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A simple dual impedance tester has been designed for determining the water content in organic solvents. The detection cells are formed by a pair of semi-cylindrical electrodes of aluminium foil, located opposite one another around the outer surface of a glass tube with the tested solution. Thus, the electrodes are not in contact with the analysed solution. The detection cells are connected as a capacity determining the frequency of the integrated multivibrator. The analytical signal is the difference between the frequency of the multivibrator with the measuring cell filled with the analysed solution and the multivibrator with the cell filled with pure anhydrous solvent. Solvents with various permittivities and water contents to 50% v/v were tested, with a detection limit from 0.2% (dioxane) to 1.4% (acetonitrile). The method can also be used for determining the relative permittivity of solvents with various water contents. The detector can even be used outside the laboratory because it can be powered by a standard 9-V battery. [ABSTRACT FROM AUTHOR]

Abstract: Tri-n-butyl phosphate (TBP) is a common solvent used for extracting metal ions from acidic solutions. In this work, the extraction of water and acid by TBP was modelled up to 16molal HCl, which is considerably above the range of existing work. The solubility parameter and thermodynamic equilibrium constant for the formation of each extracted species were determined using both experimental and literature data. The resulting model was able to successfully predict both the water and hydrochloric acid extraction by undiluted TBP or TBP diluted in aliphatic solvent within this concentration range. Water was shown to be extracted as the mono-hydrate at lower water activities and the di-hydrate as activity further increased. HCl was extracted as the tri-solvate at low acid concentrations, with the di-solvate , and mono-solvate forming as acid concentration increased. The present results show that at high acid concentrations, water is rejected from the organic phase as the acid is extracted, with the species formed having a typical composition of . The speciation also depends upon the extent of the dilution of TBP within the organic phase. Thus, tri-solvates are not present in undiluted TBP below 2mol/L HCl, but are present in TBP diluted in aliphatic solvent. [Copyright &y& Elsevier]

Abstract: The electric conductance of solutions of sulfuric, oxalic, benzoic, and salicylic acid (up to 0.02M) in dioxane–water mixed solvents (90% and 93% dioxane by mass) has been studied in the presence and absence of TiO2 and Al2O3 (0.5–5% by mass). TiO2 and Al2O3 enhanced the conductance of solutions of organic acids in aqueous dioxane. The conductance is interpreted in terms of adsorption of acid in molecular form, dissolution of ceramic oxides in form of anionic complexes, and leaching of acidic impurities from ceramic oxides. [Copyright &y& Elsevier]

The enthalpies of solution of ethylacetate (EtOAc) in water, octane and 1-octanol (OctOH) were measured at 298, 308 and 318 K using a precise isoperibol calorimeter. The standard enthalpies and heat capacities of these non-electrolyte solution were computed and compared with the previously obtained Δ H and $\Delta C_{p}^{\circ}$ values in N,N-dimethylformamide (DMF). Partial molal heat capacities of EtOAc in water and in organic solvents were calculated and compared with the available literature values. [ABSTRACT FROM AUTHOR]

Abstract: To develop an efficient green extraction approach for recovery of bioactive compounds from natural plants, we examined the potential of pressurized liquid extraction (PLE) of ginger (Zingiber officinale Roscoe) with bioethanol/water as solvents. The advantages of PLE over other extraction approaches, in addition to reduced time/solvent cost, the extract of PLE showed a distinct constituent profile from that of Soxhlet extraction, with significantly improved recovery of diarylheptanoids, etc. Among the pure solvents tested for PLE, bioethanol yield the highest efficiency for recovering most constituents of gingerol-related compounds; while for a broad concentration spectrum of ethanol aqueous solutions, 70% ethanol gave the best performance in terms of yield of total extract, complete constituent profile and recovery of most gingerol-related components. PLE with 70% bioethanol operated at 1500psi and 100°C for 20min (static extraction time: 5min) is recommended as optimized extraction conditions, achieving 106.8%, 109.3% and 108.0% yield of [6]-, [8]- and [10]-gingerol relative to the yield of corresponding constituent obtained by 8h Soxhlet extraction (absolute ethanol as extraction solvent). [Copyright &y& Elsevier]

