Organic Solutes In Water Research Articles

The new role of dipyrromethene chemosensor for absorbance-ratiometic and fluorescence “turn-on” sensing Zn2+ ions in water-organic solutions and real water samples

This study presents a dipyrromethene-based sensitive and selective probe for Zn2+ ions detection in aqueous and water-organic media. The probe demonstrates absorbance-ratiometric and “off-on” fluorescent sensing for Zn2+ in a DMSO/H2O (9:1, v/v) mixture. The 3,3′,4,4′,5,5′-hexamethyl-2,2′-dipyrromethene (HL), similar to its analogs, exhibits weak fluorescence (with a quantum yield of less than 0.001). However, upon the presence of Zn2+ ions in the sensor HL solution, there is a remarkable increase (up to 200-fold) in fluorescence intensity due to the formation of a stable intramolecular chelate complex [ZnL2]. This complex formation induces a significant hyperchromic effect and a red shift (57 nm) in the characteristic absorption bands. The sensing mechanism of the probe towards Zn2+ ions was thoroughly investigated through absorbance and fluorescent titrations, molar ratio plots, 1H NMR, and DFT/TDDFT studies. The fluorescence response exhibited a strong linear relationship with Zn2+ concentration within the range of 0 to 5.7 × 10–6 mol/L. The detection limit (LOD) and limit of quantitation (LoQ) for Zn2+ were determined as 2 × 10–8 mol/L and 6.6 × 10–8 mol/L, respectively. Moreover, the probe demonstrated high selectivity for Zn2+ ions over other metal ions (Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Pd2+, Cd2+, Hg2+, Pb2+). Test systems in the form of test-strips and cotton-pads were developed based on the dipyrromethene sensor for rapid “naked-eye” detection of zinc ions in water. The sensor was successfully applied for detecting Zn2+ ions in real water samples.

Correlating Pure Component Properties with MOSCED Solubility Parameters: Enthalpy of Vaporization and Vapor Pressure

Tools to predict vapor–liquid phase equilibria are indispensable for the conceptualization and design of separation processes. Modified separation of cohesive energy density (MOSCED) is a solubility-parameter-based method parameterized to make accurate predictions of the limiting activity coefficient. As a solubility-parameter-based method, MOSCED can not only make quantitative predictions, but can shed light on the underlying intermolecular interactions. In the present study, we demonstrated the ability of MOSCED to correlate the enthalpy of vaporization and vapor pressure at a specific temperature using multiple linear regression. With this addition, MOSCED is able to predict vapor–liquid phase equilibria in the absence of reference data. This was demonstrated for the prediction of the Henry’s constant and solvation free energy of organic solutes in water, which was found to be superior to mod-UNIFAC. In addition to being able to make phase equilibrium predictions, the ability to correlate the enthalpy of vaporization and vapor pressure offers the opportunity to include additional properties in the regression of the MOSCED parameters. Given this success, we additionally attempted to correlate a wide range of physical properties using a similar expression. While, in some cases, the results were reasonable, they were inferior to the correlations of the enthalpy of vaporization and vapor pressure. Future efforts will be needed to improve the correlations.

Spectroscopic and Kinetic Investigations of the Permeability of the Surface Layers of Membranes in the Process of Microfiltration Separation of Water-Organic Solutions

Spectroscopic and Kinetic Investigations of the Permeability of the Surface Layers of Membranes in the Process of Microfiltration Separation of Water-Organic Solutions

Study of radical polymerization of diallyl monomer based on allyl bromide and piperidine

