Aqueous Organic Media Research Articles

Stability of Monoterpene-Derived α-Hydroxyalkyl-Hydroperoxides in Aqueous Organic Media: Relevance to the Fate of Hydroperoxides in Aerosol Particle Phases.

The α-hydroxyalkyl-hydroperoxides [R-(H)C(-OH)(-OOH), α-HH] produced in the ozonolysis of unsaturated organic compounds may contribute to secondary organic aerosol (SOA) aging. α-HHs' inherent instability, however, hampers their detection and a positive assessment of their actual role. Here we report, for the first time, the rates and products of the decomposition of the α-HHs generated in the ozonolysis of atmospherically important monoterpenes α-pinene (α-P), d-limonene (d-L), γ-terpinene (γ-Tn), and α-terpineol (α-Tp) in water/acetonitrile (W/AN) mixtures. We detect α-HHs and multifunctional decomposition products as chloride adducts by online electrospray ionization mass spectrometry. Experiments involving D2O and H218O, instead of H216O, and an OH-radical scavenger show that α-HHs decompose into gem-diols + H2O2 rather than free radicals. α-HHs decay mono- or biexponentially depending on molecular structure and solvent composition. e-Fold times, τ1/e, in water-rich solvent mixtures range from τ1/e = 15-45 min for monoterpene-derived α-HHs to τ1/e > 103 min for the α-Tp-derived α-HH. All τ1/e's dramatically increase in <20% (v/v) water. Decay rates of the α-Tp-derived α-HH in pure water increase at lower pH (2.3 ≤ pH ≤ 3.3). The hydroperoxides detected in day-old SOA samples may reflect their increased stability in water-poor media and/or the slow decomposition of α-HHs from functionalized terpenes.

Cesium Lead Halide Perovskite Nanocrystals Prepared by Anion Exchange for Light-Emitting Diodes

Cesium lead halide perovskite nanocrystals (NCs) have emerged as a promising emitter for lighting and display technologies. However, the iodide-containing CsPb(Br/I)3 and CsPbI3 NCs suffer from chemical and phase degradation to nonfunctional orthorhombic (δ) phase. To address this challenge, we developed a facile synthetic protocol for halide exchange in pristine CsPbBr3 NCs. The protocol involves change in the nucleophilicity (or basicity) of the halide ions in aqueous–organic media which acts as the driving force to facilitate the halide exchange. Our method avoids the use of additives for anion solubilization, which otherwise induces chemical instability and quench the emission. The halide-exchanged CsPb(Br/I)3 and CsPbI3 NCs showed enhanced structural and optical properties, such as high phase stability and emission quantum yields up to 94.2%, as compared to the NCs (of same composition) obtained from direct synthesis. In addition, we demonstrated fabrication of light-emitting diodes (LED) based on ha...

Kinetics and Mechanism of the Hydrolysis of Benzyl Ether Bonds in Aqueous–Organic Media

Kinetic parameters (rate constant, energy of activation, and entropy of activation) of the acid-catalyzed hydrolysis of the benzyl ethers (3,4-dimethoxyphenyl)-(2-methoxyphenoxy)methane and (4-hydroxy-3-methoxyphenyl)methoxymethane are determined for a wide range of compositions for mixtures of water and organic solvents (dioxane, DMSO, and acetic acid). It is shown that the acid-catalyzed hydrolysis of these benzyl ethers in mixtures of water and aprotic solvents occurs as a reaction of bimolecular nucleophilic substitution. In aqueous acetic acid solutions, the mechanism of hydrolysis can be bimolecular or unimolecular, depending on the structure of the ether and the content of the organic solvent. The effect the solvents have on the rate and mechanism of the studied reaction is discussed in terms of solvation concepts.

Synthesis, Application, and Properties of Bis(1H-azol-1-yl)methanimines

The review considers methods of preparation and application of bis(1H-azol-1-yl)methanimines that are imino analogs of 1,1′-carbonylbisazoles widely used in the synthesis of various organic compounds, including natural ones. Methods of synthesis of a number of new symmetrical and unsymmetrical bisazolylmethanimines derived from imidazole, 2(4)-alkylimidazoles, and 1,2,4-triazole are described, and data on their hydrolytic stability in aqueous—organic medium (aqueous tetrahydrofuran) at 25°C and pH 7 and biological activity with respect to rat erythrocytes are given.

Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square‐planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single‐crystal X‐ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross‐coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.