The self-assembly of structurally discrete entities, and supramolecular chemistry in general, continues to expand into the aqueous realm. To do so, however, requires a firm understanding of the properties of aqueous solution, and how these 'change the rules' for binding and assembly relative to organic solvents. In this mini-review we highlight the state-of-the-art understanding of the supramolecular properties of water, and how these influence the design of hosts and self-assembling systems. [ABSTRACT FROM AUTHOR]

A simple and reliable method for preparing tips coated with poly(dimethylsiloxane) (PDMS) for scanning tunneling microscopy (STM) in aqueous solutions is reported. Au STM tips were dip-coated with PDMS and subsequently cured. The coated tips were characterized by scanning electron microscopy, energy dispersive x-ray spectroscopy, and voltammetry. We show that the PDMS layer smoothly covers the tip surface except for its very apex. These tips enable atomically resolved imaging of a sample surface and measurement of single-molecule conductance below 1.0 nS with STM in aqueous solutions. Because of the superior compatibility of PDMS with organic solvents, the PDMS-coated tips would be useful for preparing molecular tips via their chemical modification in such solvents, enabling chemically selective imaging of a single molecule in water. [ABSTRACT FROM AUTHOR]

The metastable zone widths (MZWs) of triethanolamine hydrochloride ([HTEA]Cl), defined as the maximum temperature difference ΔTmaxa solution can withstand before crystallization of a solid phase, in water, ethanol−water, and HCl−water mixed solvents have been determined at a saturation temperature T0range from 293.15 to 303.15 K with cooling rate Rfrom 3 to 8 K·h−1. Solubilities of [HTEA]Cl in ethanol−water mixtures have also been obtained using a dynamic method. An equation of MZW with similar form to Sangwal’s equation was derived from the fundamental driving force of crystallization based on chemical potential. With the newly obtained equation, the experimental values of MZW ΔTmaxfor [HTEA]Cl−water system at 298.15 K was correlated with the cooling rate Rby ln(ΔTmax/T0) = −6.140 + 1.222 ln R. The enthalpy of mixing ΔHmixwas calculated with the solubility data, and the result of differential scanning calorimetry (DSC). For [HTEA]Cl−water system, the value of −ΔHmixwas determined to be 30.88 kJ·mol−1, and the addition of both HCl and ethanol led to a decrease of −ΔHmix. The experimental results also showed that MZW could be greatly enhanced when ethanol and HCl were added. It was found that the values of MZW decrease with −ΔHmixfor both [HTEA]Cl−ethanol−water and [HTEA]Cl−HCl−water systems at the same saturation temperature and cooling rate. [ABSTRACT FROM AUTHOR]

Water soluble poly (vinyl alcohol) (PVA) was used to prepare the enzyme membranes of acetylcholinesterase (AChE) for electrochemical assaying methyl parathion in water insoluble organic solvent. The immobilized enzyme was separated from electrode for the development of enzyme inhibition-based bioassays. This assay is simple and convenient where enzyme membrane is applicable for single use and the electrode for repeated use. The enzyme membranes can be used handily piece by piece and the released AChE performs catalytic reaction homogeneously. The inhibition percentage of AChE increases with the concentration of methyl parathion ranging from 0.1 to 1 mg/mL. [ABSTRACT FROM AUTHOR]

Effects of three organic solvents, viz. methyl cellosolve, acetonitrile, and formamide, on the micellization process of Gemini surfactant pentamethylene-1,5-bis(tetradecyldimethylammonium bromide) aqueous solutions, with the volume percentages of the organic solvents up to 50%, have been investigated conductometrically. The studies were made at different temperatures and the data were used to find out different micellization parameters. From the study, it was observed that, although an increment in the amount of the organic solvents delays the micellization, the increase in the critical micelle concentration (cmc) is comparatively less below 20%(v/v) showing the predominance of water character in the bulk phase at lower compositions of the organic solvents. Applying equilibrium model for micelle formation, various thermodynamic parameters were also calculated from the temperature dependence of the cmc values and the results show that the micellization process becomes less spontaneous as the volume % of the organic solvent increases in the system due to the action of water-organic solvent mixed media as better solvent than pure water (solvophobic effect) for the studied Gemini molecules. [ABSTRACT FROM AUTHOR]

