. Saha et al [ 9 ] reviewed Raman spectroscopic studies of water in ionic liquids, focusing on interaction between water and ionic species at the molecular level.…”