In this article, kinetic feature of N, N-diallylpiperidine bromide radical polymerization is investigated. Orders of reaction are determined by the monomer and by the initiator. Essential value in this regard acquire investigation of implementation mechanism on elementary acts of radical polymerization N-alkyl - N, N-diallylamines and their proton salts at initial extents of transformation in water and water-organic solutions. Specific cyclolinear polymerization of diallyl monomers salt allows excluding the act degraded transfer of the chain on monomer and gives the chance of receiving polymers with high molecular weight. Data of kinetic researches testify the lack of degradation inherent chain transfer. It is noted that polymerization rate decreases while adding monomer ethanol to water solution. NMR 13C-spectroscopic researches of the polymers received by radical polymerization of N, N-diallylpiperidine bromide testifies the existence in chains of macromolecules as to five - (48%), and six-membered cycles (52%) which are calculated from a ratio of intensity of signals of the corresponding carbon atoms. The combination of polymeric, surface active and electrolytic properties of the synthesized polymer leads to the new qualitative state possessing a number of specific features shown in conformational and electrochemical behavior of polymer solution. Finding these properties will cause assessment opportunities of synthesized polymer usage as cationic flocculants, coagulants, precipitators and other purposes. Therefore, as distinct from anion and nonionic flocculants, cationic flocculants show high efficiency on application of them for extraction of organic and colloidal pollution and sedimentation of the weighed particles. Besides big advantage of cationic flocculants is the absence of their corrosion action on metals.

Dispersion of the sound speed in water-organic solutions

Concentration and temperature studies of spontaneous Mandelstam-Brillouin scattering of light in aqueous solutions of γ-picoline showed the manifestation of negative dispersion of hypersound velocity at concentrations С ≤ 0.2 mole fractions of γ-picoline. The temperature and concentration dependences of the negative dispersion are associated with the process of solution structurization, which reaches its optimum value at a concentration of C = 0.06 mole fractions of γ-picoline.

Conformational Changes in the Structural Characteristics of MFFK-3 and PP-190 Polymer Films during the Purification of Water–Organic Solutions

Conformational Changes in the Structural Characteristics of MFFK-3 and PP-190 Polymer Films during the Purification of Water–Organic Solutions

Counterion effect on α-Keggin polyoxometalates in water: The peculiar role of H+ on their salting-in effect and co-assembly with organics

Hofmeister effects of ions in aqueous solution strongly affect chemical and biological systems. High and low charge density anions, such as SO42- and SCN- respectively, decrease (salting-out) or increase (salting-in) the solubility of organic solutes in water. Due to their very low charge-density, nanometric anions, e.g. polyoxometalates (POMs), increase the solubility of organic solutes tremendously (highly salting-in) as they bind to neutral hydrated solutes strongly – a property that is attributed to the (super-)chaotropic effect. Here, we show that salting-out anions can be turned into salting-in anions in the presence of a superchaotropic POM, α-PW12O403-. The effect of salts composed of salting-out anions, e.g. SO42-, was investigated on the cloud point (CP) of an ethoxylated surfactant (C8E4) and a propoxylated co-solvent (C3P2) in the presence of SiW12O404- and PW12O403- with different counter-cations (H+, Li+, Na+, K+). SiW12O404- and PW12O403- lead to a monotonic strong CP-increase regardless of the counterion, except for PW12O403- combined with H+. Indeed, H3PW12O40 shows a CP decrease at high POM concentrations. This peculiar behavior is attributed to the formation of large H3PW12O40-C3P2 (and H3PW12O40-C8E4) co-assemblies, as shown by SAXS. The formation of these co-assemblies results from the “bridging” effect of H+ and the lower charge density of PW12O403- compared to SiW12O404-. The addition of (basic) salting-out anions leads to (i) the consumption of H+, then to (ii) the disruption of the large H3PW12O40-C3P2 (and H3PW12O40-C8E4) co-assemblies and subsequently to (iii) a CP-increase. In the peculiar case, this shows how commonly used salting-out anions can become apparently salting-in.

