Water Molecules In Aqueous Solutions Research Articles

Determination of the Number of Free Water Molecules in Aqueous Solutions on the Basis of Interrelated Consideration of the Polarization Processes in Water in the THz Frequency Range

Determination of the Number of Free Water Molecules in Aqueous Solutions on the Basis of Interrelated Consideration of the Polarization Processes in Water in the THz Frequency Range

Calculation of the Proportion of Free Water Molecules in Aqueous Solutions Using the Parameters of Their Dielectric Permittivity in the Terahertz Range, Based on the Onsager Theory

The question of the structure of aqueous solutions is one of the most fundamental and complex, while it is relevant to all natural science disciplines. An important parameter of the dynamically equilibrium structure of an aqueous solution is the number of free water molecules. To date, there are no reliable and fully justified methods for determining this parameter. Recently, the terahertz time-domain spectroscopy (THz-TDS) method has been developing. It makes it possible to record the spectra of the complex permittivity in the THz region, where an orientation relaxation band of free water molecules is detected for aqueous solutions. The purpose of this work is to establish the relationship of the parameters of THz dielectric permittivity with the number of free water molecules. For this purpose, the process of polarization of water in the THz region was theoretically considered using the formalism of electrodynamics of continuous media. The Onsager theory is taken as a basis and its development is carried out for the case of high-frequency fields. As a result, an analytical ratio was obtained for calculating the proportion of free water molecules in solutions. A comparison with other well-known, more simplified and poorly substantiated approaches is presented. Calculations of the fraction of free molecules for a number of aqueous solutions have been carried out. It can be argued that the first theoretically justified approach to calculating the population of free water molecules in a solution, which does not contain internal contradictions, is presented.

Structures of 18-crown-6/Cs+ complexes in aqueous solutions by wide angle X-ray scattering and density functional theory

• The oxygen atoms of 18-crown-6 and the hydrogen atoms of water molecule form strong hydrogen bonds in aqueous solution. • Cs + is located directly above the 18-crown-6 ring plane, about 1.15 Å from the centroid of 18-crown-6. • The higher the concentration of CsCl, the lower the complexation percentage of 18-crown-6 to Cs + . • Cs + complexing with 18-crown-6 mainly hydrates with four water molecules. Wide angle X-ray scattering (WAXS) and density functional theory (DFT) were employed to study the structures of aqueous 18-crown-6/CsCl solutions with CsCl concentrations of 0.25, 0.50 and 1.00 mol·L -1 . The empirical potential structure refinement (EPSR) modelling was adopted to get the pair distribution functions (PDFs), coordination numbers ( CN ), coordination number distributions (CND), angle distribution functions (ADFs), independent gradient model (IGM) and spatial density functions (SDFs) for the 18-crown-6 hydration, the complexation of 18-crown-6 and Cs + , the hydration of 18-crown-6/Cs + complex, and the association of Cl - and 18-crown-6/Cs + complex. Judging from the distance and orientation of water molecules, and the IGM between 18-crown-6 and water molecules, the oxygen atoms of 18-crown-6 (Oc) and the hydrogen atoms of water molecules (Hw) form strong hydrogen bonds, and these water molecules were distributed on both sides of the 18-crown-6 ring plane. However, the hydrogen atoms of 18-crown-6 (Hc) hardly form hydrogen bonds with the oxygen atoms of water molecules (Ow). Cs + is located directly above the 18-crown-6 ring plane of 0.35 to 2.05 Å away from the centroid of 18-crown-6, and forms 18-crown-6/Cs + complex with six Oc at r Cs + - O c = 3.06 Å. When the concentrations of CsCl are 0.25, 0.50 and 1.00 mol·L -1 , the complexation percentage of 18-crown-6 to Cs + are about 100%, 58% and 54%, respectively. No classic 2:1 “sandwich” 18-crown-6/Cs + complex structure was found in the solutions we surveyed. Both interaction energies and solvation stability energies reveal that the hydrates of 18-crown-6/Cs + complexes were formed in aqueous solutions. Cs + uncomplexed with 18-crown-6 hydrates with eight water molecules in aqueous solution, while Cs + can also hydrate with about four water molecules when it complexes with 18-crown-6. The results of atomic pair distances, the dipole distance of water molecules, the SDF and the IGM indicate that although water molecules can be located on both sides of the 18-crown-6 ring plane when the hydrates are formed, they hydrate with Cs + on the side where Cs + only existed. Cs + of 18-crown-6/Cs + complex associates with Cl - with the r Cs + - Cl - = 3.79 Å by electrostatic attraction.

