Structure Of Water In Aqueous Solutions Research Articles

Roles of hydrogen bonding interactions and hydrophobic effects on enhanced water structure in aqueous solutions of amphiphilic organic molecules

Insights into the solute-induced water structural transformations are essential to understand the role of water in biological and chemical reaction processes. Herein, the structural changes in water induced by amphiphilic organic molecules were investigated using concentration-dependent derivative Raman spectroscopy (DRS) combined with two-dimensional Raman correlation spectroscopy (2D Raman-COS). We shall restrict our attention in this work to binary mixtures of water with dimethyl sulfoxide (DMSO), acetone, and isopropanol (IPA), all of which have similar chemical structures. The spectral changes in O:H and OH stretching modes illustrate that the solute molecules induce an enhancement of the water structure in dilute solutions, where the enhanced degree of water structure is closely related to the size of the dipole moment of organic molecules. In addition, the transformations of solute-induced water-specific structures were evaluated by 2D Raman-COS, which shows that the strong hydrogen bond (H-bond) structure of water is more sensitive to organic molecules and induces a transition to the weak H-bond structure of water.

Temperature-Induced Change of Water Structure in Aqueous Solutions of Some Kosmotropic and Chaotropic Salts.

The hydrogen bond structure of water was examined by comparing the temperature dependent OH-stretching bands of water and aqueous NaClO4, KClO4, Na2SO4, and K2SO4 solutions. Results called attention to the role of cations on top of the importance of anions determining the emerging structure of a multi-layered system consisting single water rings or multi-ring water-clusters.

Hydration properties and water structure in aqueous solutions of native and modified cyclodextrins by UV Raman and Brillouin scattering

AbstractWe have studied aqueous solutions of native and chemically modified cyclodextrins (CDs) by means of UV Raman and Brillouin scattering. Analysis of the spectral profile of the OH‐stretching Raman signal, which is sensitive to the intermolecular organization of water, reveals a remarkable reduction of the population of ordered tetrahedral water structures inside the hydration shell of substituted CDs. As a remarkable result, this destructuring effect seems to be mainly related to the number of substituted hydroxyl groups in the CD ring rather than to the chemical nature of the substituent group. UV Brillouin scattering experiments confirm the structural picture emerging from the UV Raman study, also providing an estimate of the activation energy associated to the collective H‐bond restructuring mechanism in CD solutions. Overall, the results provide a coherent description of the water–solute interactions in aqueous solutions of CDs.

INFLUENCE OF HEXAMETHYLPHOSPHOTRIAMIDE MOLECULES ON WATER STRUCTURE

The volume-manometric method was used to measure the solubility of noble gases: helium, argon, and krypton in mixtures of water with HMPA in the region of small additions of the organic component at temperatures of 283.15; 298.15 and 313.15 K. The maximum on the solubility curves is explained by the competing effect of the hydrophobic and hydrophilic hydration of the corresponding fragments of HMPA molecules. The "bond-breaking" model of water was used in the present work. According to this model the possible deformations of the hydrogen bonds are neglected. It makes possible to calculate the fractions of water molecules participating in any number of hydrogen bonds at the specified temperature. The phenomenological model of the structure of HMPA aqueous solutions is presented. On the base of experimental solubility of gases and the permittivity of solutions, it is possible to calculate the structural characteristics of diluted aqueous solutions. In the frame of the model one can determine the contribution of the effects of hydrophobic hydration to the total energy of interactions in the water-non-electrolyte system and describe the changes in water structure in aqueous solutions. It was found that at x = 0.0035 mole fraction of HMPA, there is an increase in the number of water molecules participating in four hydrogen bonds without changing the average number of hydrogen bonds per water molecule. At x = 0.005 the properties of the system are already largely determined by the influence of the polar group (P = O) of the HMPA molecule. At x = 0.0101 additions of the organic component to water lead to the redistribution of H-bonds and have to the same consequences as the increase in temperature from 298.15 to 313.15 K.Forcitation:Zheleznyak N.I. Influence of hexamethylphosphotriamide molecules on water structure. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 36-41

Confinement effects on water structure in membrane lyotropic phases

The change of the water structure in aqueous solutions of the tri-ethyleneglycol mono n-decyl ether (C 10E 3) was studied by micro Raman scattering. The results obtained on the O–H stretching band show that the behavior of the hydrogen bonding (H-bonds) water network can be used as a probe to follow the lamellar (L α) to sponge (L 3) phase transition. In the lamellar phase, the stack of the surfactant molecules aggregated into a two-dimensional structure (membrane) acts as a soft confinement system for the H-bond water network of which the regular tetrahedral structure is perturbed. The change of the planar organization of the membranes to a highly disordered and infinite array of bilayers in the sponge phase amplifies the surface of contact between amphiphilic surfactant and water molecules which drives a strong disruption of the regular tetrahedral H-bonding water network.

