Water Structure Breaker Research Articles

Volumetric properties of a nonionic microemulsion

A model nonionic microemulsion system was studied by dilatometric methods as a function of temperature (15–30°C) and volume fraction of dispersed phase, W 2 (0.2–0.01). From these measurements the partial specific volume, v 2 , of the dispersed phase was derived, and the results were extrapolated to infinite dilution to give v 2 0 . It was found that v 2 was linear with W 2; no breaks were evident, indicating that the microemulsion is “dilutable.” A plot of v 2 0 against temperature was slightly concave down, indicating that the microemulsion surface was a water structure breaker, as expected for a polyethylene oxide covering. The excess volume V E and partial excess volume ∂ v E /∂W 2 were also determined. Since V E was significantly different from zero, ideal mixing did not hold. The partial excess volume extrapolated to infinite dilution was found to be about −0.042 ml g −1, which is also comparable to that found for polyethylene oxide, about −0.048 g −1. The volume decrease on mixing for the microemulsion with the (nominal) value of 0.10 was found to be about 40 × 10 −4 ml g −1, indicating that the microemulsion composition is closer to a lower critical solution temperature.

Participation of water in conformational change of isotactic poly(2‐hydroxyethyl methacrylate) as studied by viscometry in various electrolytic solutions

AbstractConformational properties of isotactic poly(2‐hydroxyethyl methacrylate) (PHEMA) have been studied by viscometry in various electrolytic solutions. The intrinsic viscosity of isotactic PHEMA at 0.01M salt solution increases with decreasing the B coefficient in Jones—Dole's equation. In respective to water structures, a polymer chain is more expanded in the salt solution including water structure breaker ions. As the concentration of ions increases, the interactions between polymer segments and ions make a major contribution to conformational changes of isotactic PHEMA. Depending on the kind of ions, a salting‐in or out effect is observed at higher concentrations than 0.1M salt solution. We observed that the denaturing effects of various anions in isotactic PHEMA salt solutions are as follows; SO42‐ < F− < I− NO3− < SCN‐. This order is similar to the Hofmeister series. To investigate the influences of denaturing agents on solvent structures, we also compared the guanidine hydrochloride effect with the tetrabutylammonium chloride effect in isotactic PHEMA solution.

Solubilities of boric acid in heavy water.

A gravimetric analysis using meta-boric acid (HBO2 or DBO2) as a weighing form has been developed for solubility measurement. The method gave satisfactory results in preliminary measurement of solubilities of boric acid in light water. By using this method, the solubilities of 10B enriched D3 BO3 in heavy water were measured. The results are as follows; 2.67 (7°C), 3.52 (15°C), 5.70 (30°C), 8.87 (50°C) and 12.92 (70°C) w/o, respectively. These values are about 10% lower than those in light water. Thermodynamical consideration based on the data shows that boric acid is the water structure breaker.

Solubilities of Boric Acid in Heavy Water

A gravimetric analysis using meta-boric acid (HBO2 or DBO2) as a weighing form has been developed for solubility measurement. The method gave satisfactory results in preliminary measurement of solubilities of boric acid in light water. By using this method, the solubilities of 10B enriched D3 BO3 in heavy water were measured. The results are as follows; 2.67 (7°C), 3.52 (15°C), 5.70 (30°C), 8.87 (50°C) and 12.92 (70°C) w/o, respectively. These values are about 10% lower than those in light water. Thermodynamical consideration based on the data shows that boric acid is the water structure breaker.

Change of water structure by solvents and polymers Part 4: Albumin-water solutions with acetylsalicylic, hydrochloric and ascorbic acid, lysine- and ammonium chloride and with dextrane and sorbit

Viscosity measurements were made in the temperature range of 10 °–40 °C. The equationν=ν o exp(B/(T-T o )) was used with the parameterT 0 as “structure indicator”, which is called the “limiting temperature”. For instance, hydrocarbons, as liquids with “quasifree” molecules, haveT 0=O; water as a highly structured liquid hasT 0= 140–150 K. The polymer investigated was ovalbumin in aqueous solution in a concentration comparable to that of blood. Acetylsalicylic acid produces a protein conformation which breaks the water structure in solution at a pH of within the in vivo region. The question of whether only the acidity determines the water structure breaking properties of the protein is investigated by acidifying albumin-water solutions with hydrochloric acid, lysine chloride and ascorbic acid. All these acids exhibit similar effects. A stronger influence is observed for ammonium chloride. Its interaction with ovalbumin produces a strong structure-breaking effect. The most powerful water structure breaker in albumin-water solutions is dextrane. In a concentration of 10 % it changes the polymer conformation so that the water structure is broken to such an extent that the solution behaves as an almost “quasifree” liquid withT 0=O.

