Nonpolar Organic Solvents Research Articles

Role of Oxygen and Effect of Solvents on Nematogens—A Computational Analysis

A comparative computational analysis on two nematogens, p-n-heptylbenzoic acid (7BAC), and p-n-heptyloxybenzoic acid (7OBAC) has been carried out with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation theory with the multicentered–multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4) and chloroform (CHCl3) at room temperature (300 K). The most stable configuration of pairing, during the stacking interactions, has been obtained for 7BAC in CCl4. Furthermore, an attempt has been made to analyze the role of oxygen and effect of solvents on nematogens at molecular level.

Design and synthesis of lipase nanogel with interpenetrating polymer networks for enhanced catalysis: Molecular simulation and experimental validation

Abstract A temperature-responsive lipase nanogel (denoted as CRL-IPN nanogel), in which lipase is encapsulated into an interpenetrating polymer matrix formed by polyacrylamide and poly(N-isopropylacrylamide) (PNIPAAm) has been designed and synthesized for an enhanced stability and activity in both aqueous and non-polar organic solvents. A three-step method, including acryloylation, polymerization with acrylamide and sequential polymerization with N-isopropylacrylamide, was established to fabricate enzyme nanogel with temperature-sensitive interpenetrating polymer network. It has been shown by an all-atom molecular dynamics simulation that above mentioned polymer matrix forms a more hydrophobic environment, as compared to that obtained with sole polyacrylamide, because of the penetration of N-isopropylacrylamide into the polymer acrylamide network via hydrogen bonding, which is further confirmed by the fluorescence spectrum. This favours the uptake of hydrophobic substrates and thus the overall rate of enzymatic catalysis. The enhanced stability and catalytic performance of this novel lipase nanogel in aqueous and non-polar organic solvent were demonstrated by using hydrolysis reaction of p-NPP in aqueous and esterification reaction of ibuprofen in isooctane. In aqueous solution, the residual activity of CRL-IPN nanogel maintains its 70% activity at 60 °C after 4 h, compared with that free lipase only has 30% at the same condition. In addition, the CRL-IPN nanogel can be reused for 10 cycles with no loss of its activity. In isooctane, CRL-IPN nanogel gave a 33% yield of esterification of ibuprofen, in comparison to 22% using free lipase and less than 5% using lipase encapsulated in a polyacrylamide matrix. The enhanced stability and activity make this CRL-IPN nanogel promising for enzymatic catalysis in non-polar solvents.

In silico studies of 1,3(R):2,4(S)‐dibenzylidene‐D‐sorbitol as a gelator for polypropylene

The organic gelator 1,3(R):2,4(S)‐dibenzylidene‐D‐sorbitol (DBS) self‐organizes to form a 3‐D network at relatively low concentrations in a variety of nonpolar organic solvents and polymer melt. In this work, we have investigated the interactions between DBS molecules in polypropylene (PP) by molecular modeling. We have used quantum mechanics to elucidate the preferred geometry of one molecule and a dimer of DBS, and molecular mechanics and molecular dynamics to simulate pure DBS, pure PP, and mixture of DBS and PP as condensed phases, at various temperatures. It was found that inter‐ and intramolecular H‐bonds between DBS molecules are formed in PP in a much more pronounced manner than those formed in pure DBS. The most significant intermolecular H‐bonds are formed between the terminal hydroxyl groups. The most significant intramolecular H‐bonds are formed between O5 /H‐O6 groups. Due to the H‐bonds, DBS molecules form a rigid structure similar to liquid crystal forming molecules, which might explain their tendency to create nanofibrils. It seems that the aromatic rings do not contribute significantly to the intermolecular interactions. Their main role is probably to stiff the molecular structure. Temperature dependences of inter‐ and intramolecular interactions are different. Whereas intermolecular interactions peak heights decrease when temperature increases for pure DBS, the intramolecular interaction almost does not change. Copyright © 2012 John Wiley & Sons, Ltd.