Influence of Acidic Environment on Hydrolytic Stability of MDP-Ca Salts with Nanolayered and Amorphous Structures.

PurposeThis study aimed to investigate the hydrolytic stability of 10-methacryloyloxydecyl dihydrogen phosphate calcium (MDP-Ca) salts with nanolayered and amorphous structures in different pH environments.MethodsThe MDP-Ca salts were synthesized from MDP and calcium chloride and characterized by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM). Inductively coupled plasma-mass spectrometry (ICP-MS) was used to quantify the release of calcium from the synthesized MDP-Ca salt, MDP-treated hydroxyapatite (MDP-HAp), and untreated HAp after soaking in acidic and neutral solutions for 1, 7, and 30 days. To study the hydrolytic process, we carried out molecular dynamics (MD) simulations of the nanolayered MCS-MD (monocalcium salt of the MDP dimer) and DCS-MD (dicalcium salt of the MDP dimer) structures, as well as of the amorphous-phase MCS-MM (monocalcium salt of the MDP monomer).ResultsThe TEM images showed that the nanolayered structures were partially degraded by acid attack. Based on the ICP-MS results, the hydrolysis rate of the MDP-Ca salt in acidic and neutral environments followed the order HAp > MDP-HAp > MDP-Ca salt. The MD simulations showed that, in acidic environments, clusters of MDP remained aggregated and all Ca2+ ions separated from the MDP monomer to interact with water molecules in aqueous solution. In neutral environments, Ca2+ ions always interacted with phosphate groups, OH− ions, and water molecules to form clusters centered on Ca2+ ions.ConclusionMDP-Ca presented higher hydrolysis rates in acidic than neutral environments. Nanolayered MCS-MD possessed the highest resistance to acidic hydrolysis, followed by amorphous MCS-MM and DCS-MD.

Peculiarities of structure in aqueous electrolyte solutions and specificity of hydration effects

A new approach to the hydration theory in aqueous solutions of electrolytes is developed. We show that the formation energy of one polarization complex is less than the thermal noise energy, as a result, polarization complexes are not stable. The notion of the effective polarization complex is introduced. It is connected with the concept of contraction of aqueous electrolyte solutions and certifies that the effective hydration number z does not exceed 3÷4. This value agrees with the estimates obtained from the self-diffusion coefficients of ions and water molecules in aqueous solutions of electrolytes. We propose new theories for the kinematic shear viscosity of electrolyte solutions and self-diffusion of ions and water molecules in them. They have nothing in common with the activation approach, with the existence of voids in the water structure and with the quasi-Brownian character of ions displacements. We show that the kinematic shear viscosity is described by the formula which is typical for pure water and other argon-like liquids. The special attention is focused on the determination of a particle radii. The self-diffusion coefficients of water molecules and ions are considered to be the sums of two contributions, one of which has Einstein-like type and another is responsible for the collective drift in the fluctuation hydrodynamic field. We show that values of the self-diffusion and shear viscosity coefficients are inherently consistent with each other.

Stabilizing MXene by Hydration Chemistry in Aqueous Solution

AbstractMXenes attract interest in diverse fields but suffer from fast structural degradation by attacking of dissolved oxygen and water molecules in aqueous solution. This drawback hinders the long‐term storage, applications and understanding of the chemical nature of MXenes. Herein, we report a cost‐effective and environmentally sustainable way for long‐term storage of MXenes in aqueous solution by hydration chemistry of nontoxic inorganic salts. The attacking of MXene by free water and dissolved oxygen molecules is inhibited by decreasing the water activity, which simultaneously lowers the dissolved oxygen concentration, of saline solution. As a result, the storage life of MXene can be prolonged to up to 400 days at ambient conditions without loss of intrinsic surface chemistry and bulk carrier properties. Over 90 % of salt protectant can be recycled by simply evaporating the final waste liquor after fully extracting the MXene to minimize the waste discharge and processing cost. This work offers a commercializable approach with high cost‐effectiveness, processing sustainability and environmental benefit for extending the shelf life of MXenes.

Stabilizing MXene by Hydration Chemistry in Aqueous Solution.

