Water Acetone Media Research Articles

Effects of Various Ripening Media on the Mesoporous Structure and Morphology of Hydroxyapatite Powders.

Mesoporous hydroxyapatite (HA) materials demonstrate advantages as catalysts and as support systems for catalysis, as adsorbent materials for removing contamination from soil and water, and as nanocarriers of functional agents for bone-related therapies. The present research demonstrates the possibility of the enlargement of the Brunauer-Emmett-Teller specific surface area (SSA), pore volume, and average pore diameter via changing the synthesis medium and ripening the material in the mother solution after the precipitation processes have been completed. HA powders were investigated via chemical analysis, X-ray diffraction analysis, Fourier-transform IR spectroscopy, transmission electron microscopy (TEM), and scanning (SEM) electron microscopy. Their SSA, pore volume, and pore-size distributions were determined via low-temperature nitrogen adsorption measurements, the zeta potential was established, and electron paramagnetic resonance (EPR) spectroscopy was performed. When the materials were synthesized in water-ethanol and water-acetone media, the SSA and total pore volume were 52.1 m2g-1 and 116.4 m2g-1, and 0.231 and 0.286 cm3g-1, respectively. After ripening for 21 days, the particle morphology changed, the length/width aspect ratio decreased, and looser and smaller powder agglomerates were obtained. These changes in their characteristics led to an increase in SSA for the water and water-ethanol samples, while pore volume demonstrated a multiplied increase for all samples, reaching 0.593 cm3g-1 for the water-acetone sample.

Solvent effect and Activation Parameters: A Kinetic Reaction of Ethyl Caprylate in Water-Acetone Media

The kinetic result of hydrolysis of Ethyl Caprlyate has been investigated at different composition of aqueous-organic solvent with Acetone (30-70% v/v) over the temperature range of 20 to 400c. The calculated result follows second order kinetics and is observed that the rate decreases with increasing proportion of Acetone. This behavior is attributed electrostatic nature that various solvent-solute interaction in reaction media. Linear plots of Logk against water concentration shows that equilibrium shifted from dense form to bulky form. Iso-kinetic temperature has been determined with the help of slopes of (ΔH*) versus (ΔS*). Thermodynamic parameter has been calculated with the help of Wynne-Jones and Eyring equation.

IONIZATION OF SOME NITROGEN-CONTAINING ORGANIC BASES IN WATER-ETHANOL AND WATER-ACETONE MEDIA

In this paper, the ionization constants (pKa) of some nitrogen-containing organic bases (morfoline, piperidine and benzylamine) in water-ethanol and water-acetone media at various concentrations of organic solvent in the system has been determined by the potentiometric titration method. It was established that the value of pKa of nitrogen-containing organic bases in aqueous-organic media naturally decreases with increasing content of organic solvent in the system. It was shown that their nature (aromatic or heterocyclic) and the physico-chemical properties of the medium are significantly influenced by the nature and degree of change in the electron donor ability of the nitrogen-containing organic bases studied It should be noted that for the studied nitrogen-containing organic bases (morfoline, piperidine and benzylamine), when passing from an aqueous medium to an organic one (ethanol or acetone), the pKa values naturally decrease with an increase in the content of the organic solvent in the system. In general, in the transition from an aqueous medium to an organic one (ethanol or acetone), a change in pKa can reach 2.43 units. It was established that the dependence of the values of pKa of nitrogen-containing organic bases which were determinate via potentiometric titration method on the inverse of the dielectric constant of water-ethanol and water-acetone solutions tends to be linear, consistent with Izmailov’s theory. Thus, we can conclude that the change in the ratio of the mixed solvent components and, as a result, in general, dielectric permeability of the medium does not lead to a significant change in the solvation characteristics of the nitrogen-containing organic bases studied.