Novel polyelectrolyte gels as absorbent polymers for nonpolar organic solvents based on polymerizable ionic liquids

Novel class of polyelectrolyte gels based on the copolymer of vinylimidazolium-typed ionic liquid monomer and Dodecyl methacrylate was prepared by free radical polymerization. A small amount of 3-n-Dodecyl-1-vinylimidazolium tetrafluoroborate is incorporated into crosslinked polyacrylates to provide new lipophilic polyelectrolyte gels that evaluated for swelling in less-polar and nonpolar organic solvents. Their swelling degree becomes more than 50 times as much as their dried weights in some organic solvents. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated. The present absorbents are expected to find practical applications particularly in the recovery of spilled oils and the treatment of waste water.

Ionic Polymers Act as Polyelectrolytes in Nonpolar Media.

Polyelectrolytes are ubiquitous materials, and their unique properties originate from dissociation of ionic groups to the small number of macromolecular ions and the large number of small counterions. They have been exploited only in water or high-dielectric media and scarcely in nonpolar ones (ε < 10). Herein, we demonstrate that poly(octadecyl acrylate) bearing tetraalkylammonium tetraarylborate as ionic groups behaves as a polyelectrolyte in the common nonpolar organic solvents such as chloroform, THF, and 1,2-dichloroethane. Conductivity measurement, DOSY NMR spectroscopy, and viscosity measurements clearly indicate that they form the extended conformation in them. This result emphasizes that the ionic polymers bearing suitable ion pairs ionizable in the given media act as polyelectrolytes. Various characteristic properties and processes of polyelectrolytes should be realized in nonpolar media by designing ion pairs and polymer chains in the ionic polymers. Moreover, our results imply that electrostatic interaction is readily available as a long-range repulsive force even in the nonpolar media.

Synthesis, structural analysis and solvatochromic behaviour of 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile mesogen

In this communication, we report the synthesis and characterisation of a new luminescent liquid crystalline material, 4,6-bis (4-butoxyphenyl)-2-methoxynicotinonitrile (3). We have confirmed its structure by Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy, elemental analysis and X-ray single crystal diffraction studies. The newly synthesised compound crystallises in a monoclinic system with the space group C2/c and its cell parameters are found to be a = 25.181(4) Å, b = 15.651(4)Å, c = 12.703(19) Å, V = 4880.4 (16) Å, Z = 8. The results indicate that the presence of weak CH … O and CH … N hydrogen bonding as short-range intermolecular interactions are responsible for the formation of its crystal assembly. The measured torsion angle shows the existence of a distorted structure for the molecule wherein 4-butoxyphenylene ring substituent at the fourth position of the central pyridine ring forms a torsion angle χ[C(4), C(3), C(10), C(19)] of 40.55°. Its liquid crystalline behaviour was investigated with the aid of polarised optical microscopy and differential scanning calorimetry. The study reveals that the compound displays a broad nematic phase in the range of 78–112°C. Further, solution phase optical studies indicate that it is a blue light emitter in different non-polar and polar organic solvents at a concentration of 10−5M.

Alteraciones del metabolismo de las lipoproteínas

Lipids are a heterogenic group of soluble particles in non-polar organic solvents and insolubility in water. They circulate in plasma assembled with apoproteins to form lipoproteins. Lipid metabolism is divided in exogenous and endogenous pathways. Exogenous pathway metabolizes diet fats, being chylomicrons the most important particles. In endogenous pathway liver releases VLDL, which is transformed in IDL and LDL. In reverse cholesterol transport, cholesterol is transferred to HDL from peripheral tissues to the liver. This is a paramount antiatherogenic process.LDL are the most important atherogenic plasma particles, and HDL the most important antiatherogenic particles. Lipoprotein (a) is considered an independent cardiovascular risk factor. In patients with intermediate or high cardiovascular risk is recommended screening for lipoprotein (a).