MXenes attract interest in diverse fields but suffer from fast structural degradation by attacking of dissolved oxygen and water molecules in aqueous solution. This drawback hinders the long-term storage, applications and understanding of the chemical nature of MXenes. Herein, we report a cost-effective and environmentally sustainable way for long-term storage of MXenes in aqueous solution by hydration chemistry of nontoxic inorganic salts. The attacking of MXene by free water and dissolved oxygen molecules is inhibited by decreasing the water activity, which simultaneously lowers the dissolved oxygen concentration, of saline solution. As a result, the storage life of MXene can be prolonged to up to 400 days at ambient conditions without loss of intrinsic surface chemistry and bulk carrier properties. Over 90 % of salt protectant can be recycled by simply evaporating the final waste liquor after fully extracting the MXene to minimize the waste discharge and processing cost. This work offers a commercializable approach with high cost-effectiveness, processing sustainability and environmental benefit for extending the shelf life of MXenes.

Hydrogen Complexes of 1,2-Naphthoquinone with Water Molecules in Aqueous Solution and Their Influence on Shifts of Absorption Bands

Hydrogen Complexes of 1,2-Naphthoquinone with Water Molecules in Aqueous Solution and Their Influence on Shifts of Absorption Bands

Molecular Mechanism of Acceleration and Retardation of Collective Orientation Relaxation of Water Molecules in Aqueous Solutions.

The collective orientation relaxation (COR) of water molecules in aqueous solutions is faster or slower with an increase in the concentration of the solutions than that in pure water; for example, acceleration (deceleration) of the COR is observed in a solution of sodium chloride (tetramethylammonium chloride) with increasing concentration. However, the molecular mechanism of the solution and concentration dependence of the relaxation time of the COR has not yet been clarified. We theoretically investigate the concentration dependence of the COR of water molecules in solutions of tetramethylammonium chloride (TMACl), guanidinium chloride (GdmCl), and sodium chloride (NaCl). Based on the Mori-Zwanzig equation, we identify two opposing factors that determine the COR of water molecules in any aqueous solution: the correlation of dipole moments and the single-molecule orientation relaxation. We reveal the molecular mechanism of the concentration dependence of the relaxation time of the COR in the TMACl, GdmCl, and NaCl solutions in terms of these two factors.

Characterization of Aqueous Lower-Polarity Solvation Shells Around Amphiphilic 2,2,6,6-Tetramethylpiperidine-1-oxyl Radicals in Water.

Solvation of the amphiphilic nitroxide radical 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and hydrophilic 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPONE) in water and tetrahydrofuran (THF) is studied in detail. The existence of pure water shells enclosing TEMPO in an aqueous solution that leads to significantly reduced local polarity at the nitroxide moiety is shown with multifrequency electron paramagnetic resonance (EPR) spectroscopy at X- and Q-bands as well as spectral simulations. These aqueous lower-polarity solvation shells (ALPSS) offer TEMPO a local polarity that is similar to that in organic solvents like THF. Furthermore, using double electron-electron resonance spectroscopy, local enrichment and inhomogeneous distribution without direct molecular encounters of dissolved TEMPO in water are found that can be correlated with potentially attractive interactions mediated through ALPSS. However, no local enrichment of TEMPO is found in organic solvents such as THF. In contrast to TEMPO, the structurally very similar nitroxide radical TEMPONE shows no ALPSS encapsulation behavior with water molecules in aqueous solutions. Ensemble-averaging methods such as dynamic light scattering and electrospray ionization mass spectrometry substantiate the EPR spectroscopically obtained results of ALPSS-encased TEMPO and attractive interactions between them, leading to a higher local concentration. Furthermore, force field molecular dynamics simulations and metadynamics deliver support for our conclusions.

Effect of cation substituent of dodecanesulfate-based anionic surface active ionic liquids on micellization: Experimental and theoretical studies