THE ELECTRON DONATING PROPERTIES OF NITROGENCONTAINING ORGANIC BASES IN WATER-ETHANOL AND WATER-ACETONE SOLUTIONS

In this paper, the dissociation constants (pKa) of some nitrogen-containing organic bases (aniline, pyridine and octylamine) in water-ethanol and water-acetone media at various concentrations of organic solvent in the system has been determined by the potentiometric titration method. It was established that the value of pKa of nitrogen-containing organic bases in aqueous-organic media naturally decreases with increasing content of organic solvent in the system. It was shown that their nature (aliphatic, aromatic, heterocyclic) and the physicochemical properties of the medium are significantly influenced by the nature and degree of change in the electron donor ability of the nitrogen-containing organic bases studied. It was noted that for aniline in water-ethanol solutions in the transition from water to an organic solvent, the value of pKa does not change much (ΔpKa = 0,9), while for pyridine and octylamine these changes are significant, and the values of ΔpKa are 2,9 and 1,7, respectively, which can be explained by the specific solvation of the aniline amino group with ethanol. In the case of water-acetone solutions, the behavior of the nitrogen-containing organic bases was studied generally similar, and the values of ΔpKa are within the range of 1,7-2,6. It was established that the dependence of the values of pKa of nitrogen-containing organic bases on the inverse of the dielectric constant of water-ethanol and water-acetone solutions tends to be linear, consistent with Izmailov’s theory. Thus, we can conclude that the change in the ratio of the mixed solvent components and, as a result, in general, dielectric permeability of the medium does not lead to a significant change in the solvation characteristics of the nitrogencontaining organic bases studied.

A simple synthesis and characterization of binary Co 0.5Fe 0.5(H 2PO 4) 2·2H 2O and its final decomposition product CoFeP 4O 12

This paper reports the synthesis of binary Co 0.5Fe 0.5(H 2PO 4) 2·2H 2O by a simple, rapid and cost-effective method using CoCO 3–Fe(c)–H 3PO 4 system in water–acetone media at ambient temperature. Thermal transformation of the synthesized powder was investigated by TG/DTG/DTA and DSC techniques, which indicate that its final decomposed product was a binary cobalt iron cyclotetraphosphate CoFeP 4O 12. The FTIR and XRD results of the synthesized Co 0.5Fe 0.5(H 2PO 4) 2·2H 2O and the decomposed CoFeP 4O 12 indicate the pure monoclinic phases with space group P2 1/n and C2/c, respectively. The morphologies of Co 0.5Fe 0.5(H 2PO 4) 2·2H 2O and CoFeP 4O 12 powders appear non-uniform particle shapes and high agglomerates, which are different from the cases of the single compounds M(H 2PO 4) 2·2H 2O and M 2P 4O 12 (where M = Co, Fe). The magnetic properties of the studied compounds are superparamagnetic behaviors, which are important for specific applications. The physical properties of the studied powders are comparable with those reported in our previous study, affected by medium and condition of preparation method.

Facile synthesis of B-MCM-41 with controlled morphologies using water–acetone media

B-MCM-41 nanoparticles with controlled morphologies including nanorods and nanospheres have been synthesized in water–acetone media using cetyltrimethylammonium bromide (CTAB) as the template and boric acid as boron source. It was found that the total boron content in the product increases with reducing both the water-to-acetone molar ratios in the synthesis gel and hydrothermal temperature. The framework boron content rises with the increase in the hydrothermal temperature. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the long axis in major areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these boron-containing mesoporous silicas.

Facile synthesis of mesoporous silica nanoparticles with controlled morphologies using water–acetone media

Mesoporous silica nanoparticles with controlled morphologies including nanococoons, nanorods and nanospheres have been synthesized in water–acetone media at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained nanoparticles generally show hexagonal-like mesoporous structures with average pore size ranging from 2.7 to 3.3 nm and surface area from 806 to 1055 m 2/g, respectively. It was found that the changes in water-to-acetone molar ratios have a dramatic impact on the morphologies of the mesoporous silica with different surface roughness, probably due to the solvent influence on the rate of the hydrolysis of tetraethoxy silane (TEOS) and the polymerization of inorganic species. Interestingly, the morphology of the mesoporous silica products can be controlled in shape from nanococoons to nanorods to nanospheres just by decreasing the water-to-acetone molar ratio from 75 to 30 to 15, respectively. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the short axis in some areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these mesoporous silicas.

A highly efficient method of epoxidation of olefins with hydrogen peroxide catalyzed by changeable hexadentate 8-quinolinolato manganese(III) complexes

Novel hexadentate binding 8-quinolinolato manganese(III) complexes were proposed and conveniently synthesized for the epoxidation of olefins with aqueous hydrogen peroxide in water–acetone media with ammonium acetate and acetic acid as additives. The catalytic efficiencies of the suggested catalysts were found to be obviously superior to the traditional tetradentate salen–Mn IIICl, due to their special hexadentate binding structures that could be easily converted to the corresponding pentadentate with pendant hydroxyl groups by opening an axial Mn O bond in the reaction media, as supported by UV–vis spectra, in situ cyclic voltammetry, and quartz crystal microbalance characterizations.