High cell density cultivation of Pseudomonas putida strain HKT554 and its application for optically active sulfoxide production

Culture conditions with Pseudomonas putida strain HKT554, expressing naphthalene dioxygenase, known as the biocatalyst showing wide substrate specificity, were optimized for high cell density cultivation (HCDC). Culture in a medium TK-B modified from that for HCDC of Escherichia coli with glucose fed-batch and dissolved oxygen stat resulted in a high cell density growth of 114 g dry cell/l at 40 h of cultivation. This system was further applied for S-(+)-methyl phenyl sulfoxide (MPSO) production from methyl phenyl sulfide. Addition of nonpolar organic solvent, such as n-hexadecane, greatly enhanced the MPSO production due to the prevention of substrate evaporation, resulting in a MPSO production up to 39 mM in 30 h with a conversion rate of 95.7 mol%.

Construction of Chlorosomal Rod Self‐Aggregates in the Solid State on Any Substrates from Synthetic Chlorophyll Derivatives Possessing an Oligomethylene Chain at the 17‐Propionate Residue

Chlorosomes are one of the most unique natural light-harvesting antennas and their supramolecular nanostructures are still under debate. Chlorosomes contain bacteriochlorophyll (BChl)-c, d and e molecules and these pigments self-aggregate under a hydrophobic environment inside a chlorosome. The self-aggregates are mainly constructed by the following three interactions: hydrogen bonding, coordination bonding and π-π stacking. Supramolecular nanostructures of self-aggregated BChls have been widely investigated by spectroscopic and microscopic techniques. Model compounds of such chlorosomal BChl molecules have been synthesized and the effects of esterified long alkyl chains at the 17-propionate residue for their self-aggregation have been studied. Structurally simple zinc chlorophyll derivatives possessing an oligomethylene chain as the esterifying group at the 17-propionate residue were prepared as chlorosomal BChl models. The synthetic zinc BChls self-aggregated in nonpolar organic solvents to give precipitates. The resulting insoluble self-aggregated solids were investigated on a variety of substrates, including hydrophobic, neutral and hydrophilic substrates, by visible absorption, circular dichroism and polarized light absorption spectroscopies, as well as atomic force, transmission electron and scanning electron microscopies. The self-aggregates of synthetic Zn-BChls formed rods with an approximately 5 nm diameter and wires with further elongated growth of the rods (aspect ratio >200). The diameter size was consistent with that estimated for natural chlorosomal rods in a filamentous anoxygenic phototroph, Chloroflexus aurantiacus. The supramolecular formation and stability of the rod on the examined substrates depended on the length of an oligomethylene chain at the 17-propionate residue as well as on the surface properties. Especially, the number of the 5 nm rods on the substrates increased with an elongation of the chain.

Conventional and microwave-assisted synthesis of hyperbranched and highly branched polylysine towards amphiphilic core–shell nanocontainers for metal nanoparticles

Hyperbranched amphiphilic polymeric systems with core–shell architecture can be used as versatile nanocontainers and templates with great potential in application fields ranging from medicine to organic coatings. In order to explore an alternative to the already widely used and established synthetic macromolecules, we synthesized new polymers based on hyperbranched polylysine. Polylysine was prepared with classical heating and microwave-assisted heating, respectively. While, the synthesis at 160 °C resulted in hyperbranched polylysine with degrees of branching (DB) between 0.50 and 0.54, the microwave-assisted heating at 200 °C resulted in highly branched polymers with DB values of 0.30–0.32. The molecular weight Mn could be controlled in a range of 5000–12,000 g/mol. The hyperbranched polylysine was hydrophobized via polymer-analogue reactions using a mixture of stearoyl/palmitoyl chloride and glycidyl hexadecyl ether, respectively. These reactions yielded in high degrees of modification (80% and 90%, respectively). The synthesized polymers are soluble in non-polar organic solvents, such as toluene and chloroform, and take up metal salts to up to 25 wt.%. They support the formation of Ag, Au, and Pd nanoparticles and nanocrystals in organic solvents and stabilize them. Thus, the here presented macromolecules are a promising readily achievable alternative to existing core–shell systems.