Water structure in aqueous solutions of alkali halide salts: FTIR spectroscopy of the OD stretching band

Water structure making/breaking studies in solutions of five alkali halide salts (KF, KI, NaI, CsF and CsCl) in 4 wt% D 2O in H 2O mixtures have been performed by FTIR analysis of the OD stretching band in the full solubility range. The proposed method gives a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in the solution. With the exception of CsCl, there is a very good correlation of the structure making/breaking character of the salts determined by FTIR analysis, and the viscosity coefficients of the solutions. The results fully support and explain previous studies of bubble attachment to microscopic salt particles of the above salts. The investigations support the primary importance of interfacial water structure in the explanation of the flotation of alkali halide salts in their brines.

Raman spectroscopic study of temperature dependence of water structure in aqueous solutions of a poly(oxyethylene) surfactant

The temperature dependence of the water structure in aqueous solutions of a poly(oxyethylene) surfactant C12E5 was examined at concentrations 0, 20, 30, 45, 70 and 90wt% by Raman spectroscopy of the O–H stretching band. The ratio of the intensities of the component around 3200cm−1 (the collective in-phase O–H stretching vibrations of bonded aggregates) to the component around 3400cm−1 (the O–H stretches in which the phase relations are lost) was monitored in the temperature range from 0 to 39°C. The results show that the speed of the thermal destruction of the H-bond network increases as the concentration increases from 0 to 45wt%. This change is attributed to the existence of a substantial amount of water in the system that takes part in the hydrophobic hydration of the poly(oxyethylene) headgroups, despite their predominantly hydrophilic character. The conclusion that this kind of water, which is known to have restricted mobility, plays an important role in the surfactant–water systems is consistent with the high viscosity of the liquid crystalline phases.

Raman Spectroscopic Study of Water Structure in Aqueous Nonionic Surfactant Solutions

Water structure in aqueous solutions of two poly(oxyethylene) surfactants, C12E5 and C12E6, were studied by Raman spectroscopy in the whole range of concentrations. A method based on recording Raman spectra with polarization rotated to 60° with respect to the excitation light was used, allowing one to follow isothermal paths that intersect phases with different polarization properties, viz., the micellar solution phase (isotropic), lamellar phase (anisotropic), and reverse micellar solution phase (isotropic). Besides the O−H stretching band, the conformational bands of the oxyethylene groups were measured to evaluate the dehydration process of the hydrophilic headgroups of the surfactant. The results showed that the behavior of the water structure outlines three main concentration regions, which closely coincide with the three phases intersected by the experimental isotherms. In the micellar solution phase, no significant changes of the water structure are indicated, while, in the lamellar phase, rapid de...

The Study of Water Structure in Aqueous Solutions of Butoxyethanol by Enthalpy of Mixing Measurements

In order to confirm the existence of regions I and II in aqueous solutions of butoxyethanol(BE), the concentration and temperature dependences of enthalpies of mixing of aqueous BE solutions with some organic solvents were measured. It has been found that the increments of apparent enthalpies of mixing per mole of water with respect to the mole fraction of BE change irregularly at a certain concentration. This concentration nearly corresponds to the reported boundary between regions I and II. Although similar behavior has also been observed in aqueous solutions of iso-butoxyethanol, aqueous solutions oftert-butoxyethanol have shown no anomalous behaviors.

Effect of molecular shape and electrostatic interactions on the water layer around polar and apolar groups in solution

We have carried out neutron diffraction using hydrogen/deuterium isotope substitution and molecular dynamics simulations in order to investigate intermolecular water structure in aqueous solutions of phenol, ethanol, propanoic acid, and glucose. Partial radial distribution functions (rdfs) calculated from both experiment and simulation are compared. These show good overall agreement although the simulation gives more structure than the experimental data in the intramolecular region. From the simulation, the relative number of water molecules coordinated to different chemical groups are calculated and the three-dimensional water density around the different chemical groups on the solute molecule is obtained. For both the experimental and simulated rdfs the intermolecular region is relatively featureless but the simulated water structure shows significant differences between the water coordination around polar and apolar groups. The water is strongly coordinated to the polar groups (OH and COO−), although the hydroxyl groups have fewer close waters than would be possible if all hydrogen bonds were satisfied. There is little evidence for stable water networks around apolar groups. There is also some evidence that the polarized regions of the solutes influence the water coordination around neighboring apolar groups. Apart from the relatively strong polar interactions, the overall shape of the solute molecule is the most important determinant of the shape of the hydration shell. In the case of glucose, the OH groups take part in a well-defined hydrogen-bonded network around the glucose molecule which incorporates the solute molecule in a similar way to water molecules.