Anionic surface active ionic liquid (SAIL), 1-butyl-3-ethoxycarbonylimidazolium dodecanesulfate ([Etbim][C12H25SO4]) was synthesized. The dependence of micellization of dodecanesulfate-based anionic SAILs on cation substituents of anionic SAILs was analyzed using experimental and theoretical studies. Critical micelle concentration of [Etbim][C12H25SO4] was 1.17 mmol/L at 298.15 K. [Etbim][C12H25SO4] showed superior surface property than [Bmim][C12H25SO4] with same dodecanesulfate anion.Theoretical density functional theory (DFT) calculation was used to determine the micellization tendency of anionic SAILs ([Bmim][C12H25SO4] and [Etbim][C12H25SO4]). CMC difference of [Etbim][C12H25SO4] and [Bmim][C12H25SO4] was ascribed to the electrostatic interaction (repulsion or attraction) and hydrophobic interaction of cations ([Bmim]+ and [Etbim]+), dodecanesulfate anion, anionic SAILs ([Bmim][C12H25SO4] or [Etbim][C12H25SO4]), and the interactions toward water molecules in aqueous solution. The hydrocarbon chain lengths of [Bmim]+ and [Etbim]+ reflected the different hydrophobic interaction of cations, which clarified that the important role of cation substituents on micellization of [Etbim][C12H25SO4] and [Bmim][C12H25SO4]. Atomic charge distribution of cations will play important role on the further hydration toward water molecules or electrostatic attraction toward [C12H25SO4]− anion. Typical hydrogen bonds and charge changes of typical atoms were beneficial for electrostatic attraction and electrostatic repulsion between polar groups of SAILs. The electrostatic repulsion and electrostatic attraction between polar groups of SAILs affected the CMC values of [Bmim][C12H25SO4] and [Etbim][C12H25SO4]. Changes of binding energy (D0) and difference of binding energy (ΔD0) confirmed the tendency of [Etbim][C12H25SO4] micelle formation was higher than that of [Bmim][C12H25SO4].

Dynamical and Structural Properties of Water in Silica Nanoconfinement: Impact of Pore Size, Ion Nature, and Electrolyte Concentration.

In this study, we characterized the structure and the dynamics at a picosecond scale of water molecules in aqueous solutions with cations having various kosmotropic properties (XCl2 where X = Ba2+, Ca2+, and Mg2+) confined in highly ordered mesoporous silica (MCM-41 and grafted MCM-41) by Fourier transform infrared spectroscopy and quasi-elastic neutron scattering. We pinpointed the critical pore size and the electrolyte concentration at which the influence of the ion nature becomes the main factor affecting the water properties. These results suggest that whatever the ions kosmotropic properties, for pore sizes ϕp < 2.6 nm and [XCl2] ≤ 1 M, the water dynamics is mainly slowed down by the size of the confinement. For pore sizes of 6.6 nm, the water dynamics depends on the concentration and kosmotropic properties of the ion more than on the confinement. The water properties within the interfacial layer were also assessed and related to the surface ion excesses obtained by sorption isotherms. We showed that, for pore sizes ϕp ≥ 2.6 nm, the surface ion excess at the pore surface is the main driver affecting the structural properties of water molecules and their dynamics within the interfacial layer.

Encapsulation versus Self-Aggregation toward Highly Selective Artificial K+ Channels.

Natural ion-channel proteins allow ion transport across cell membranes at rates very close to those for ionic diffusion in water. Among them, naturalKcsA K+ channels present high transport rates and total selectivity for K+ cations, rejecting all other cations. Most of the reported artificial ion channels cannot reach this type of activity because of their low selectivity. Several synthetic channels have been designed to mimic the natural KcSA channels, but those presenting an important K+/Na+ selectivity are limited. High-selectivity issues are determinant for the performance of natural protein channels, but they have been not considered as determinant in controlling the transport activity of the artificial ion channels. This Account discusses the last developments of artificial supramolecular carriers or channels that selectivelytransport K+ cations against other cations. Mimicking the complex structures of protein channels is an important research area. These studies are related to such adaptive biomimetic systems that can self-select their functions, with a specific emphasis on artificial superstructures enabling K+ transport like in the natural ones. Alternatively, it is more than interesting to synthetically construct only the active key structures of protein filters or gates that give the chemical selectivity or lead us to describe their dynamic role in the ion pumping and translocation along the channel. Several self-assembled macrocyclic channels are presented here. The macrocyclic binding sites may selectively encapsulate the K+ cations or form aggregated H-bonded central pores of self-assembled macrocycles that coordinate the K+ cations as hydrating water molecules in aqueous solution, compensating for the energetic cost of cation dehydration. These macrocyclic channels are responsive in the presence of K+ cations, even when a large excess of Na+ is present. From the mechanistic point of view, these systems express a synergistic dynamic feature: addition of K+ cations drives the selection and emergence of specific ion channels that selectively conduct the K+ cations that promoted the formation of channel superstructures in the first place. These highly permeable and K+-selective artificial channels may be considered as simple primitive biomimetic alternatives of natural KcsA channels that may find interesting applications in chemical separations, selective sensing, and biomedical materials.

Ab Initio Simulations of Water Dynamics in Aqueous TMAO Solutions: Temperature and Concentration Effects.