Thermodynamic Study on Solvent Extraction of 18-Crown-6–Alkali Metal Ion Complexes and Tetraalkylammonium Ions with Picrate Anions into Benzene

Abstract Enthalpy and entropy changes for ion-pair extractions of tetraalkylammonium ions (Me4N+, Et4N+, n-Pr4N+, n-Bu4N+) with picrate anions, overall extractions of alkali metal (Na, K, Rb, Cs) picrates with 18-crown-6 (18C6), and distribution of 18C6 itself were determined between benzene and water, Me, Et, n-Pr, and n-Bu denoting methyl, ethyl, propyl, and butyl groups, respectively. All the extracted 18C6 complexes were 1:1:1 complexes (alkali metal ion: 18C6: picrate anion). The values of enthalpy and entropy changes are negative for overall extractions of all the alkali metal picrates with 18C6. Plots of thermodynamic quantities for ion-pair extractions of R4NA vs. the number of carbon atoms of R4N+ show a linear relationship, R4N+ and A− being tetraalkylammonium ion and picrate anion, respectively. Enthalpy and entropy changes were calculated for ion-pair extractions of 18C6–alkali metal ion complexes with picrate anions. The thermodynamic parameters for ion-pair extractions of 18C6–alkali metal picrate complexes were compared with those of R4NA, and were discussed in detail from the standpoint of molecular grounds. It was found from these data that the 18C6–K+ complex acts as a structure breaker in water.

Relation between molecular size and diffusivity for acid dyes, disperse dyes and their model compounds in aqueous solution.

In order to estimate the diffusivities of dyes (D) in water from their molecular size (MS), the relation between MS and D were examined for acid dyes, non-ionic azo dyes, sulfonic acids, carboxylic acids, alcohols, sugars, amides, ureas, cycloalkanes and benzene derivatives. The molar volume (Vb) at normal boiling point, the van der Waals volume (Vw) and the limiting partial volume (V°) in water were used as measures of the MS.A detailed inspection of the log (Vw, Vb or V°) vs. log (T/Dη) plots results in the following statements, where T is absolute temperature and η is viscosity of water.i) Plots of log Vb or log Vw vs. log (T/Dη) yield straight lines for solutes of a homologous series. The corresponding regression lines render possible an estimation of consistent D value of the respective solute.ii) The Stokes-Einstein equation is unsuited to correlate the parameters characterizing the MS with the diffusion coefficients D of the solutes inspected.iii) The diffusivity of the dyes in water depends on both the solute size and the effect of the solutes on water structure. The values of D for sodium disulfonates with small hydrophobic moiety are far greater than those estimated by the Wilke-Chang's equation, while the values of D for carboxylate anions are smaller than those estimated by Wilke-Chang's. This fact was explained on the facts that carboxylates and sulfonic acid groups act as water structure makers and breakers, respectively.

The systematic characterization by aqueous column chromatography of solutes which affect protein stability.

We have systematically characterized, by aqueous column chromatography on a size exclusion cross-linked dextran gel (Sephadex G-10), 12 solutes, 11 of which are known to affect protein stability. Six are chaotropes (water structure breakers) and destabilize proteins, while five are polar kosmotropes (polar water structure makers) and stabilize proteins. Analysis of the chromatographic behavior of these neutral (ethylene glycol, urea), positively charged (Tris, guanidine, as the hydrochloride salts) and negatively charged (SO2-4, HPO2-4, F-, Cl-, Br-, Cl3CCO-2, I-, SCN-, as the sodium salts, in order of elution) solutes at pH 7 as a function of sample concentration (up to 0.6 M), supporting electrolyte, and temperature yields four conclusions, based largely on the behavior of the anions. Chaotropes adsorb to the gel according to their position in the Hofmeister series, with the most chaotropic species adsorbing most strongly. ++Chaotropes adsorb to the gel less strongly in the presence of chaotropes (a salting in effect) and more strongly in the presence of polar kosmotropes (a salting out effect). Polar kosmotropes do not adsorb to the gel, and are sieved through the gel according to their position in the Hofmeister series, with the most kosmotropic species having the largest relative hydrodynamic radii. The hydrodynamic radii of polar kosmotropes is increased by chaotropes and decreased by polar kosmotropes. These results suggest that a chaotrope interacts with the first layer of immediately adjacent water molecules somewhat less strongly than would bulk water in its place; a polar kosmotrope, more strongly.