One-pot synthesis of gold nanoparticles densely coated with nitroxide spins

We describe a new and simple method for one-pot synthesis of gold nanoparticles of spherical shape densely coated with unpaired electrons. The gold nanoparticles have a narrow size distribution (1.90±0.54nm) and even coverage of nitroxide spins per particle and are soluble both in non-polar and polar organic solvents. The one-pot synthesis consists of direct grafting of nanoparticles by ligand substitution with an in situ generated bisnitroxide radical-containing thiol nucleophile. The obtained nanoparticles are stabilized by two types of ligands: covalently attached nitroxide radicals and tetraoctylammonium bromide ions pairs weakly bound to the gold surface. The average number of ligands per core was derived from X-ray photoelectron spectroscopy (XPS) as well as from thermogravimetric and bromine concentration analyses. The proposed procedure can be a powerful tool for the preparation of spin-labeled gold nanoparticles soluble in non-polar and polar organic solvents which should be useful for applications in various fields including biochemistry, catalysis and electrochemistry.

Direct lipid extraction from wet Chlamydomonas reinhardtii biomass using osmotic shock

High-cost downstream process is a major bottleneck for producing microalgal biodiesel at reasonable price. Conventional lipid extraction process necessitates biomass drying process, which requires substantial amount of energy. In this regard, lipid extraction from wet biomass must be an attractive solution. However, it is almost impossible to recover lipid directly from wet microalgae with current technology. In this study, we conceived osmotic shock treatment as a novel method to extract lipid efficiently. Osmotic shock treatment was applied directly to wet Chlamydomonas reinhardtii biomass with water content >99%, along with both polar and non-polar organic solvents. Our results demonstrated that osmotic shock could increase lipid recovery approximately 2 times. We also investigated whether the presence of cell wall or different cell stages could have any impact on lipid recovery. Cell wall-less mutant stains and senescent cell phase could display significantly increased lipid recovery. Taken together, our results suggested that osmotic shock is a promising technique for wet lipid extraction from microalgal biomass and successfully determined that specific manipulation of biomass in certain cell phase could enhance lipid recovery further.

Solvent Effects on Phase Stability of a Nematogen—A Molecular Level Approach

The phase stability of a nematogen 4′-n-pentyloxy-4-biphenylcarbonitrile (POCB) has been studied with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger Perturbation theory along with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), benzene (C6H6), and chloroform (CHCl3) at room temperature (300 K). A comparison among the different solvents has been made to analyze the solvent effects. The most stable configuration has been obtained in CCl4 during the stacking interactions. This provides a new and attention-grabbing molecular model for nematogen in nonpolar organic solvents.

Synthesis of water-soluble luminescent LaVO4:Ln3+ porous nanoparticles

Water-soluble luminescent Eu3+ and Tb3+-doped LaVO4 porous nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD), Field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, UV/Vis absorption, and photoluminescence spectroscopic techniques were employed to characterize the structure and morphology of as-prepared products. The results of the XRD confirm the formation of well-crystallized LaVO4 phase with a tetragonal zircon structure. The TEM images illustrate that the as-formed Eu3+ and Tb3+-doped LaVO4 nanoparticles have irregular spherical shape, hairy nanoporous structures with an average particle size 50–130 nm. These nanoparticles were well-dispersed in polar and non-polar organic solvents to form clear colloidal solutions. The colloidal solutions of Eu3+ and Tb3+-doped zircon-type LaVO4 nanoparticles show the most dominant characteristic emissions (hypersensitive transitions) of Eu3+ at 615 nm (5 D 0 → 7 F 2) and Tb3+ at 543 nm (5 D 4 → 7 F 5), respectively, as the result of an energy transfer from the VO4 3− to luminescent metal ions activators. Compared with other-shape nanocrystals, the luminescence intensity of the irregular hairy spherical porous-like nanoparticles are obviously enhanced. It therefore, suggests that we could obtain function-improved materials by tailoring the size and shape of the LaVO4:Ln3+ nanostructures that are very suitable for use in biological applications, such as protein-labeling, drug delivery, and fluorescent bioprobes.