The modelling of the habit modifying effect of water on crystalline substances is still problematic, since the approaches for morphology prediction are investigated for organic molecules rather than for inorganic molecules. Therefore, selected well known 3-, 4- and 5-site water models have been implemented as the solvent in a molecular modelling method. By means of the surface docking method, the investigations on crystalline benzoic acid aimed to model the effect of water as a solvent. The modelling comprised additional geometry constraints of water as a flexible and a rigid molecule. By proof of experimental results, one 3-site water model was favoured for the application in morphology predictions. Future modelling work will be simplified, since it can focus on one single model of water. Furthermore, corresponding to the desired level of supersaturation, the best model can be taken from a modelling toolbox. [ABSTRACT FROM AUTHOR]

[60]Fullerene has zero solubility in water and very low solubility in many organic solvents. It was found that it forms reverse micelles in organic solvents in the presence of nonionic surfactants. Reverse micellization studies of fullerene solutions in the presence of a nonionic surfactant (Span60) were carried out, and the thermodynamic quantities of the reverse micellization process derived from experimental results indicate that the process is spontaneous. The solution behavior of the [60]fullerene was understood from its ability to form microemulsions from its toluene solution and water using different nonionic surfactants. Light scattering studies showed that the dimensions of these microemulsions reach a maximum of 170 nm. Phase behavior at different temperatures indicates the very high surface active nature of [60]fullerene. [ABSTRACT FROM AUTHOR]

Using a laser monitoring technique, the solubility data of taurine in water and aqueous solutions of methanol, ethanol, and 2-propanol were measured over the temperature range from (274.05 to 353.05) K. From the experimental data, the solubility data of taurine in the mixtures of water methanol, water ethanol, and water 2-propanol were found to increase with increasing temperature and decrease with increasing concentration of methanol, ethanol, and 2-propanol in aqueous solution. Also, the water ethanol solution was a better solvent for the purification of taurine. The Apelblat equation, the simplified model of ideal solution, and the λhequation were used to correlate the solubility data; the results showed that the three models mentioned above agreed well with the experimental data, and the Apelblat equation was the most accurate of all of these for these systems. [ABSTRACT FROM AUTHOR]

Abstract  The enthalpies of solution of benzo-15-crown-5 ether in methanol–water mixtures and methanol–water–sodium iodide systems have been measured at 298.15 K. The values of standard enthalpies of solution of benzo-15-crown-5 ether are positive in the mixtures of water and methanol within the whole range of mixture composition. The equilibrium constants of complex formation of benzo-15-crown-5 ether with the sodium cation have been determined by conductivity measurements at 298.15 K. The thermodynamic functions of the formation of these complexes have been calculated. The Gibbs energy of complex formation depends on the base–acid properties of methanol–water mixture. [ABSTRACT FROM AUTHOR]

Abstract: Clegg–Pitzer–Brimblecombe ion-interaction semi-empirical approach was rarely exploited for modeling electrolyte, particularly, in mixed solvent systems. Indeed, a review of the literature shows that the use of an exact and complete form of this model (PSC) was only limited to the works of two research groups for the investigation of electrolyte in mixed solvent systems. In this work, we have used both Pitzer and PSC ion-interaction theoretical approaches for modeling the non-ideal behavior of HCl in the ternary HCl+methanol+water electrolyte system. The modeling purposes were achieved based on the experimental determination of the mean molal activity coefficients for HCl in this ternary system by using the potentiometric data of a galvanic cell containing a pH glass membrane and Ag/AgCl electrodes. The measurements were performed over the electrolyte molality ranging from 0.01 up to 5.75mol/kg in mixed methanol (x%)+water (100− x%) solvent, with solvent mass fraction percents: x%=10, 20, 30, 40 and 50%, at 298.15±0.05K. [Copyright &y& Elsevier]