A molecular dynamics computer simulation study of the hydration of bis(methylsulphonyl)methane in water

The molecular dynamics computer simulation technique has been applied to study the hydration of bis(methylsulphonyl)methane (1) in water. This 1,3-disulphone has water-structure breaking properties as is deduced from both simulated time-averaged and time-dependent properties. The time-averaged properties of water molecules in the various atomic hydration shells can be directly related to the solute atom under consideration. Time-dependent properties show a mutual influencing of the hydration shells of neighbouring atoms. Moderate sulphonyl oxygen-water hydrogen bonding competes with water-water hydrogen bonding in the same hydration shell, while methylene hydrogen-water hydrogen bonding is stronger than water-water hydrogen bonding. These results are in accord with previous interpretations of 1H-N.M.R. chemical shift data for the central methylene moiety of (1) in mixtures of water with 1,4-dioxane, 1,3-dioxane, and 1,2-dimethoxyethane.

The Hofmeister effect and the behaviour of water at interfaces.

Starting from known properties of non-specific salt effects on the surface tension at an air-water interface, we propose the first general, detailed qualitative molecular mechanism for the origins of ion-specific (Hofmeister) effects on the surface potential difference at an air-water interface; this mechanism suggests a simple model for the behaviour of water at all interfaces (including water-solute interfaces), regardless of whether the non-aqueous component is neutral or charged, polar or non-polar. Specifically, water near an isolated interface is conceptually divided into three layers, each layer being I water-molecule thick. We propose that the solute determines the behaviour of the adjacent first interfacial water layer (I1); that the bulk solution determines the behaviour of the third interfacial water layer (I3), and that both I1 and I3 compete for hydrogen-bonding interactions with the intervening water layer (I2), which can be thought of as a transition layer. The model requires that a polar kosmotrope (polar water-structure maker) interact with I1 more strongly than would bulk water in its place; that a chaotrope (water-structure breaker) interact with I1 somewhat less strongly than would bulk water in its place; and that a non-polar kosmotrope (non-polar water-structure maker) interact with I1 much less strongly than would bulk water in its place. We introduce two simple new postulates to describe the behaviour of I1 water molecules in aqueous solution. The first, the 'relative competition' postulate, states that an I1 water molecule, in maximizing its free energy (--delta G), will favour those of its highly directional polar (hydrogen-bonding) interactions with its immediate neighbours for which the maximum pairwise enthalpy of interaction (--delta H) is greatest; that is, it will favour the strongest interactions. We describe such behaviour as 'compliant', since an I1 water molecule will continually adjust its position to maximize these strong interactions. Its behaviour towards its remaining immediate neighbours, with whom it interacts relatively weakly (but still favourably), we describe as 'recalcitrant', since it will be unable to adjust its position to maximize simultaneously these interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Enthalpies of solution of purine and adenine in water and in dimethylsulfoxide

Enthalpies of solution of purine and adenine in water and in demethylsulfoxide were measured calorimetrically in the temperature range 25–40°C. ΔH s o at 25°C for purine and adenine in water were found to be 18.8±0.2 and 29.9±0.7 kJ-mol−1 respectively. In dimethylsulfoxide, ΔH s o values were 13.59±0.06 and 10.84±0.05 kJ-mol−1, respectively. It is assumed that purine behaves similarly in both solvents. However, the large value for the heat capacity obtained for adenine in water is probably due to the extensive water structure breaking caused by the presence of the NH2 group on the purine ring.

Aggregation of methyl orange homologs carrying long alkyl groups in aqueous solution and their binding behaviors to poly(vinylpyrrolidone)

Methyl orange homologs having long alkyl chains, 4′-dipentylaminoazobenzene-4-sulfonate (pentyl orange) and 4′-dihexylaminoazobenzene-4-sulfonate (hexyl orange) were synthesized. Aggregation behaviors of these dyes in aqueous solutions of various additives (urea, hexamethylenetetramine, LiCl, NaCl, KCl, and CsCl) were studied by means of spectrophotometry and conductometry in connection with the role of water in aggregation process. These dyes were found to exhibit a sharp break in the plots of optical density or conductance against molar concentration of the dye, indicating that the dyes readily form aggregates at low concentrations in the aqueous solutions. The critical dye concentration for aggregate formation was obtained from the break in the plots. The effects of the additives, in particular a water-structure breaker, a water-structure maker, and counterions, on the critical concentration were investigated. Furthermore, absorption spectra of pentyl orange in the presence of varying amounts of poly(vinylpyrrolidone) were recorded. The new absorption band at shorter wavelength, which is responsible for the aggregates of the dye bound on the polymer chain, was appeared on addition of the polymer. The pentyl orange-poly(vinylpyrrolidone) complexes showed strong resemblances to the spectra of the same dye in the presence of the electrolyte and of methyl orange-polycation complexes.