SYNTHESIS AND STRUCTURE OF HETEROMETALLIC – MIXED-LIGAND Ge(IV) – 3d-METAL COMPLEXES WITH GALLIC ACID AND 1,10-PHENANTHROLINE

Authors have developed optimal conditions and synthetic methods in water-organic solutions for ten heterometallic – mixed-ligand complexes of germanium(IV) and 3d-metals with gallic acid (Н2Gal) and 1,10-phenanthroline (phen), their composition and structure [M(phen)3][Ge(H2O)(HGal)2]∙nH2O (M = Mn (1), Co (2), Ni (3), Zn(5)); [CuCl(phen)2]2[Ge(H2O)(HGal)2]∙2H2O (4). Comparative analysis of their IR-spectra and spectra gallic acid and 1,10-phenanthroline with involvement diffuse reflection spectra allowed to establish coordination sphere of germanium and 3-metals. IR-spectra of complexes 1-5 are similar, therefore coordination of ligands in them is the same. Comparatively to the IR-spectrum of gallic acid, there are absent valence absorption bands of free carboxylic groups while two bands of asymmetric and symmetric oscillation of C-O groups in carboxylate ions CОО- appear in the spectra of complexes. Deformation bands d(Сarom-О-Н) are shifted to the low-frequency region for 50-40 cm-1, which indicates deprotonation and binding to the complexing agent of OH-groups from gallic acid. Appearance of deformation bands d(H2О) at 1625 сm-1 is characteristic for the coordination water in composition of complexes. Presence of coordination and crystalline water as well as unbonded OH-group are confirmed with the band n(Ge-О) at 620 сm-1. Thermal decomposition of mixed-metal complexes starts with an endothermic effect in the temperature range 80-160°С where elimination of certain number of water molecules takes place: two – for 1 and 4, three – for 2 and 5, four – for 3. On the thermogravigrams of all compounds one more endoeffect in the temperature range 160-220°С is presented, where removal of one coordination water molecule happens. It was established, that coordination polyhedron of germanium was formed by five oxygen atoms of deprotonated hydroxyl groups from two molecules of gallic acid and one water molecule in all compounds. Second ligand – 1,10-phenanthroline is coordinated to 3d-metal through heterocyclic nitrogen atoms with formation of cations with different composition [M(phen)3]2+ (M = Mn, Co, Ni, Zn) та [CuCl(phen)2]+.

Glycol and Phosphate Depot Forms of 4- and/or 5-Modified Nucleosides Exhibiting Antibacterial Activity

Resistance developed to the majority of drugs used to treat infectious diseases warrants the design of new compounds effective against drug-resistant strains of pathogens. Recently, several groups of modified nucleosides have been synthesized and showed significant antibacterial activity in vitro, but their further studies were difficult to undertake because of their low solubility in aqueous solutions. Nevertheless, new compounds, well soluble in water-organic solutions, were synthesized and found to be more effective in inhibiting the growth of Gram-positive bacteria and mycobacteria. The water-soluble forms of modified nucleosides under study were assumed to be their depot forms. To check the assumption, the compounds were tested for hydrolysis in various media and their molecular docking was performed into the active center of the putative target, Mycobacterium tuberculosis flavin-dependent thymidylate synthase ThyX. Computer modelling showed that the water-soluble analogs do not act as ThyX inhibitors, supporting the assumption of their depot nature. The compounds were resistant to chemical hydrolysis but were hydrolyzed when incubated with porcine liver carboxylesterase, human serum, or Staphylococcus aureus 209P. The results demonstrate that the compounds are most likely depot forms of modified nucleosides.

Green Synthesis of 2-Phenylbenzothiazole in Aqueous Hydrotropic Medium and its Process Intensification by Ultrasound

Benzothiazole has potent and significant biological activity, which makes it an important compound in many areas. Synthesis of benzothiazole is also of interest for organic synthetic chemists. The synthesis mainly takes place by condensation of 2-aminothiophenol with a carbonyl functional group of an aldehyde or, a carboxylic acid or other derivatives followed by cyclization. Different methodologies, such as use of transition metal catalysts, different solvents, temperature variation, enzymatic catalysis, etc., have been applied for improving the synthesis of benzothiazoles. Synthesis of organic compounds in water is of interest in current research because of the benign nature of water. But poor solubility of many organic reactants in water however restricts the reaction progress. Hydrotrope as an additive, however, increases the solubility of sparingly soluble or insoluble organic solutes in water, which helps to enhance the rate of reaction and conversion of reactants and to improve the yield of the product. The use of hydrotrope and reaction set up are not tedious, while recovery of product and reuse of hydrotrope are easy. Here, we report benzothiazole synthesis in the aqueous medium of sodium cumene sulphonate as a function of hydrotrope concentration and temperature. This scheme gives an average 97% yield of benzothiazole by conventional heating. The hydrotrope recycle by three times, without any treatment, gave 95% product yield. The method is easy to handle with reduced reaction time, and generates no waste. It increases productivity as the recovery of the product happens by mere precipitation of the product. Process intensification in an indigenously developed ultrasonic batch reactor gave 98% yield of the product in 30-45 min as against 1-2h without ultrasound.