PROMOTING EFFECT OF PYRIDINE BASES ON INDIRECT ELECTROCHEMICAL OXIDATION OF ALCOHOLS

The effect of pyridine on the reaction of indirect electrochemical oxidation of alcohols to carbonyl compounds by the catalytic system of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl - iodine in a two-phase aqueous-organic medium: methylene chloride - an aqueous solution of sodium bicarbonate (pH 8.6) was studed. It was shown that the process of indirect electrochemical oxidation of alcohols is accelerated by 1.5–2 times in the presence of pyridine. The corresponding aldehydes and ketones are formed with a high yield (75-95%) after passing 2-2.2 F of electricity. Additionally, the effect of other pyridine bases (2,6-lutidine, 4-acetylpyridine, 2-methyl-5-ethylpyridine, collidine) on indirect electrochemical oxidation of alcohols was studied using the example of 1-octanol. The absence of significant differences in the promoting action of pyridine bases was established and it was shown that in all cases the octanol is obtained with a high yield and coulombic efficiency (90-95 %). A mechanism for the reaction of indirect electrochemical oxidation of alcohols with the participation of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl and pyridine bases is proposed. The promoting effect of pyridine (or other pyridine bases) consists in the formation of an intermediate complex between the base, oxoammonium cation and alcohol. The formation of the complex facilitates the rapid transfer of the proton from the alcohol to the pyridine base and the hydride ion to the oxoammonium cation with the formation of the corresponding carbonyl compound from the alcohol. The preparative methods for the electrochemical synthesis of carbonyl compounds from aliphatic, cyclic, aromatic, heterocyclic alcohols including synthesis of 2,5-diformylfuran from 5-hydroxymethylfurfuralin using the two-phases catalytic system of 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl - potassium iodide in the presence of pyridine bases, are proposed.

Electrodeposition of corrosion-resistant Cr–P and Cr–P–W coatings from solutions based on compounds of trivalent chromium

Corrosion-resistant Cr–P and Cr–P–W coatings were obtained by electrodeposition from aqueous and aqueous–organic (DMF/water) solutions. The inclusion of phosphorus in the deposits formed on the cathode was confirmed using the EDX and XPS techniques. X-ray diffraction data revealed that co-deposition of phosphorus with chromium resulted in amorphization of the obtained coatings. It was shown that the incorporation of phosphorus into the coatings leads to the disappearance of the region of potentials corresponding to active metal dissolution as compared to Cr coatings. As a result, the coatings demonstrate higher corrosion resistance. Cracking of Cr–P coatings leads to a decrease in their protective ability with respect to steel. The impossibility of obtaining thick Cr–P layers by electrodeposition from aqueous solutions limits the sphere of their possible application. This problem was solved by electrodeposition of Cr–P–W coatings from aqueous–organic media. At coating thicknesses above 10 μm, fully penetrating pores in Cr–P–W coatings practically disappeared. The addition of tungsten to the composition of cathodic deposits resulted in an additional increase in their corrosion resistance.

Perimedine-linked rhodamine dye in visual sensing of Al3+, Fe3+ and Fe2+ ions in aqueous organic medium under different experimental conditions

ABSTRACTPerimedine labelled rhodamine dye 1 has been designed and synthesised. Metal ion binding studies of 1 have been performed in CH3CN/H2O (3:1, v/v, 10 mM Tris-HCl buffer, pH = 6.90). Compound 1 senses multiple metal ions such as Al3+, Fe3+ and Fe2+ by exhibiting turn on fluorescence and colour change (colourless to pink) under different experimental conditions. Concentration variation distinguishes Al3+ from Fe3+ ion. At low concentration (c = 1 x 10−4 M), only Al3+ ion can exhibit turn on fluorescence with sharp colour change. Sensing of Fe2+ ion through turn on fluorescence and colour change has been possible via in situ oxidation by following Fenton’s reaction.

Electrochemical active forms of metals ions in aqueous-organic media with high solvating ability. Part III. F-metals

Electrochemical active forms of metals ions in aqueous-organic media with high solvating ability. Part III. F-metals

Carbonization of the Modified Cellulose of Annual Crops

X-ray diffraction analysis was used to study the structural transformations of fibrous and microcrystalline flax, hemp, and jute cellulose, processed in aqueous-organic media containing sodium hydroxide. The thermal degradation of the initial and chemically modified cellulose was studied by thermogravimetry. The carbonization of cellulose in an inert atmosphere gave carbon materials. Common and specific features in the morphology and structure of the products were identified.