Abstract: A LFE (Linear Free Energy) analysis of kinetic data for different organic reactions in various organic aqueous solutions was carried out. The rate constants of these reactions were compared with those for the solvolysis of tert-butyl chloride in the same solvents in terms of the LFE Relationships, and linear plots were observed in a wide range of the co-solvent content. This similarity points to a common nature of the solvent effect in these reactions in variety of water–organic mixtures, regardless of largely different reaction mechanisms. We explain these results by the prevalence of hydrophobic stabilization of the initial state of these reactions in water-rich solvent mixtures. Recently the same conclusion was also made on the basis of investigations into sonication effects in kinetics of organic reactions. A considerable contribution of hydrophobic effects to the Y scale by Grunwald and Winstein was deduced. [Copyright &y& Elsevier]

Abstract: Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline–aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and 13C NMR spectroscopy, as well as by SEM techniques. [Copyright &y& Elsevier]

Abstract: An efficient method for the conjugate addition of unactivated alkyl iodides to α,β-unsaturated carbonyl compounds using indium/copper in water is described. The reactions proceed more efficiently in water than in organic solvents. In, CuI, and InCl3 are all essential for efficient reaction. Formation of a symmetrical vic-diarylalkane is observed when an aryl-substituted alkene is used as substrate. [Copyright &y& Elsevier]

Abstract: The asymmetric transfer hydrogenation of nonfunctionalized aromatic ketones catalyzed by Ru-TsDPEN was performed successfully in a mixture of poly(ethylene glycol) (PEG) and water. High activity and enantioselectivity were obtained, which were better than or comparable to those obtained in conventional organic solvents. The unmodified catalyst could be easily recovered after extraction of the reduced product with a less polar solvent such as hexane, and was reused at least 14 times without obvious loss in enantioselectivity. These results indicate that the inexpensive and non-toxic aqueous PEG can serve as a new means for the immobilization of Ru-TsDPEN catalyst and related variants without calling for catalyst modification. [Copyright &y& Elsevier]

Abstract: In this work, densities of binary mixtures of {water+formamide (FM), or + N,N-dimethylformamide (DMF), or +dimethylsulfoxide (DMSO), or + N,N-dimethylacetamide (DMA), or +1,4-dioxane}, have been determined under atmospheric pressure as a function of composition and temperature using a vibrating-tube densimeter. The temperatures studied were T =(288.15, 293.15, 298.15, and 303.15) K. The excess molar volumes , calculated from density data, are negative over the whole mole fraction range for the temperature range studied. The values have been fitted to Redlich–Kister polynomial equation and others volumetric properties were calculated. The partial molar volumes at infinite dilution of each component have been determined using three different methods. [Copyright &y& Elsevier]

The nature of the rate enhancements caused by gradually increasing the mole traction of water in the solvent (from 0 to 1) for the cycloaddition reactions of pyridazinium-dicyanomethanide 1,3-dipole, 2, with the dipolarophiles ethyl vinyl ketone (a water-super dipolarophile) and methyl acrylate (a water-normal dipolarophile) in the organic solvents acetonitrile, acetone, methanol, ethanol, and tert-butyl alcohol at 37 °C are explored. In each case as the mole fraction of water surpassed ca. 0.9, exponential rate enhancements were triggered. When methanol replaced water, the rate enhancements were smaller, and no triggering effect was observed. The dramatic rate enhancement triggered for the water-super dipolarophile was significantly reduced as the temperature was raised in the range 29-64 °C. The results suggest that a dominant hydrogen-bonding effect operates in water-induced rate enhancements of 1 ,3-dipolar cycloaddition reactions with water-super dipolarophiles as well as the hydrophobic effect. The hydrogen- bonding effect involves secondary bridging hydrogen bonding from the primary water-solvation shell of the transition state and the growth of structured water clusters. Theoretical calculations strongly support these conclusions. [ABSTRACT FROM AUTHOR]

The article focuses on the significance of mechanistic differences between the transfers of hydrophilic and hydrophobic ions to low-polarity solvents. It differentiates hydrophobic ions and hydrophilic ions capability of transferring water to organic solvents. Furthermore, it emphasizes the significance of the amount of hydrophilic ions in its ability to increase water concentration in organic phase.