Hexane Solution Research Articles

Cytochrome c-Cardiolipin Complex in a Nonpolar Environment.

Programmed cell death (apoptosis) plays an important role in the life of multicellular organisms and in the development of socially significant human diseases. Cytochrome c-cardiolipin complex (Cyt-CL) is formed at the very beginning of a cascade of apoptotic reactions. Nevertheless, the structure of the complex and the mechanism of its participation in lipid peroxidation in mitochondrial membranes are not yet understood. In previous work (Vladimirov, Y. A., et al. (2011) Crystallography, 56, 712-719), it was shown that the Cyt-CL complex precipitates in concentrated water solution, the sediment containing orderly nanospheres formed by cytochrome c molecules with changed conformation and surrounded by a cardiolipin monolayer, and they are essentially hydrophobic. In this work, we obtained chloroform and hexane solutions of Cyt-CL with lipid/protein ratio of 77 ± 11. The conditions are described under which the solutions were obtained. Study of the properties of Cyt-CL solutions in hydrophobic media will reveal their structure and the mechanism of their catalytic activity inside the lipid layer of biological membranes.

ChemInform Abstract: Lithium Insertion into Li2MoO4: Reversible Formation of (Li3Mo)O4 with a Disordered Rock‐Salt Structure.

AbstractCubic Li3‐xMoO4 is obtained by reaction of Li2MoO4 with BuLi in hexane solution (double or triple excess of BuLi).

Biocatalytic cascade reactions for asymmetric synthesis of aliphatic amino acids in a biphasic reaction system

Enantiopure aliphatic amino acids, including l-3-hydroxyadamantylglycine (l-Hag), l-tert-leucine (l-Tle) and l-norvaline, are essential chiral building blocks for a number of pharmaceutical drugs. Here, we developed cascade enzyme reactions in an extractive biphasic system using a branched-chain amino acid transaminase (BCTA) and an (S)-selective ω-transaminase (ω-TA) for asymmetric synthesis of the aliphatic amino acids from achiral α-keto acid precursors. The extractive cascade reactions enabled equilibrium shift of the BCTA reaction by recycling an amino acid cosubstrate as well as acceleration of the ω-TA reaction by removing an inhibitory ketone product from an aqueous phase. Starting with 20mM α-keto acid, 4mM rac-homoalanine and 50mM rac-α-methylbenzylamine (rac-α-MBA), the biphasic cascade reactions afforded synthesis of four unnatural amino acids (i.e., l-Tle, l-Hag, l-norvaline and l-norleucine) and two natural amino acids (i.e., l-valine and l-Leucine) with >92% conversion yield and >99.9% ee. To demonstrate the industrial feasibility of the extractive cascade reaction, preparative-scale synthesis of l-Hag was performed in a reaction mixture consisting of 300mL hexane and 50mL aqueous solution (50mM phosphate buffer, pH 7.0) charged with 50mM keto acid substrate, 5mM l-homoalanine, 120mM rac-α-MBA, 2U/mL BCTA and 16U/mL ω-TA. Conversion yield of l-Hag reached 92% with >99.9% ee at 70h. Product isolation led to 0.32g white solid of l-Hag (62 % isolation yield).

How Microsolvation Numbers at Li Control Aggregation Modes, sp(2)-Stereoinversion, and NMR Coupling Constants (2)JH,H of H2C═C in α-(2,6-Dimethylphenyl)vinyllithium.

The title compound 4 is a trisolvated monomer 4&3THF in THF solution and dimerizes endothermically to form (4&THF)2 with a strongly positive (!) dimerization entropy in toluene as the solvent. In the absence of electron-pair donor ligands, 4 aggregates (>dimer) in hydrocarbon solutions. These results followed from the (13)C-α splitting patterns and the magnitudes of the one-bond (13)C,(6)Li NMR coupling constants in combination with lithiation NMR shifts as secondary NMR criteria. The rate constants of cis/trans sp(2)-stereoinversion could be measured on the (1)H NMR time scale in THF, in which solvent the preinversion lifetime is 0.24 s at 25 °C. This inversion proceeds according to the pseudomonomolecular, ionic mechanism with the typical, strongly negative pseudoactivation entropy. In a different mechanism, the lifetimes are much longer at 25 °C for the dimer (4&t-BuOMe)2 in toluene (ca. 2.5 min) and for donor-free, aggregated 4 in hexane solution (roughly 1 min). The olefinic interproton two-bond coupling constants (2)JH,H of the H2C═CLi part are proposed as an indicator of microsolvation at Li, because they were found to increase linearly with the "explicit" solvation of α-arylvinyllithiums by 0, 1, 2, and 3 electron-pair donor ligands.