We use ab initio molecular dynamics simulation to study the effect of hydrophobic groups on the dynamics of water molecules in aqueous solutions of trimethylamine N-oxide (TMAO). We show that hydrophobic groups induce a moderate (<2-fold) slowdown of water reorientation and hydrogen-bond dynamics in dilute solutions, but that this slowdown rapidly increases with solute concentration. In addition, the slowdown factor is found to vary very little with temperature, thus suggesting an entropic origin. All of these results are in quantitative agreement with prior classical molecular dynamics simulations and with the previously suggested excluded-volume model. The hydrophilic TMAO headgroup is found to affect water dynamics more strongly than the hydrophobic moiety, and the magnitude of this slowdown is very sensitive to the strength of the water-solute hydrogen-bond.

Primary Formation Path of Formaldehyde in Hydrothermal Vents.

Formaldehyde is abundant in the universe and one of the fundamental molecules for life. Hydrothermal vents produce a substantial amount of hydrogen molecules by serpentinization and promote reductive reactions of single carbon compounds. The abundance of formaldehyde is expected to be low due to the high Gibbs free energy in hydrothermal vents. We consider two competing formation pathways of formaldehyde: (1) the reduction of CO by H2 and (2) the reduction of HCOOH by H2 to form a methanediol, followed by the dehydration of the methanediol. We performed a number of quantum chemical simulations to examine the formation of formaldehyde in the gas phase as well as in aqueous solution. The energy barrier is significantly reduced by the catalytic effect of water molecules in aqueous solution and becomes lowest when a water cluster consisted of 5 water molecules catalyzes the reduction. The energy barrier to form a methanediol by the reduction of HCOOH is lower by 17.5 kcal/mol than that to form a formaldehyde by the reduction of CO. Considering the low energy barrier to dehydrate methanediol, the primary pathway to form formaldehyde in hydrothermal vents is concluded to be the reduction of HCOOH by H2, followed by the dehydration of methanediol.

A root bond between ice and antifreeze protein

It has always been assumed that a three-dimensional protein structure is essential to antifreeze protein (AFP) ice interactions. Using a 9 kDa AFP isolated from the springtail, Gomphiocephalus hodgsoni, it was found that the bond between ice and protein is maintained independent of higher order protein structure. GomplyAFP9 remained bound to ice after denaturing by a range of agents (boiling, extreme pH, DTT, ethanol, urea). Thermal hysteresis was minimal (0.03–0.04 °C), but not lost. Crystal faceting and growth occurred normal to the c-axis, indicating the protein binds primarily to sites along the a-axis. These observations lend additional support to the hypothesis of irreversible binding. More significantly, they suggest that binding to ice and functional hysteresis may be achieved independently (i.e. are different operations). These results are consistent with the view that there is a root bond with ice and it is achieved via an amino acid derived interface that bonds to water molecules in aqueous solutions.

"Hydration Shells" of CH2 Groups of ω-Amino Acids as Studied by Deuteron NMR Relaxation.

Hydration phenomena play a very important role in various processes, in particular in biological systems. Water molecules in aqueous solutions of organic compounds can be distributed among the following substructures: (i) hydration shells of hydrophilic functional groups of molecules, (ii) water in the environment of nonpolar moieties, and (iii) bulk water. Up to now, the values of hydration parameters suggested for the description of various solutions of organic compounds were not thoroughly analyzed in the aspect of the consideration of the total molecular composition. The temperature and concentration dependences of relaxation rates of water deuterons were studied in a wide range of concentration and temperature in aqueous (D2O) solutions of a set of ω-amino acids. Assuming the coordination number of the CH2 group equal to 7, which was determined from quantum-chemical calculations, it was found that the rotational correlation times of water molecules near the methylene group is 1.5-2 times greater than one for pure water. The average rotational mobility of water molecules in the hydration shells of hydrophilic groups of ω-amino acids is a bit slower than that in pure solvent at temperatures higher that 60 °C, but at lower temperatures, it is 0.8-1.0 of values of correlation times for bulk water. The technique suggested provides the basis for the characterization of different hydrophobic and hydrophilic species in the convenient terms of the rotational correlation times for the nearest water molecules.

Dangling OH Vibrations of Water Molecules in Aqueous Solutions of Aprotic Polar Compounds Observed in the Near-Infrared Regime.