Non-Ostwald Behavior of Disperse Systems in Evaporation and Crystallization of Droplets of Water–Organic Solutions

This Letter describes experiments with aqueous solutions of organic substances demonstrating a non-Ostwald behavior under which the stability of small droplets during evaporation and crystallization is higher than that of large droplets. Such a behavior has been described earlier for aqueous solutions of some inorganic salts. It is shown that the non-Ostwald behavior has a common thermodynamic nature with Ostwald ripening and should be observed in disperse systems with a complex chemical composition. The features of reproduction of the non-Ostwald behavior related to the surface activity of organic substances in aqueous solutions are described. The studied regularities can be used upon preparation of solutions of organic and bioorganic substances with a concentration significantly higher than their solubility under normal conditions, as well as for the formation of narrow size distributions in different spray processes.

Chromatographic behavior of benzimidazole derivatives on hypercrosslinked polystyrene by reverse-phase HPLC

An important part in the research of separation of various compound classes is the study of relationship between structure and property by describing the effect of structure on compounds’ chromatographic retention. The aim of this work was to study the chromatographic retention of the firstly synthesized benzimidazoles from water-acetonitrile and water-methanol solutions on hypercrosslinked polystyrene (HCP) by high-performance liquid chromatography (HPLC). The effect of water-methanol and water-acetonitrile solutions’ composition on the benzimidazole derivative retention factors on HCP was studied. The thermodynamic characteristics of sorption of benzimidazoles’ transition from water-organic solutions onto the surface of HCP phase were obtained. The thermodynamic compensation effects were studied. It has been shown that the benzimidazole nitro derivative realizes additional specific interactions with the aromatic network of HCP. The slope ratio of the Soczewiński–Wachtmeister equation was calculated. It was shown that 1-hydroxymethylbenzimidazole and 2-aminobenzimidazole characterized by small volumes and containing hydrophilic substituents do not subordinate Soczewiński–Wachtmeister model under ranging from 75 to 85% concentrations of acetonitrile.

Влияние химического строения и линейной плотности заряда сульфонатсодержащих ароматических полиамидов на взаимодействие с поликатионами в органической и водно-органической средах

The interaction of sulfonate-containing aromatic poly- and copolyamides with acrylonitrile copolymers with N,N-dimethyl-N,N-diallylammonium chloride (DMDAAC) and N,N-diethylaminoethylmethacrylate (DEAEM) in organic and water-organic solutions was studied. It was shown that as a result of macromolecular reactions interpolyelectrolyte complexes (IPEC) forms. They are stabilized mainly by electrostatic forces. To characterize the interpolyelectrolyte complexes composition the φ parameter was used, that defines as the ratio of corresponding functional groups molar concentrations of interacting polyelectrolytes. The transformation degree in interpolymer reactions θ was calculated as the ratio of the salt bonds number between polyions to their maximum possible number. It was shown that the main factors determining the composition and structure of forming interpolyelectrolyte complexes are linear charge density of polyelectrolytes, the nature and composition of the solvent in which interpolymer reactions occurs. It is possible to obtain IPEC, the composition of which for the same polycation will vary from φ = 2.5 to φ = 1.0, changing these factors. It was found that at the complexation process is not accompanied by a change in the phase state of the interpolymer system, when the concentration of units with sulfonate groups in the macromolecular polyamide chain 5 mol.%. It was found that the introduction of polycation leads to the formation of IPEC structures in the form of particles with an average size of ~217.7 nm for poly-4,4'-(2-sodium sulfonate) – diphenylaminisophthalamide and ~248.1 nm in the case of poly-4,4'-(2-sodium sulfonate) -diphenylaminterephthalamide. It was shown that the decrease in the polymer content of units with sulfonate groups is accompanied by a decrease in the transformation degree from 0.65-0.66 to 0.18. It was found that the studied complexes can be transferred to the solution by increasing its ionic strength. The result obtained during this work can serve as a base for the development of for the manufacturing technology of film and membrane materials based on sulfonate-containing aromatic poly- and copolyamides.