Batchwise extraction of methyl linolenate (18:3, ALA) from fatty acid methyl esters derived from soybean and canola oils using silver nitrate/silica gel

The incipient wetness impregnation (IWI) method was used to prepare a series of AgNO3/SiO2 adsorbents that were used for the extraction of unsaturated FAMEs from hexane solutions of methyl soyate and methyl canolate. The AgNO3/SiO2‐IWI adsorbents with the highest AgNO3 loadings (40 or 50% w/w) were the most selective for the removal of methyl linolenate (18:3). For example, extractions with 40% AgNO3/SiO2‐IWI reduce the amount of 18:3 from 7.0% in methyl soyate (1.00 mL) to 1.3% while extracting only 9% of the original FAMEs mixture. The extracted FAMEs fraction has a very high 18:3 (55.6%) and 18:2 (41.9%) composition. This adsorbent maintained its selectivity for 18:3 in at least four successive extractions. Similar extractions of methyl canolate yield a biodiesel that contains much smaller amounts of 18:3. The amounts of 18:3 and 18:2 that are extracted can be controlled by the AgNO3 loading and the amount of AgNO3/SiO2‐IWI that is used.Practical applications: Results of the reported studies show that AgNO3/SiO2 is able to preferentially remove methyl linolenate (18:3, ALA) from methyl soyate and methyl canolate. This batchwise process makes these biodiesels a source of the omega‐3 fatty acid ALA and gives a biodiesel that is less sensitive to oxidative deterioration.FAMEs derived from soybean and canola oils, when treated with AgNO3/SiO2, are separated into a portion that is enriched in 18:3 (ALA) and a biodiesel that contains the more saturated FAMEs.

Effect of phenolic compounds on photodegradation of anthracene and benzo[a]anthracene in media of different polarity

Abstract The photodegradation of anthracene (Ant) and benz[a]anthracene (BaA) were studied in air-equilibrated hexane, methanol and pure water solutions in the absence and presence of phenolic compounds (4-methylcatechol, guaiacol and syringol). In the absence of phenolic compound, the pseudo first-order degradation rate constants of Ant and BaA increased with the polarity of solvent, demonstrating the influence of solvent effects on the photoreactivity. The differences can be attributed to factors such as the proton donating potential of the solvent, and the formation potentials of PAH radical cation and hydroxyl radical in solvent. In the presence of phenolic compound, Ant and BaA photodegradation rates were accelerated in hexane and methanol while inhibited in water solutions. Photodegradation kinetics of the phenolic compounds were also measured; and visible colored products were observed in all three solvents. The observed accelerations of Ant and BaA photodecay in the presence of the phenolic compounds can be explained by energy transfer from the phenolic compound to PAH, phenolic hydrogen abstraction by excited PAH and more reactive radical formation from the phenolic compound. However, the inhibition effects of Ant and BaA photodecay in water were more influenced by the quenching of photo-produced reactive oxygen species (ROS) by the phenolic compound and/or its photoproducts. The results indicate that the photodegradation of PAHs will be highly dependent on the aerosol water content. i.e., the chemical composition of the environmental aerosols.

Volumetric, acoustic, and refractometric properties of (thiophene + hexane/cyclohexane) solutions in the presence of some imidazolium based ionic liquids at T = 298.15 K

Effective extraction of sulfur aromatic containing compounds from fuels by use of ionic liquids needs the knowledge and precise measurements of thermodynamic properties. In this work, effect of two types of the ionic liquids, 1-hexyl-3-methylimidazolium bromide [HMIM]Br, and 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM]EtSO4 on the thermodynamic properties of thiophene in hexane or cyclohexane solutions have been investigated. In this way, the densities, speeds of sound, and refractive indices of the solutions being studied have been measured at T=298.15K. These data have been used to calculate standard partial molar volumes Vϕ0, transfer partial molar volumes ΔtrVϕ0, partial molar isentropic compressibility κφ0, and molar refractions RD. The calculated parameters were used to discuss the manner of ionic liquid–thiophene interactions. Also, the scaled particle theory (SPT) was used to confirm and deep insight of results obtained from the calculated volumetric properties in terms of interaction volume Vint, and cavity volume Vcav.