Water–acetone Media Enforced Chemoselective Synthesis of 2-substituted Pyrrole Stable Phosphorus Ylides from Reaction between Pyrrole and Acetylenic Esters in the Presence of Triphenylphosphine

Pyrrole undergoes a smooth reaction with dialkyl acetylenedicarboxylates in the presence of triphenylphosphine in a mixture of water–acetone (50:50) as a solvent pathway to produce phosphorus ylides of 2-substituted pyrrole in good yield.

Swelling and collapse of the gel composites based on neutral and slightly charged poly(acrylamide) gels containing Na-montmorillonite

Abstract Clay-polymer hydrogel composites were prepared on the basis of neutral and slightly charged cationic and anionic poly(acrylamide) gels containing different amounts of the clay mineral Na-montmorillonite. The swelling and collapse in water–acetone media and the mechanical behavior of such gels were studied. It is shown that the clay incorporated into neutral poly(acrylamide) gel hardly influences its degree of swelling in water. On the other hand, for the anionic and especially for the cationic gels, the swelling in the presence of clay decreases. The elastic modulus of gels with incorporated clay is higher, while the amplitude of the acetone-induced collapse is lower than for the corresponding pure gel systems.

Mechanism of the Formation of Organic Derivatives of gamma-Zirconium Phosphate by Topotactic Reactions with Phosphonic Acids in Water and Water-Acetone Media.

The rates of the topotactic reactions between gamma-zirconium phosphate and phenylphosphonic acid in water and water-acetone mixtures at various temperatures were investigated. The slow rates of the process in aqueous medium or in water-acetone mixtures at temperatures lower than 50 degrees C were attributed to a slow interdiffusion of O(2)P(OH)(2)(-) and O(2)P(OH)(C(6)H(5))(-) groups in the interlayer region of gamma-ZrP. Similar to ion-exchange processes, the replacement begins in the external part of the interlayer region and progresses toward the central region with the formation of an advancing phase boundary. In water-acetone mixtures at temperatures higher than 60 degrees C an exfoliation of gamma-ZrP was found. Thus, the initial process is very fast since the substitution can take place directly on the surface of the exfoliated gamma-lamellae. However, after a certain degree of substitution, a flocculation of the colloidal dispersion, which slows down the rate of the further topotactic substitution, was observed. Some considerations on the topotactic substitution occurring on the surface of the exfoliated lamellae and on the mechanism of the diffusion of the exchanging species in the interlayer region are also reported.

Polarography of phthalic anhydride molecule in water-acetone media

Polarography of phthalic anhydride molecule in water-acetone media

The dielectric constant and salt effects upon the acid hydrolysis of ethyl formate

The hydrolysis of ethyl formate catalysed by hydrochloric acid was studied at three temperatures in water-acetone media and in water media containing different concentrations of sodium nitrate. The effect of various ionic strengths and dielectric constants upon the rate of acid hydrolysis of ethyl formate is presented from the point of electrostatics and the results were compared to like effects upon the acid hydrolysis of ethyl acetate and methyl propionate. Neither the dielectric constant effect nor the salt effect lends itself readily to theoretical interpretation. It was assumed that a partial explanation of these anomalous results might be in the extrapolation of the acid radical to the simplest carboxylic acid. This suggestion was supported somewhat by the trends towards less adherance to the electrostatic theory at certain temperatures in the series methyl propionate, ethyl acetate and ethyl formate.

The dielectric constant and salt effects upon the acid hydrolysis of methyl propionate

The hydrolysis of methyl propionate catalyzed by hydrochloric acid has been studied at three temperatures in water-acetone media and in water media containing different concentrations of sodium nitrate. The specific velocity constants in wateracetone media were shown to conform to the theory for reaction between positive ions and dipolar molecules. bender's mechanism for ester hydrolysis has been accepted as plausible in view of the kinetics in mixed media. The specific velocity constants in the sodium nitrate solutions were shown to conform to the theory of Euler.