Water-organic Solvent Mixtures Research Articles

Micellization in Water-Polar Organic Solvent Binary Mixtures

Micellization of several monomeric surfactants in water-polar organic solvent mixtures has been investigated by different authors. The gradual replacement of water with other polar solvents allows one to explore the effects of solvent addition on the self-aggregation process in a wide bulk phase composition. For those polar organic solvents which are localized mainly in the bulk phase of the micellar solutions (they do not incorporate into the micellar aggregates), the variations in the cohesive energy density of the binary mixture, upon increasing the organic solvent content, seems to play a key role in the observed Gibbs energy of micellization, ΔG°M, changes. The cohesive energy density can be measured through the Gordon parameter. For a given surfactant, ΔG°M values obtained in several binary water-organic solvent mixtures can be fitted together. This ΔG°M vs. cohesive energy density correlation will permit the prediction of the variations in the Gibbs energy of micellization of monomeric surfactants upon addition of known quantities of a given polar organic solvent.

Micellization in Water-Polar Organic Solvent Binary Mixtures

Micellization of several monomeric surfactants in water-polar organic solvent mixtures has been investigated by different authors. The gradual replacement of water with other polar solvents allows one to explore the effects of solvent addition on the self-aggregation process in a wide bulk phase composition. For those polar organic solvents which are localized mainly in the bulk phase of the micellar solutions (they do not incorporate into the micellar aggregates), the variations in the cohesive energy density of the binary mixture, upon increasing the organic solvent content, seems to play a key role in the observed Gibbs energy of micellization, ΔG°M, changes. The cohesive energy density can be measured through the Gordon parameter. For a given surfactant, ΔG°M values obtained in several binary water-organic solvent mixtures can be fitted together. This ΔG°M vs. cohesive energy density correlation will permit the prediction of the variations in the Gibbs energy of micellization of monomeric surfactants upon addition of known quantities of a given polar organic solvent. Keywords: Aqueous binary mixtures, Gordon parameter, micellization, permittivity, polar organic solvents, polarity, surfactants, hydrocarbon, zwitterionic, water-organic solvent interactions

Thermochemistry of electrolyte solutions

The results of calorimetric investigations of electrolyte solutions in the mixtures of water, methanol, N,N-dimethylformamide, and acetonitrile with numerous organic cosolvents are discussed with regard to the intermolecular interactions that occur in the solution. Particular attention is given to answer the questions how and to what extent the properties of the systems examined are modified by the cosolvent added and how much the properties of the cosolvent are revealed in the mixtures with the solvents mentioned above. To this goal, the analysis of the electrolyte dissolution enthalpies, single ionic transfer enthalpies, and enthalpic pair interaction coefficients as well as the preferential solvation (PS) model are applied. The analysis performed shows that in the case of the dissolution enthalpies of simple inorganic electrolytes in water–organic solvent mixtures, the shape of the dependence of the standard dissolution enthalpy on the mixed solvent composition reflects to a large extent the hydrophobic properties of the organic cosolvent. In the mixtures of methanol with organic cosolvents, the ions are preferentially solvated either by methanol molecules or by molecules of the cosolvent, depending on the properties of the mixed solvent components. The behavior of inorganic salts in the mixtures containing N,N-dimethylformamide is mostly influenced by the DMF which is a relatively strongly ion solvating solvent, whereas in acetonitrile mixtures, the thermochemical behavior of electrolyte solutions is influenced to a large extent by the properties of the cosolvent particularly due to the PS of cation by the cosolvent molecules.

Morphology regulation and carbon coating of LiMnPO 4 cathode material for enhanced electrochemical performance

Olivine-structured LiMnPO 4 with uniform cluster-like and rod-like morphologies have been synthesized via a simple solvothermal process in water–organic solvent mixtures. The cluster-like LiMnPO 4 microstructures are composed of numerous nanoplates in thickness of ca. 35 nm and width of ca. 400 nm. Carbon is coated on the LiMnPO 4 surfaces by chemical vapor deposition (CVD) from methylbenzene and ball milling with acetylene black, respectively. The hierarchical LiMnPO 4 nanoplates deliver much higher discharge capacity and rate capability than the nanorods due to the larger interfacial area for electrochemical reaction and shorter lithium ion diffusion depth. Furthermore, carbon-coating via CVD approach leads to a significant improvement in the electrochemical performances compared to the ball milling process.