Using Thiol Adsorption on Supported Au Nanoparticle Catalysts To Evaluate Au Dispersion and the Number of Active Sites for Benzyl Alcohol Oxidation

Two techniques to study the surface chemistry of supported gold nanoparticles were developed. First, phenylethyl mercaptan (PEM) adsorption from hexane solution was followed with UV–vis spectroscopy to evaluate the total amount of surface Au available. Two catalysts, Au/Al2O3 and Au/TiO2, were found to have Au:S surface stoichiometries of ∼2:1, whereas a Au/SiO2 catalyst had a Au:S surface stoichiometry of ∼1:1. The room temperature equilibrium binding constants for PEM adsorption on the Au/Al2O3 and Au/TiO2 catalysts were similar (∼3 × 105 M–1; ΔG ≈ −31 kJ/mol); the PEM–Au/SiO2 binding constant was somewhat larger (∼2 × 106 M–1; ΔG ≈ −36 kJ/mol). XPS data for all of the catalysts showed no observable changes in the Au oxidation state upon adsorption of the thiol. Implications of these experiments regarding self-assembled monolayers and thiol-stabilized Au nanoparticles are discussed. Second, kinetic titrations (i.e., controlled thiol-poisoning experiments) were developed as a method for evaluating the nu...

Solid-State Optical Properties and Crystal Structures of 1,4-Dipropoxy-9,10-anthraquinone Polymorphs

Abstract Recrystallization of 1,4-dipropoxy-9,10-anthraquinone from hexane solution afforded two polymorphs: red prisms and yellow needles. X-ray crystallographic analyses revealed that the molecular arrangement was an anti-parallel orientation for red solids and a slipped-parallel orientation for yellow solids. The difference in solid-state color was analyzed by TD-DFT calculations of their multimers.

Functionalization of cotton fiber by partial etherification and self-assembly of polyoxometalate encapsulated in Cu3(BTC)2 metal-organic framework.

A combination of a Keggin-type polyoxometalate (POM), [CuPW11O39](5-), with a Cu3(BTC)2 metal-organic framework (MOF-199/HKUST-1; where BTC is benzene-1,3,5-tricarboxylate), was successfully self-assembled on a cellulose substrate (cotton) with a room-temperature process. Cotton fibers were functionalized by partial etherification. Cu3(BTC)2 metal-organic framework and polyoxometalate encapsulated in Cu3(BTC)2 metal-organic framework were self-assembled on the carboxymethylate ion sites initiated with copper nitrate using ethanol and water as solvents. Octahedral crystals were observed on both MOF-cotton and POM-MOF-cotton; both contained copper while the POM-MOF-cotton also contained tungsten. Occupancy of POM in MOF cages was calculated to be about 13%. Moisture content remained at 3 to 4 wt % similar to that of untreated cotton. Reactivity to both hydrogen sulfide and methyl parathion was higher for POM-MOF-cotton due to the Keggin polyoxometalate and the extra-framework cations Cu(2+) ions compensating the charges of the encapsulated Keggins. The POM-MOF material was found to effectively remove 0.089 mg of methyl parathion per mg of MOF from a hexane solution while MOF-cotton removed only 0.054 mg of methyl parathion per mg of MOF.

Solution Behavior of Hyperbranched Polymethylsilsesquioxane with Intramolecular Cycles

Samples of hyperbranched polymethylsilsesquioxanes were synthesized at various polycondensation times and intramolecular cycle amounts. The samples were studied in solutions in toluene and hexane. It is shown that increasing the polycondensation duration results in the growth of number of cycles and intramolecular density that correlates with changes of molecular, hydrodynamic, and optic properties.