The measurement of heat capacity differences due to the change of water structure in aqueous solutions of organic compounds

In order to observe more directly the structural organization of water molecules around a non-polar molecule in an aqueous solution, heat capacity differences between two kinds of solutions (solution I and II) of quaternary ammonium salts were measured. In the solution I stable water structure was retained as much as possible and in the solution II water structure was destroyed either by heating to high temperatures or by irradiating with ultrasonic waves. It was found that the heat capacity differences ((Cp)II-(Cp)I) were slightly positive and its maximum values corresponded to 7-8 percent of the heat capacity of pure water itself.

Effect of tetraphenylphosphonium and tetraphenylborate ions on the water structure in aqueous solutions; FTIR studies of HDO spectra

FTIR spectroscopy has been used to study interactions of Ph4B- and Ph4P+ ions with water in aqueous solutions. The effect of Ph4BNa and Ph4PCl on the HDO vibration band in the fundamental region has been investigated. A new modification of the difference spectra method has been applied for the analysis of the spectral data. The results have revealed distinct differences in hydration of Ph4B- and Ph4P+ ions: Ph4B- ion strongly decreases the hydrogen-bond energy of surrounding water molecules, while Ph4P+ ion changes it slightly. The effect of Ph4B- is determined by anion–water interactions, while the effect of Ph4P+ is determined by water–water interactions around the cation. The changes in the energy of water hydrogen bonds upon the ions have been evaluated.

Water structure in aqueous solutions of tetramethylammonium chloride

Neutron diffraction with hydrogen/deuterium isotope substitution is used to investigate the water structure and the solute distribution in aqueous solutions of tetramethylammonium chloride ((CH3)4NCl) between 2.0 and 8.0 m concentrations at room temperature. The hydrogen-hydrogen (HH) pair correlation functions for the water indicate that the hydrogen-bonding geometry is not significantly changed over the concentration range compared to pure water, although the number of hydrogen bonds to nearest-neighbour water molecules decreases with increase in anion concentration. The results show no evidence of increased water structure compared to pure water in either the nearest-neighbour or the longer distance range.

Inferences on dynamic water structure in aqueous solutions from diffusion measurements

The dynamic, hydrogen-bonded structure of water can be profoundly affected by addition of solutes as reflected by the resulting solute—solvent interactions. Measurements of diffusion coefficients for the solute species and for water are a useful probe for studying those interactions and changes in the dynamic water structure. The analysis of transport properties of electrolyte solutions is presently approached both theoretically and experimentally by the use of generalised transport coefficients such as Onsager phenomenological coefficients, velocity correlation coefficients or the closely related distinct diffusion coefficients of Friedman. However, two of these approaches generally use a solvent-fixed frame of reference and thereby exclude the information available from studying the diffusion of the solvent. The velocity correlation coefficient approach is used here to examine hydrogen-bonding effects in binary solution containing water as one component. We discuss also examples where intra-diffusion data for water in aqueous solutions give important insights into the dynamic structure of aqueous solutions.

ChemInform Abstract: ULTRASONIC ABSORPTION MECHANISMS IN AQUEOUS SOLUTIONS OF ALCOHOLS

Chemischer InformationsdienstVolume 6, Issue 44 Article ChemInform Abstract: ULTRASONIC ABSORPTION MECHANISMS IN AQUEOUS SOLUTIONS OF ALCOHOLS SADAKATSU NISHIKAWA, SADAKATSU NISHIKAWASearch for more papers by this authorMITSUO MASHIMA, MITSUO MASHIMASearch for more papers by this authorMICHIO MAEKAWA, MICHIO MAEKAWASearch for more papers by this authorTATSUYA YASUNAGA, TATSUYA YASUNAGASearch for more papers by this author SADAKATSU NISHIKAWA, SADAKATSU NISHIKAWASearch for more papers by this authorMITSUO MASHIMA, MITSUO MASHIMASearch for more papers by this authorMICHIO MAEKAWA, MICHIO MAEKAWASearch for more papers by this authorTATSUYA YASUNAGA, TATSUYA YASUNAGASearch for more papers by this author First published: November 4, 1975 https://doi.org/10.1002/chin.197544078AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume6, Issue44November 4, 1975 RelatedInformation

Ultrasonic Absorption Mechanisms in Aqueous Solutions of Alcohols

Abstract Ultrasonic absorption measurements in aqueous solutions of tert-butyl and allyl alcohols were carried out in the frequency range of 4.5–220 MHz at 25 °C. Two relaxation processes were observed in aqueous solution of tert-butyl alcohol and a single one in that of allyl alcohol. The former relaxation mechanisms were revealed to be due to the perturbation of the equilibria expressed by (Remark: Graphics omitted.) where A and B were alcohol and water molecule respectively. The latter mechanism was due to that expressed by (Remark: Graphics omitted.). The rate constants for all these processes were determined from the concentration dependence of the relaxation frequencies. The water structure in aqueous solutions was discussed in terms of a hydrophobic interaction, and it was concluded that the hydrophobic interaction decreased in this sequence, tert-butyl, n-propyl and allyl alcohols.