Optimization of the Selective Monohydrolysis of Diethyl 4-Aryl-4H-pyran-3,5-dicarboxylates

A simple, efficient and eco-friendly procedure for the selective monohydrolysis of diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylates under quaternary ammonium salt catalysis conditions is presented. The catalytic activities of various quaternary ammonium salts were investigated using different molar ratios of NaOH and water-organic solvent mixtures. The results indicate that the combination of 1.0 equivalent of tetraethyl-ammonium bromide (TEAB) with 1.2 equivalents of NaOH in a 10% water-ethanol media at 40 °C displays remarkable selectivity for the monohydrolysis of diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylates. The utility of this process is demonstrated by the monohydrolysis of a series of 4-aryl-4H-pyran-3,5-dicarboxylate esters to afford the corresponding monoesters in 20–80% yields under the optimized conditions.

Self-organized nano-lens arrays by intensified dewetting of electron beam modified polymer thin-films

Sub-100 nm polymeric spherical plano-convex nano-lens arrays are fabricated using short electron beam exposures to selectively modify the ultrathin (< 30 nm) polymer films, followed by their intensified self-organized dewetting under an aqueous-organic mixture. A short exposure to e-beam locally modifies the polymer chains to effectively change the viscosity of the film in small domains, thus bringing in the dynamical dewetting contrast in the film that produces aligned and ordered dewetted nanostructures. Both negative and positive e-beam tone polymers are thus used to produce array of nano-lenses. The intensified self-organized dewetting under a water-organic solvent mixture overcomes the limitations on surface tension and dewetting force and thus facilitates the formation of sub-100 nm diameter polymer nanolenses of tunable curvature. By varying the extent of e-beam exposure, various configurations from isolated to connected nano-lens arrays can be fabricated.

Sensing characteristics of the organic vapors according to the reflectance spectrum in the porous silicon multilayer structure

We fabricated a porous silicon multilayer and investigated its reflectance spectra before, during, and after exposure to various organic vapors. During exposure of the porous silicon multilayer to isopropanol, ethanol, methanol, and acetone vapors, the reflectance peak shifted toward longer wavelengths by about 5, 12, 26, and 39 nm, respectively. The shift of the reflectance peak arises from refractive index changes induced by capillary condensation of the organic vapor in the pores of the porous silicon multilayer. In addition, we observed that the shift value of the reflectance peak increased with increasing organic solvent concentration in the organic solvent-water mixture. After removing the organic vapor, the reflectance spectrum returned completely to its original state.

Organosolv extraction of lignin from hydrolyzed almond shells and application of the δ-value theory

The solubility of lignin from hydrolyzed almond ( Prunus amygdalus) shells in different acetone, ethanol and dioxane–water mixtures and conditions (extraction time and temperature) was studied. The concept of the solubility parameter ( δ-value) was applied to explain the effect of organic solvent concentration on lignin solubility. The organic solvent–water mixture that led to the highest lignin extraction was composed of a 75% vol. of organic solvent for all the solvent series investigated (acetone, ethanol and dioxane). Moreover, the best lignin extraction conditions were a temperature of 210 °C and an extraction time of 40 min for the acetone and ethanol series, and 25 min for the dioxane series. The δ-value of the hydrolyzed almond shell lignin [14.60 (cal/cm 3) 1/2] and that of the organic solvent–water mixtures was calculated. The experimental delignification capacity of the aqueous organic solvents clearly reflected the proximity of their δ-value to that of lignin. The hydrogen-bonding capacity of the solvent–water mixtures was also taken into account.

Equilibrium Swelling Studies of Chemically Cross-Linked Highly Swollen Acrylamide-Sodium Acrylate Hydrogels in Various Water-Solvent Mixtures

Swelling behavior of acrylamide (AAm)/sodium acrylate (SA) hydrogels was investigated in water-solvent (methanol, ethanol, t-butanol and acetone) mixtures of various compositions. AAm/SA hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with SA as comonomers and a multifunctional cross-linker such as trimethylolpropane triacrylate (TMPTA). Swelling experiments were performed in water and water-organic solvent mixtures of various compositions at 25°C, gravimetrically. The value of Seq% of AAm/SA hydrogels are 64–152% for 60% of metanol, 84–102% for 60% of ethanol, 127–176% for 60% of t-butanol, 131–585% for 60% of acetone, while the value of Seq% of AAm/SA hydrogels are 780–4510% for water and water-solvent mixtures. Some swelling kinetic parameters were found. Diffusion behavior of water and water-solvent mixtures was investigated. Diffusion of water and water-solvent mixtures into the hydrogels was found to be non-Fickian in character.