Walden product, ion-solvent interactions and solvent structure in water-rich mixtures ionic conductances in water-sulfolane, water-acetonitrile and water-dimethylsulfoxide

Conductance measurements are reported for several salts in binary aqueous mixtures containing up to 60 mole % sulfolane, 20 mole % acetonitrile and 20 mole % dimethylsulfoxide. The variations of R = (λ ± 0η 0) s /(λ ± 0η 0) w with solvent composition have been compared with those observed in other water-rich mixtures. Alkali cations show R values greater than one with maxima in all the solvent mixtures. This behaviour has been discussed in terms of “sorting”, “averaging” and “steric” effects. Contrary to what happens to alkali cations, halide ions show R values greater or lesser than one according to whether the organic solvent respectively increases or decreases water structure. On these bases we suggest that conductometric behaviour of the halide ions may be indicative of the effect of the cosolvent on the water structure in water-rich mixtures and that DMSO is a water structure breaker.

Raman spectral studies of aqueous solutions of non‐electrolytes: Dimethylsulfoxide, acetone and acetonitrile

AbstractRaman spectra of aqueous solutions of dimethylsulfoxide, dimethylsulfoxide‐d6, acetone and acetonitrile are reported in the OH stretching region, and in the stretching regions of the functional groups of these solutes. Raman intensities and frequency shifts of these bands show definite trends with varying concentrations of the solutions. The results obtained are discussed in terms of the mixture model of water, and they are compared with results obtained from Raman spectral studies of aqueous electrolytes. It is proposed that water structure breaking and the formation of solute‐solvent complexes when organic solutes are added to water can account for these results.

Salt effects on the conformation of a ‘statistical’ copolymer of l-leucine and l-lysine

For studying the influence of water structure breaking and making anions on the conformation of poly(α-amino acids) containing hydrophobic and ionic side chains, c.d. measurements on ‘statistical copolymers of l-leucine and l-lysine were carried out in LiClO 4, NaClO 4, Li 2SO 4, Na 2SO 4, KF, NaF, and NaCl solutions and also in salt-free water. Copolymers with 50 mol% l-leucine do not form α-helices in pure water at pH 7 (20°C); however LiClO 4 and NaClO 4 at concentrations as low as 0.003 moll −1 induce α-helix formation almost independent of cation. Surprisingly, not only ClO − 4 but also SO 2− 4 has an α-helix inducing effect in this case, in contrast with basic homopoly (α-amino acids), where such an effect of SO 2− 4 was not observed. Therefore the presence of l-leucyl residues seems to be responsible for this α-helix inducing effect of sulphate anions. This agrees with the fact that sulphate stabilizes the ordered periodic conformation of native proteins as the increase of denaturing temperature shows. It can be assumed that the results of these measurements support the assumptions on the influence of water structure in making SO 4 anions on hydrophobic interactions, as well as of water structure breaking ClO 4 anions.

Studies of the Separation Mechanism in Ion-exchange Chromatography. III. Elution Order of cis-Bis(ethylenediamine)cobalt(III) and cis-α-Triethylenetetraminecobalt(III) Complexes on SP-Sephadex C-25 and IEX 510 Resins

Abstract Chromatographic separation of cis-dianionobis(ethylenediamine)cobalt(III) and cis-α-dianionotriethylenetetraminecobalt(III) complexes has been investigated by using SP-Sephadex C-25 and IEX 510 cation-exchange resins. The elution order of the complex cations on both resins are rather similar to each other and the adjusted retention volumes of these complexes correlate very closely with the crystallographic volumes (the unit cell volumes divided by the number of molecules in a unit cell) of [Co(X)(NH3)5]Cl2, where X=CN−, Cl−, NO2−, N3−, and NCS−. This has been taken to indicate that the affinity of the complex cation to the functional group of the resins increases as the size of the cation, and hence the character of water-structure breaker of the cation, increases. Thus, the elution order obtained seems to be determined primarily by the difference in the affinities of the complex cations to the resins, rather than by the difference in the association constants for the ion-pairs formed between the complex cation and the eluent anion.