Lead selenide quantum dot polymer nanocomposites

Optical absorption and fluorescence properties of PbSe quantum dots (QDs) in an Angstrom Bond AB9093 epoxy polymer matrix to form a nanocomposite were investigated. To the authors’ knowledge, this is the first reported use of AB9093 as a QD matrix material and it was shown to out-perform the more common poly(methyl methacrylate) matrix in terms of preserving the optical properties of the QD, resulting in the first reported quantum yield (QY) for PbSe QDs in a polymer matrix, 26%. The 1-s first excitonic absorption peak of the QDs in a polymer matrix red shifted 65 nm in wavelength compared to QDs in a hexane solution, while the emission peak in the polymer matrix red shifted by 38 nm. The fluorescence QY dropped from 55% in hexane to 26% in the polymer matrix. A time resolved fluorescence study of the QDs showed single exponential lifetimes of 2.34 and 1.34 μs in toluene solution and the polymer matrix respectively.

Local structure analysis around the Nd center in a ternary catalyst comprising Nd(vers)3, Al((i)Bu)3 and Al((i)Bu)2Cl by XAFS.

Lanthanide-based catalysts are highly active for isoprene polymerization in hexane. In this paper, a ternary catalyst consisting of neodymium neodecanoate {Nd(vers)3}, Al((i)Bu)3 and Al((i)Bu)2Cl was studied by using X-ray-absorption fine-structure (XAFS) technique. A sealed and moisture-proof liquid sample cell with adjustable thickness was designed for Nd LIII-edge XAFS measurements. Based on the XAFS data analysis, detailed structure changes around the Nd center were obtained. It was found that the Nd(vers)3 molecules formed an oligomer structure in hexane solution with two Nd-O subshells (5O @ 2.39 Å and 5O @ 2.54 Å) around the Nd center. The alkylation process by adding Al((i)Bu)3 to the hexane solution of Nd(vers)3 partially destroyed the aggregation degree of Nd(vers)3 molecules in hexane solution. Al((i)Bu)3 ligands were bonded to the Nd center by Nd-C bonding. With the Nd : Al ratio increasing from 1 : 2.5 to 1 : 10, the O neighbors around Nd decreased from 4 to 2 but with an unchanged Nd-O bond length of 2.38 Å, and the C neighbors around Nd were kept at ca. 4 with Nd-C bond lengths in the range of 2.57-2.58 Å. The Nd-O bonds can be further replaced by Nd-C bonds during the aging process. The chlorination process by adding Al((i)Bu)2Cl to the mixture solution of Nd(vers)3 and Al((i)Bu)3 restrained intensively the agglomeration of Nd(vers)3 molecules in hexane solution. Al((i)Bu)2Cl ligands were bonded to the Nd center by Nd-Cl bonds. There were about 3-4 C neighbors at 2.58 Å, 2 Cl neighbors at 2.87 Å, and 2 Al next-neighbors at 3.14 Å around the Nd center. After allowing the ternary catalyst to stand for 5 days, the coordination numbers of Nd-C and Nd-Cl were all stabilized to 3 without bond length changes, and partial single Cl(-) anions were also bonded to the Nd center. All these structural details and their change tendency demonstrate that the decrease of aggregation degree of Nd(vers)3 molecules in hexane solution can improve the catalytic activity of the ternary lanthanide-based catalyst system.

On the nature of niobium substitution in niobium doped titania thin films by AACVD and its impact on electrical and optical properties

Niobium doped TiO2 thin films were deposited on silica coated glass substrate using aerosol assisted chemical vapour deposition (AACVD) from hexane solution, at 500 °C.

Influence of branching regularity on the behavior of hyperbranched polymers in solution

A carbosilane pseudo-dendrimer with irregular structure and degree of branching DB = 1 was synthesized and fractionated. The molar masses of the obtained fractions ranged from 5000 to 490 000 g mol−1. The hydrodynamic and conformational properties were studied by the methods of light scattering, sedimentation-diffusion analysis and viscometry in dilute hexane and toluene solutions. The Mark − Kuhn − Houwink dependences were obtained. The results for the pseudo-dendrimer are compared with the data for the initial hyperbranched poly(diallylcarbosilane) with DB = 0.5 and carbosilane dendrimer. It is shown that the solution properties of the pseudo-dendrimer are close to those for the irregular hyperbranched polymer and differ significantly from the dendrimer behavior. Hence, it is branching regularity rather than the degree of branching that determines the conformational and hydrodynamic properties of hyperbranched polymers with a high degree of branching DB ≥ 0.5. © 2014 Society of Chemical Industry