Erratum to: Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XI. Effects of the Preferential Solvation of Benzo-15-Crown-5 and Acid-Base Properties of the Mixtures on the Thermodynamic Functions for Complex Formation of Benzo-15-Crown-5 with Na+ in Propan-1-ol–Water Mixtures at 298.15 K

The thermodynamic functions of complex formation of benzo-15-crown-5 ether (B15C5) and sodium cation (Na+) in the mixtures of propan-1-ol (PrOH) with water at 298.15 K have been calculated from experimental measurements. The equilibrium constants of B15C5/Na+ complex formation have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by a calorimetric method. The complexes are enthalpy stabilized but entropy destabilized in the PrOH–H2O mixtures. The effects of preferential solvation of B15C5 by molecules of the organic solvent, solvation of the sodium cation, as well as the acid-base properties of propan-1-ol–water mixtures on the complex formation processes are discussed.

Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XII. Effect of the Acid–Base Properties of the Mixture on the Thermodynamic Functions of Complex Formation of Benzo-15-Crown-5 with Na+ in Water–Methanol Mixtures at 298.15 K

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.

Calorimetric studies on the coil-helix transition of poly(L-lysine) in water-organic solvent mixtures.

Calorimetric studies on the coil-helix transition of poly(L-lysine) in water-organic solvent mixtures.

Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XI. Effects of the Preferential Solvation of Benzo-15-Crown-5 and Acid-Base Properties of the Mixtures on the Thermodynamic Functions for Complex Formation of Benzo-15-Crown-5 with Na+ in Propan-1-ol–Water Mixtures at 298.15 K

Complex Formation of Crown Ethers and Cations in Water–Organic Solvent Mixtures: Part XI. Effects of the Preferential Solvation of Benzo-15-Crown-5 and Acid-Base Properties of the Mixtures on the Thermodynamic Functions for Complex Formation of Benzo-15-Crown-5 with Na+ in Propan-1-ol–Water Mixtures at 298.15 K

Micellization and interfacial behavior of imidazolium-based ionic liquids in organic solvent–water mixtures

The surface and micellar properties of aqueous solutions of two imidazolium-based ionic liquids (ILs), 1-hexadecyl-3-butylimidazolium bromide (HDBIm-Br) and 1,3-didodecylimidazolium bromide (DDDDIm-Br), are examined in the presence of several organic solvents by surface tensiometry. The organic solvents studied include methanol, 1-propanol, 1-butanol, 1-pentanol, and acetonitrile. Increases in the critical micelle concentration (cmc) values were obtained for both ILs when increasing the organic solvent content with a more significant increase observed for the DDDDIm-Br IL. For both ILs, decreases in the maximum surface excess concentration ( Γ max ), increases in the minimum surface area per surfactant molecule ( A min ), decreases in the adsorption efficiency ( p C 20 ), and decreases in the effectiveness of surface tension reduction ( Π cmc ) were obtained when increasing the organic solvent content. However, the studied organic solvents affect the surface tension at the cmc ( γ cmc ) differently; generating increases for DDDDIm-Br and decreases for HDBIm-Br. These changes can be linked to the different water–air interface orientation of both ILs in aqueous solutions free of organic solvents. Linear correlations between the extent of the change in these parameters when increasing the alkyl-chain of the alcohol modifier were also observed. A preliminary study of the utilization of HDBIm-Br in micellar–liquid chromatography (MLC) is also presented, demonstrating the applicability of the IL-aggregates in this analytical technique.

The enthalpies of solution of L-α-alanyl-L-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (T = 298.15 K) of L-α-alanyl-L-α-alanine in aqueous-organic solvents (acetonitrile, 1,4-dioxane, acetone, formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylsulfoxide) were measured at organic component concentrations x2 = 0–0.3 mole fractions. The standard enthalpies of solution (ΔsolHo) and transfer (ΔtrHo) of the peptide from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics is considered. The enthalpy pair interaction coefficients hxy between L-α-alanyl-L-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft four-parameter equation was used to reveal correlation between the hxy values and the properties of organic solvents.