Kinetics and mechanism of sulfonylation of α-amino acids and dipeptides

The kinetics of sulfonylation of several α-amino acids: Gly, dl-α-Ala, dl-Val, dl-Leu, l-Ile, dl-Thr, dl-Met, dl-Ser, and l-Pro and dipeptides: Gly—Gly, l-α-Ala—l-α-Ala, l-α-Ala—β-Ala, β-Ala—β-Ala in water—propan-2-ol and water—1,4-dioxane binary systems were studied by spectrophotometry. The rate constants for reactions involving α-amino acids and dipeptides vary in a range for 81–52900 L mol–1 s–1 and 1.49–75 L mol–1 s–1, respectively. A considerable decrease in the rate constants for sulfonylation of dipeptides compared to those of corresponding α-amino acids suggests that the basicity of amino compounds has a signifi cant eff ect on their reactivity. The activation parameters of the reactions of amino acids and dipeptides with 3-nitrobenzenesulfonyl chloride in aqueous organic media were calculated. The mechanism of sulfonylation of α-amino acids and the Gly—Gly dipeptide was simulated by constructing the potential energy surfaces of the gas-phase reactions and taking into account the specifi c solvation of nucleophiles. The processes under study were shown to proceed by the SN2 mechanism, and the reaction pathway that corresponds to the nucleophilic attack along the near-axial direction is more favorable. It was found that the reactions of sulfonyl chlorides with solvated α-amino acids involve partial desolvation of α-amino acids occuring prior to the formation of activated complex.

A simple oxindole-based colorimetric HSO4¯ sensor: Naked-eye detection and spectroscopic analysis

Detection of hydrogen sulfate from an aqueous organic solvent systems medium attracts to lots of interest because of could be in most environmental and biological systems. In this study, the simple receptors 5 and 6 containing oxindole core were synthesized, and the anion sensing properties were studied using colorimetric, fluorometric detection and 1H-NMR spectroscopy. The research indicated that the specific ligand affinity for hydrogen sulfate ions results in drastic color and spectral changes. According to the data obtained, a new peak at 371 nm in the absorption spectrum of 5 and an increase in fluorescence intensity of 5 were observed in the presence of HSO4¯ ions. The binding ratio of 5 to HSO4¯ was calculated to be 1:1 according to Job's plot experiments. The Ks value was found to be 1.21×105 M−1 using the Benesi-Hildebrand equation. The LOD value was calculated with value as low as 8.9 μM for HSO4¯. Moreover, DFT calculations confirmed the nonplanar structures or propeller structures. As a result of all these studies, it can be said that 5 which is non-toxic, may be a useful and selective candidate turn-on sensor for HSO4¯ sensing in the industrial wastewaters.

Classification and Prediction of Sodium and Potassium Coronates Stability in Aqueous-Organic Media by Exploratory Data Analysis Methods

Linear Fisher classification functions, canonical linear discriminant functions, and trees (rules) for classification and prediction of the stability of sodium (18-crown-6Na+) and potassium coronates (18-crown-6K+) from the properties of aqueous-organic solvents (water—methanol, water—propan-2-ol, and water—acetonitrile) have been obtained basing on multivariate exploratory analysis. The proposed approach to prediction of the coronates stability has been verified using independent experimental data on the stability constants of sodium and potassium coronates in water—dioxane and water—acetone mixtures. The constructed classification functions and rules have possessed high predictive potential.

Theoretical and experimental studies on the conformational changes of organic solvent-stable protease from Bacillus sphaericus DS11 in methanol/water mixtures.

If natural proteases are used in organic synthesis, they are often inactivated or give a low rate of reaction in non-aqueous or aqueous-organic media. Therefore, to reveal the molecular mechanism governing the stability of proteases in organic solvents and increase protease stability in those systems is of intriguing interest. In the present study, the activity and conformational changes of an organic solvent-stable protease (OSP) from Bacillus sphaericus DS11 in different concentrations of methanol were investigated by measuring fluorescence, UV-Vis spectra, circular dichroism (CD), and conducting molecular dynamics (MD) simulations. The OSP expanded with increasing methanol concentration. The methanol molecules were able to enter into the OSP, leading to microenvironmental changes around the aromatic amino acids. More hydrophobic groups were exposed to the solvents at high methanol concentrations, and the original hydrophobic interaction in the protein decreased, thus resulting in the secondary and tertiary structure change in the OSP. Our results provide helpful insight into the molecular mechanism of the OSP tolerance to organic solvent and indicate directions for future work to design and engineer proteases that are stable at high organic solvent concentrations.