Enthalpy titration studies of the binding of surfactants to polyvinylpyrrolidonel

The temperature dependence of the enthalpy changes that accompany the addition of several surfactants to aqueous polyvinylpyrrolidone solutions was determined by titration calorimetry. The alkyl sulfates (octyl, decyl, and dodecyl) showed signs of binding, whereas the dodecylpyridinium halides (bromide and chloride), alkyldimethylphosphine oxides (decyl and dodecyl), and dodecylsarcosinate exhibited only a general solvent effect due to the presence of the polymer (that of a water structure-breaker). The binding of dodecyl sulfate was essentially athermal (although the heat of dilution was more endothermic due to increased dimicellization), and the binding of the octyl and decyl sulfates was endothermic near 25°C. At low dodecyl sulfate binding ratios, the monomeric form of the surfactant reacted with the polymer, but 2 3 of the surfactant was bound from the micellar state as saturation was approached. The differences between the binding properties of the various surfactants cannot be explained using existing theories of hydrophobic bonding.

Adsorption of inhalation anesthetics on the air/water interface and the effect of water structure

The interaction of inhalation anesthetics with an air/water interface, and the effects of anions designated as water structure breaker (SCN −) and water structure maker (F −) upon anesthetic adsorption were studied. The values of the free energy of adsorption (-ΔG) were in the order chloroform < halothane < enflurane < diethyl ether. The values of ΔS of the adsorption of the ether-type anesthetics differ markedly from those of the alkane-type anesthetics. According to our statistical mechanical theory, it was estimated that chloroform and halothane lose one degree of freedom of the rotation by the adsorption while enflurane and diethyl ether lose two and three degrees, respectively. These losses of the rotational degrees of freedom do not mean that the rotational motion is completely frozen; rather, it transform into the vibrational mode with the resulting average frequencies in the order of the thermal vibration ( kT/h = 6 · 10 12 Hz ). The larger number of the loss of the rotational freedom with the ether-type anesthetics suggests that the hydrophilic ether oxygen may be involved. The molar affinity potentials of the anesthetics to the interface were estimated to be; chloroform, 5.4; halothane, 5.6; enflurane, 8.7; and diethyl ether, 10.7 kcal/mol. These values are inversely correlated to the anesthetic potency of these drugs with correlation coefficient of 0.999. The interaction of anesthetics with the interface was stronger on 2 M KF sub-solution than on 2 M KSCN. The ordered water structure is apparently favored for the interaction of anesthetics with water.

Properties of aqueous salt solutions of poly(ethylene oxide): Thermodynamic quantities based on viscosity and other measurements

AbstractA previous study of poly(ethylene oxide) (PEO) in aqueous salt solutions has been extended to incorporate cloud‐point measurements in potassium thiocyanate solutions (salt concentration range 3.3–3.8M where salting out occurs) and, particularly, viscosity measurements. A few osmoticpressure measurements were made and molecular weights (∼2 × 104) from gel‐permeation chromatography (GPC) compared. The theta temperature for PEO in water from cloud points was found to be 369 ± 3°K. An empirical linear relation has been found for sodium and potassium salts between the finite change of theta temperatures with change in ionic strength, δθ/δI, and (v3 − v̄3), the difference between the molar van der Waals volume and the partial molar volume of the salt. Values of the Huggins constant k′ are less than 0.5 for PEO in pure water at 303.2°K, indicating a good solvent, whereas in salt solutions they vary from 0.59 to 1.14 in nontheta solvents. They and other findings are attributed to binding of salt to the polymer and to water structure breaking. Kraemer's constants k″ were also determined: k′ − k″ = 0.5 for PEO in pure water, and for aqueous salt solutions of PEO, k′ − k″ = 0.666 at 298°K. Values of K0(= M−1/2[η]θ) with M = 2 × 104 were found to very with salt type (valence)—mean values of 103 K0/dlg−1 with number of observations in brackets are 1:1, 1.19 (2); 1:2, 1.45 (3); 2:2, 1.75 (3). Unperturbed dimensions 〈r2〉 vary from 11.0 to 12.6 nm from 1:1 to 2:2 salts. Values of the characteristic ratio Cn, the steric parameter σ, and the enthalpy and entropy of dilution parameters χH and χS have also been calculated.

Solubility of Transition Metal Complexes in Aqueous Salt Solutions. I. Tris(1,10-phenanthroline)iron(II) Perchlorate

Abstract Solubility of tris(1,10-phenanthroline)iron(II) perchlorate was determined at 25°C by spectrophotometry in aqueous solutions of sodium halides, sulfate, acetate, and trichloroacetate up to ionic strength of 0.5. It was found that the solubility is higher in the presence of water-structure breaking anions but is lower in the presence of water-structure making anions than is expected from the change in activity coefficients with ionic strength. This was interpreted in terms of compatibility and incompatibility of the influence of the complex cation on the water structure with that of added anions, and the hydrophobic nature of the complex cation was noted.