Near-infrared (NIR) absorption spectrum measurements over a frequency range from 4000 to 12000 cm(-1) were employed to investigate the effects of the presence of solute compounds to vibrational modes of water molecules in aqueous solutions of some aprotic hydroneutral polar compounds with large dipole moments, such as nitro compounds and nitriles. The obtained NIR spectra for the aqueous solutions were decomposed into three components: free water, solute, and water molecules affected by the presence of solutes. Newly determined NIR spectra of affected water molecules were well-described with at least four absorption modes observed at 7040, 6850, 6450, and 5640 cm(-1) for both the nitro compounds and nitriles. The highest frequency mode at 7040 cm(-1) possessing the strongest intensity was assigned to the first stretching overtone of affected water hydroxy (O-H) groups, which are nonhydrogen bonded to other water molecules and dangling. The second highest frequency mode at 6850 cm(-1) was assigned to the first stretching overtone of affected water O-H groups hydrated to other (free) water molecules. The third mode at 6400 cm(-1) was attributed to a combination mode of the fundamental stretching of O-H and the first overtone of the O-H bending mode of the affected water molecules. The lowest frequency mode at 5640 cm(-1) was assigned to the combination mode of the fundamental O-H stretching mode, the fundamental O-H bending mode, and the hindered rotational (libration) mode of the affected water molecules. Because absorption intensities of the third and lowest frequency modes for water molecules affected by the solutes depended on the sizes of alkyl groups of polar solutes, these two modes possibly result from the contribution of hydrophobic hydration effects.

Theoretical study of decomposition of methanediol in aqueous solution.

Methanediol is a product of the hydration of formaldehyde and is more abundant than formaldehyde in aqueous solution. We carried out a number of quantum chemical simulations to study the decomposition of methanediol in aqueous solution. The decomposition of a methanediol proceeds by transferring a proton from a hydroxyl to an oxygen atom of the other hydroxyl in the methanediol. The decomposition of the methanediol completes after the cleavage of the bond between the formaldehyde and the water molecule. The probability of the proton transfer increases by the quantum mechanical tunneling at the low temperature because the width of the potential barrier for the decomposition becomes similar to the de Broglie wavelength of the proton. We consider the catalytic effect of water molecules in aqueous solution. The structure of the methanediol is not required to change significantly when undergoing decomposition due to the active role of water molecules to transfer a proton. We consider three types of arrangement for water molecules with respect to a methanediol: (1) a ring structure formed by a methanediol and water molecules; (2) a water cluster attracted to a methanediol by hydrogen bonds; and (3) a water cluster and additional water molecules, both of which are attracted to a methanediol by hydrogen bonds. The activation energy for the decomposition is reduced by a water cluster more efficiently than water molecules in a ring structure. However, the activation energy reduced by a water cluster is still larger than that obtained from laboratory experiments. We include water molecules that are attracted to a methanediol by hydrogen bonds during the water-cluster-catalyzed decomposition of a methanediol. The hydrogen bonds with the water molecules permit little change in the structure of the methanediol during the decomposition and play a significant role to reduce the activation energy for the decomposition. The rate constant obtained from the theoretical simulation agrees well with that determined by the laboratory experiment.

Ultrasonic, DFT and FT-IR studies on hydrogen bonding interactions in aqueous solutions of diethylene glycol

The density, viscosity and ultrasonic velocity measurements were carried out in aqueous diethylene glycol (DEG) solutions at different concentrations and temperatures to illustrate the hydrogen bonding interactions of DEG with water. The main acoustic parameters such as isentropic compressibility (βs), acoustic impedance (Z), hydration number (Hn), intermolecular free length (Lf), classical sound absorption (α/f2)class and shear relaxation time (τ) were calculated based on the experimentally measured values. These parameters have been utilized to study the solute–solvent interactions in aqueous DEG solutions. Further, these results suggest that the clusters of likely complex DEG molecule form hydrogen bonding with five water molecules in aqueous solution. The quantum chemical calculations were also performed to study the hydrogen bonding interactions between DEG in g−g+t–tg−t conformation and five water molecules. Computations have been done by DFT method at B3LYP/6-311+g(d,p) level of theory to study the equilibrium structure of DEG monomer in gas phase, DEG–(water)5 interacting complex in gas and solvation phases and the vibrational frequency shift due to formation of intermolecular hydrogen bonding. The solvation phase study was carried out using Onsager's reaction field model in water solvent. The computed and scaled vibrational frequencies are in good agreement with the main features of the experimental spectrum when five water molecules are considered explicitly with DEG in g−g+t–tg−t conformation. The parameters such as optimization energy (Etotal), hydrogen bond length and dipole moment (μm) of the interacting complex are also presented and discussed within the light of solute–solvent interactions.