Synthesis and optical properties of AgInS2 nanoparticles

Ternary chalcogenide Ag-In quantum dots (QDs) are more environmentally friendly than known Cd-, Pb- and P-containing nanoparticles. Here we review the literature on colloidal synthesis methods, properties, and promising fields for the application of AgInS2 quantum dots. Similar to the QDs of lead and cadmium chalcogenides, the most accurate control over the structure and morphology of AgInS2 QDs is achieved by using the method of introducing precursors into high-boiling organic solvents. However, to realize the potential applications of ternary quantum dots, in particular as luminescent biomarkers, the quantum dots must be soluble in polar solvents, especially water. The transfer of quantum dots into aqueous solutions is usually accomplished by exchanging primary lyophilic ligands with smaller bifunctional molecules, such as thioglycolic (or mercapto­propionic) acids, which can passivate the surface of the quantum dots while making them soluble in the polar environment. Methods of colloidal synthesis of AgInS2 / ZnS quantum dots can be classified into the following types: Injection of ions into a high-boiling solvent Synthesis in a mixture of solvents Synthesis in the aquatic environment Methods for the synthesis of AgInS2 QDs in both aqueous solution and organic solvent medium are described. Examples of application of quantum dots for biomedical purposes and in photovoltaic and sensory devices are given. Quantum dots have high photostability and brightness, are characterized by a wide range of absorption and narrow spectral bands of radiation, ie meet most of the criteria for fluorescent materials and biosensors for imaging cancer cells in antitumor therapy, immunofluorescent labeling of proteins, detection of toxins s, visualize intracellular structures, etc. Quantum dots of tertiary chalcogenides, in particular CuInS2 and AgInS2, may be an alternative to quantum dots of binary lead and cadmium chalcogenides for use in light-emitting and light-absorbing systems, such as LEDs, sensors and solar absorbers.

Chromogenic and fluorogenic detection of copper ions in the solution and intracellular media

The development of a fluorescent sensor for the trace detection of the metallic contamination in the ecosystem and biological media have been a demand to reduce the health risk and environmental protection. Herein, we report the synthesis of 2‐formyl‐5‐picolinyl‐substituted rhodamine B derivative through Schiff base formation for the trace detection of the copper ions in the aqueous organic media as well as inside the live cells via bioimaging experiments. The ligand was successfully employed to detect the minute copper level ratiometrically through the chromogenic and fluorogenic response. The detection limit of the sensor was found to be 0.54 × 10−9 mol/L using 3 σ/slope relations. The reversible behavior of the ligand copper complex was determined using sulfide ions that regenerate the entire native properties of the ligands by snatching copper from the complex. The bioimaging experimental results represent the efficient membrane permeability of ligands with the minimum level of toxicity in the measured range found by the MTT assay. The appearance of bright red fluorescence from the BHK‐21 (hamster kidney fibroblast) cells upon treatment of the ligand incubated cells with the copper ions represents the utility of the proposed sensor for the copper detection probe in the intracellular media.

Effect of Nitrogen-Containing Bases on Oxidation of Ferrocenylboric and Ferrocenylcarboxylic Acids with Hydrogen Peroxide in Water and Water–Acetonitrile Mixed Solvent

The effect of triethylamine and pyridine on the kinetics and mechanism of ferrocenylboric and ferrocenylcarboxylic acids oxidation with hydrogen peroxide in water and aqueous-organic media has been studied. The addition of amines has accelerated the oxidation of ferrocenylboric acid both by hydrogen peroxide and by oxygen. Triethylamine has slowed down the oxidation of ferrocenylacetic acid and stabilized the formed zwitter-ion Fc+CH2COO–. Ferrocenylcarboxylic acid has not been oxidized by H2O2. The mechanism of the reaction has been suggested.

Time-resolved photoinduced charge dynamics of Cd chalcogenide-based materials

We have performed a comparative analysis of the photocharging dynamics of quantum dots (CdSe–CdS core–shell nanoparticles in toluene) and a bulk CdS single crystal by using time-resolved luminescence and transient grating techniques. The quantum dots were obtained through a colloidal synthesis method in aqueous–organic media with the average sizes of 2 nm and 2.9 nm. It has been shown that the relaxation of the photocharging dynamics in quantum dots is well fitted by the double-exponential decay function with time constants of a few and tens of picoseconds, which indicates that the energy loss of photoinduced charges is mainly the result of electron–phonon interaction.

Synthesis of new binary porphyrin–cyanine conjugates and their self-aggregation in organic-aqueous media

New amphiphilic conjugates of porphyrins and cyanine dye Cy5COOH were prepared by the creation of ester or amide bond between Cy5-carboxylic acid and hydroxy- or amino-substituted porphyrins. Study of self-aggregation of these conjugates in aqueous-organic media by dynamic light scattering and UV-VIS spectroscopy showed that the conjugates form micelles in THF–H2O with different ratios.

Catalyst-Free Oxytrifluoromethylation of Alkenes through Paired Electrolysis in Organic-Aqueous Media.

A mild, catalyst-free electrochemical oxytrifluoromethylation of alkenes has been developed. The procedure is based on the paired electrolysis of sodium triflinate and water in an undivided cell. Anodic oxidation of the triflinate anion generates trifluoromethyl radicals that react with the alkene. Water plays a dual role as oxidant for the cathode and nucleophile. The method has been utilized to prepare a diverse set of 1-hydroxy-2-trifluoromethyl compounds in moderate to excellent yields (27-94 %). Alcohols have also been tested as nucleophiles for this versatile method with moderate yields. Facile recycling of the electrolyte has been demonstrated, and application of electricity avoids the use of stoichiometric amounts of oxidizers in a safe and environmentally benign reaction.