Thin Film Interfacial Cross-Linking Approach To Fabricate a Chitosan Rejecting Layer over Poly(ether sulfone) Support for Heavy Metal Removal

The formation of an ultrathin high performance chitosan rejection layer over a poly(ether sulfone) (PES) membrane support has been demonstrated in this study for its application in heavy metal removal by nanofiltration (NF). As a natural abundant resource, chitosan features advantages such as hydrophilicity and low cost. The aqueous chitosan solution was coated on the PES support first and partially dried in the fume hood for a certain period of time, before the introduction of hexane solution containing trimesoyl chloride (TMC) on its surface. The cross-linking reaction then took place immediately at the interface between hexane and water. The chitosan concentration and drying duration have been found to greatly affect the membrane morphology and performance. Comparisons with conventional water-soluble cross-linkers have revealed that the interfacial cross-linking by TMC is not only fast and time-saving, but also produces an ultrathin dense-selective layer of cross-linked chitosan with subnanometer pore sizes. As a result, a superior pure water permeability of 3.45 ± 0.25 L m–2 h–1 bar–1 and high salt rejections toward MgCl2, Pb(NO3)2, and NiCl2 have been achieved by the novel NF membrane, making it highly efficient for heavy metal removal.

Synthesis and Application of 1-(2-methyl-3-benzothienyl)-2-[3-methyl-2-thienyl]perfluorocyclopentene

A novel unsymmetrical photochromic diarylethene compound 1-(2-methyl-3-benzothienyl)-2-[3-methyl-2-thienyl] perfluorocyclopentene was designed and constructed successfully. Its optoelectronic properties have been discussed systematically, such as photochromic, fluorescence switch, kinetics experiments in hexane solution and PMMA. The consequences showed that this compound exhibited good reversible photochromism. The maxima absorption of compound closed-ring isomer 1c is 468nm. Upon irradiation with 297nm UV light, Its fluorescence intensity decreased along with the photochromism from open-ring isomers to closed-ring isomers upon irradiation with 297 nm UV light.

Synthesis and Properties of 1-(2-methyl-3-benzothienyl)-2-[2-methyl-5-(3-trifluoromethyl)-3-thienyl]perfluorocyclopentene

A novel asymmetrical photochromic diarylethene 1-(2-methyl-3-benzothienyl)-2-[2-methyl-5-(3-trifluoromethyl)-3-thienyl] perfluorocyclopentene was synthesized and its photochromic and fluorescent properties were also investigated. The compound exhibited remarkable photochromism, changing from colorless to red after irradiation with UV light and the open-ring isomer of the diarylethene 1 exhibited relatively remarkable fluorescence in hexane solution. The cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction.

Synthesis and Properties of 1-(3,5-dimethyl-4-isoxazole)-2-(2-methyl-(5-ethynyl)-3-thienyl)perfluorocyclopentene

A new photochromic diarylethene of 1-(3,5-dimethyl-4-isoxazole)-2- (2-methyl-(5-ethynyl)-3-thienyl) perfluorocyclopentene (1o) was synthesized. Its photochromic and fluorescence properties were investigated systematically. Upon irradiation with UV light with the extended response time, the diarylethene underwent a ring opening reaction to produce closed forms and color change in solution. The results showed the compound exhibited good photochromism in hexane solution. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene1oalso exhibited obviously fluorescence switches along with the photochromism.

An improved extraction method of rapeseed oil sample preparation for the subsequent determination in it of azole class fungicides by gas chromatography

The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed oil (or oil solution in hexane)/organic solvents has been studied at 20±1°C. The distribution constants (P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied pesticides are hydrophobic, i.e., in hexane–water system logP≫0. Replacement of water by organic solvents results in sharp logP falling, and their values become negative. It is revealed that solutions of strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in 50–2000 times for the majority of the studied pesticides. This phenomenon was used for the development of the improved technique for the quantitative analysis of a widely used azole class pesticides, which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate, and final GC–ECD (gas chromatography with electron capture detection) determination of azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below 10%. The obtained limits of quantitation, ranged from 3.0 to 300μgkg−1, are below the maximum residue levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully applied to different rapeseed oil samples.