Thermodynamics of the Adsorption of Isomeric Dipyridyls and Their Derivatives from Water–Organic Solutions on HYPERCARB™ Porous Graphitic Carbon

High-performance liquid chromatography is used under near-equilibrium conditions to study the adsorption of isomeric dipyridyls and their derivatives from water–acetonitrile, water–methanol, and water–isopropanol solutions onto Hypercarb™ graphite-like carbon material in the region of Henry’s law. Hypercarb™ graphite-like carbon material exhibits high adsorption selectivity in separating the investigated isomeric dipyridyl and its derivatives. It is shown that the possibility of forming strong intramolecular C–H–N'-hydrogen bonds in a molecule of 2,2'-dipyridyl or its derivatives strengthens the adsorption bonding of adsorbate molecules and the surface of the graphite-like material due to stabilization of their planar conformation. Destabilizing this intramolecular hydrogen bond by adding substituents in different positions of the pyridine rings enhances the specific intermolecular interaction between adsorbate molecules and the solvent’s components and distorts the planar conformation of dipyridyls, weakening their retention on the Hypercarb™ material. Positive adsorption from the water–organic medium on the carbon adsorbent is observed for all of the investigated dipyridyls, with the exception of 2,2'-dipyridyl-N,N '-dioxide, which is adsorbed weaker than the solvent components. Anomalous medium–property dependences are found for the thermodynamic characteristics of the adsorption of dipyridyls on porous graphitic carbon, and are attributed to the predominance of adsorbate–adsorbent π–π interactions over hydrophobic ones and the resolvation of adsorbate molecules with acetonitrile in proportion to lowering the content of water in the bulk solution.

Partial molar volumes of organic solutes in water. XXX. Two poly(ethylene glycol) monoalkyl ethers, C4E2 and C1E3, at temperatures T = 298 K to 573 K and pressures up to 30 MPa

Densities of dilute aqueous solutions of two aliphatic poly(ethylene glycol) monoalkyl ethers, H-(CH2)4-(O-CH2-CH2)2-OH (diethylene glycol monobutyl ether, C4E2) and H-CH2-(O-CH2-CH2)3-OH (triethylene glycol monomethyl ether, C1E3) measured in the temperature range from (298 to 573) K and at pressures up to 30 MPa using an automated flow vibrating-tube densimeter are reported. Standard molar volumes were evaluated from the measured data. A comparison with data previously measured for selected members of the homologous series of similar solutes (poly(ethylene glycols), glymes, 2-alkoxyethanols) is presented.

(Non)Existence of Bulk Nanobubbles: The Role of Ultrasonic Cavitation and Organic Solutes in Water.

A drawback of studies on bulk nanobubbles is the absence of direct proof that the nano-objects reported are really nanobubbles. The aim of our work was to provide such a proof or disproof. We focused on two effects (processes) commonly considered in research on nanobubbles: ultrasonic cavitation and addition of organic compounds to water, which could create in principle a barrier at the gas/water interface contributing to the stability of nanobubbles. We found that both of these processes lead to the generation of nano-objects, which are, however, not bulk nanobubbles. Ultrasonication leads to the formation of fine metal nanoparticles originating from the disintegration of the surface of the metal ultrasonic probe. Addition of organic solutes to water leads to the formation of a population of nanoparticles/nanodroplets originating from the so-called mesoscale solubilization of hydrophobic compounds present in the added solute as molecularly dissolved impurities. Subsequent ultrasonication of such mixtures adds metal nanoparticles and only slightly modifies the size distribution of mesoscale particles. While our results do not dismiss existence of nanobubbles in general, described effects must be seriously taken into account, especially in the case of biomedical applications where they can result in serious side effects.