Determination of sugar cane herbicides in soil and soil treated with sugar cane vinasse by solid-phase extraction and HPLC-UV

This work reports on the development and validation of a small-scale and efficient SPE-HPLC-UV method for the simultaneous determination of the most used herbicides (diuron, hexazinone, and tebuthiuron) applied to soil and soil treated with sugar cane vinasse (soil-vinasse) in areas where sugar cane crops are grown in the state of São Paulo, Brazil. The analytical procedure was optimized for solvent extraction and HPLC-UV conditions. Extraction and clean-up were combined in a single step employing solid-phase extraction, avoiding sophisticated techniques, organic–solvent–water mixtures and consequently a longer concentration step. Recovery studies with soil and soil-vinasse samples spiked at two herbicides levels (around 0.25 and 2.0 mg kg −1) and sample stability (sample frozen for 20 days before analysis) were applied as parameters to control the efficiency of the method. Good accuracy and precision were achieved with average recoveries ranging from 78% to 120% and relative standard deviations less than 10% throughout the whole recovery test. The method's limit of detection ranged between 0.025 and 0.050 mg kg −1 for diuron, hexazinone, and tebuthiuron in soil and soil-vinasse. The feasibility of this method was applied to determine the herbicide half-lives ( t 1/2) in soil and soil-vinasse in a laboratory study. Sugar cane vinasse added to soil increased the degradation of diuron and tebuthiuron ( p < 0.05), reducing the t 1/2 from 80 to 7 days and 128 to 73 days, respectively. This method is presented as an alternative which could be applied to assess herbicide behavior in soil in order to prevent water contamination and to contribute to establish pesticide limits in soil.

Hydrogen-Free Homogeneous Catalytic Reduction of Olefins in Aqueous Solutions

Herein we report a study involving the homogeneous catalytic reduction of unsaturated substrates in aqueous solutions or water-organic solvent mixtures. The reduction of olefins has been carried out in the presence of catalytic amounts of [Fe(CN)5NH3](3-) and excess of NH2OH, which under mild reaction conditions can be used to reduce carbon-carbon unsaturations without affecting carbonyl functionalities and aromatic rings. To explore the scope of the catalytic reduction, a wide variety of representative unsaturated substrates have been examined. The steric effects of the substituents on the carbon-carbon multiple bond as well as the regioselectivity and stereoselectivity of the catalyst have been studied. The deuterium kinetic isotope effect on the catalytic reduction of double bonds in olefins has been analyzed, and no significant kinetic isotope effect was found. Among the great advantages of this novel procedure for catalytic reduction are that hydrogen and high pressures are not needed, the catalyst is inexpensive and easily prepared, and water as well as water-organic solvent mixtures can be used as reaction media.

Complex formation of crown ethers with cations in water–organic solvent mixtures: Part X. Thermodynamics of interactions between Na + ion and 15-crown-5 ether in acetone–water mixtures at 298.15 K

The thermodynamic functions of complex formation of 15-crown-5 ether (15C5) with sodium cation (Na +) in the mixtures of water with acetone at 298.15 K have been calculated. The equilibrium constants of complex formation of 15C5 with Na + have been determined by conductivity measurements. The enthalpic effect of complex formation has been measured by the calorimetric method. The complexes are enthalpy-stabilized but entropy-destabilized in acetone–water mixtures. The effects of hydrophobic hydration, preferential solvation of 15C5 by a molecule of organic solvent and solvation of Na + on the complex formation processes have been discussed.

Multicomponent heterocyclization of carboxamides with H2S and CH2O

Multicomponent heterocyclization of aliphatic amides with H2S and CH2O (1:3:2) in water-organic solvent mixture in the presence of BuONa led to the formation of 1,3,5-dithiazinane in high yield (30–95%) and with high selectivity (100%). Under these conditions benzamide gave 3,5-dibenzoyl-1,3,5-thiadiazinane in 74% yield, whereas due to ortho-effect the acetylsalicylamide with H2S and CH2O in a system BuOH-H2O without BuONa formed N-acetylsalicyloyl-1,3,5-dithiazinane (80%). Heterocyclization of α-aminosuccinic acid monoamide depending on the H2S and CH2O concentration occurred either at one or both NH2 yielding respectively mono-or bisdithiazinanes.

The thermochemical characteristics of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent (acetonitrile, 1,4-dioxane, acetone, N,N-dimethylformamide, and N,N-dimethylsulfoxide) mixtures were measured at organic component concentrations x 2 = 0–0.4 mole fractions and T = 298.15 K. The standard enthalpies of solution (Δsol H°) and transfer (Δtr H°) of the peptides from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on the thermochemical characteristics of the peptides was considered. The enthalpy coefficients of pair interactions (h xy ) of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine with organic solvent molecules were calculated. The h xy values were correlated with the properties of organic solvents using the Kamlet-Taft equation.