Recognition and Binding of Aliphatic Dicarboxylic Acids C4 – C10 by Diiminocalix[4]arene

Host-Guest complexation of 5,17-bis-(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arenewithaliphatic dicarboxylicacidsC4 – C10 hasbeenstudiedin water-organic solution by the RP HPLC and molecular modeling methods. The stability constants (log KA =2.56– 3.05) of the supramolecular complexes are depended on structure, pKa and log Pvalues of the acids. The complexation is determined by the hydrogen bonds of the COOH group of the dicarboxylic acids with nitrogen atoms at the upper rim or oxygen atoms at the lower rim of the calixarene.

Conversion of water-organic solution of sodium naphtenates into naphtenic acids and alkali by electrodialysis with bipolar membranes

The process of recovery of sodium naphtenates into naphtenic acids and sodium alkali using electrodialysis with bipolar membranes is investigated. A membrane stack of an electrodialyzer with a three-chamber unit cell in which the salt chamber is formed by two cation-exchange membranes is proposed, which eliminates the transfer of anions from the salt chamber to an adjacent alkaline and acidic one. The values of current efficiency for naphtenic acid and alkali, as well as energy consumption for the process, are determined. It is shown that the main problems with the development of electro-membrane technology for producing naphtenic acids from petroleum and petroleum products are associated with micelle formation of a mixture of naphtenic acids with sodium naphtenate in the pH = 6.5–8 range, which leads to a sharp increase in the viscosity and electrical resistance of solutions. Introduction of the cation-exchanger and sodium sulfate to the intermembrane space of naphtenthe salt chamber can significantly improve the technical and economic characteristics of the process - for example, the specific energy consumption decrease from 0.86 kW h·L−1 down 0.38 kW h·L−1, which is more than two times lower than the original three-chamber cell. At the same time, the production of naphtenic acids remains on the same level which is 17 L·m−2·h−1.

Spectrophotometric Evaluation of L-Lysine Concentrations in Water–Organic Solutions

In this work, the conditions of spectrophotometric evaluation of the ninhydrin assay for L-lysine in a water dimethyl sulfoxide solution were investigated. The absorption spectrum of the L-lysine–ninhydrin reaction product exhibited two maxima at 420 and 500 nm. It was shown that pH of the reaction medium affected the intensity of the product color. The stability of the ninhydrin reaction products was the highest at pH 8–9. The phase proportion of the water–organic solution had little effect on the optical density of the product. The absorption spectra of the ninhydrin reaction products of L-lysine derivatives: Nα-boc-lysine and Ne-z-lysine, indicated that it was the α amino group of lysine that participated in the reaction.

Regularities of adsorption of water-soluble vitamins on the surface of microdispersed sintered detonation nanodiamond

Adsorption of water-soluble vitamins, including riboflavin (В2), nicotinamide (PP, B3), pyridoxine (B6), cyanocobalamine (В12) from water-organic solutions on microdispersed sintered detonation nanodiamond (MSDN), modified in different ways, was studied using high-performance liquid chromatography (HPLC). The effect of composition (from 5% to 80 v/v % of CH3CN) and рН (рН 2.7/6.0) of mobile phase, as well as temperature of chromatographic column (tc = 45/65 °C) on vitamins adsorption was studied. Nonlinear dependences of the sorbate retention factors on the acetonitrile content in the mobile phase are found out, indicating the variation of specific and non-specific interactions of vitamins with MSDN surface. Based on the obtained results, the conditions for chromatographic separation of the mixture of water-soluble vitamins in isocratic mode of HPLC on MSDN are optimized.