Hexane Fraction of American Ginseng Suppresses Colitis and Colon Cancer—Response

We wish to thank Drs. Chan and Huff for pointing out their elegant toxicology and carcinogenicity studies on Panax ginseng (1, 2). We are happy to see that such a high dose of P. ginseng (1, 2) is nontoxic and noncarcinogenic in both short- and long-term studies. Doses used in the studies of Chan and colleagues (1, 2) were 0; 1,250; 2,500; or 5,000 mg/kg body weight of ginseng in sterile water administered 5 d/wk by oral gavage. Comparatively, we used 11.93 mg/kg body weight of American ginseng (AG) or hexane fraction of AG (HAG; refs. 3–5), which is 100 to 400 times less than what was used by Chan and colleagues (1, 2). From the study conducted by Dr. Chan and colleagues, the oral LD50 dose of P. ginseng was reported to be more than 5,000 mg/kg for mice (1, 2). In a separate study, reported in the literature of RTECS 1998 (6), the oral LD50 dose for mice was 200 mg/kg of P. ginseng. Based on these separate observations, Dr. Chan and colleagues pointed out that these changes in the oral LD50 dose of P. ginseng for mice could be due to the use of different ginseng preparations or strains of test animals used in these separate studies (1). Although such observations make it difficult to compare directly the physiologic and toxicologic effects of AG/HAG and P. ginseng, the general consensus between both studies is that AG/HAG are only toxic at levels far above that shown to succeed in suppressing colitis and colon cancer in mice. To this end, we must point out that we used AG (Panax quinquefolius) extracted with 80% aqueous ethanol compared with P. ginseng (extracted with 75% aqueous ethanol) used in the studies conducted by Chan and colleagues (1, 2). In addition, we conducted bioassay-guided fractionation of P. quinquefolius with a nonpolar organic solvent; hexane to extract the lipid soluble components of AG (HAG). In conclusion, we thank Drs. Chan and Huff for directing the readers to their article and such complementary studies drive home the understanding that ginseng can suppress chronic inflammatory diseases such as colitis with no toxic side effects. However, this is only shown in mice but supports the hypothesis that ginseng may suppress colitis and prevent colon cancer in humans.See the original Letter to the Editor, p. 982No potential conflicts of interest were disclosed.

Polyoxometalate–Organic Hybrid Molecules as Amphiphilic Emulsion Catalysts for Deep Desulfurization

So emulsional: Two hexavanadate-organic hybrids were synthesized and their amphiphilic properties were confirmed by forming emulsions in mixtures of water and nonpolar organic solvents, and were utilized as "emulsion catalysts" in deep desulfurization reactions (see figure). Their catalytic activities show a pH-dependent behavior, which can be explained by the size-change of emulsions and the appearance of reverse emulsions.

Entrainer Effects on Enantiodifferentiating Photocyclization of 5-Hydroxy-1,1-diphenylpentene in Near-Critical and Supercritical Carbon Dioxide

Enantiodifferentiating photocyclization of 5-hydroxy-1,1-diphenyl-1-pentene (1) sensitized by bis(1,2;4,5-di-O-isopropylidene-α-fructopyranosyl) 1,4-naphthalenedicarboxylate (2) was performed in near-critical and supercritical carbon dioxide media containing organic entrainers to obtain a chiral tetrahydrofuran derivative (3) in enantiomeric excess (ee) higher than those obtained in conventional organic solvents. Interestingly, the entrainer-driven ee enhancement did not depend on the entrainer polarity, which is in contrast to the behavior of the ee observed upon selective solvation in nonpolar organic solvents. This indicates that entrainer clustering around the intervening exciplex is essential in order to keep the intimate sensitizer-substrate contact within the exciplex. Therefore, the clustering itself, rather than its property, is more crucial to prevent the dissociative diffusion to gaseous CO(2). The wider allowance in choosing the entrainer enables us to use more "green" solvents for achieving the ee enhancement, while reducing the environmental risk.

Characterization of stable hydrophobic carbon coating and its application in removing organic pollutants

Polydimethylsiloxane (PDMS) thin films were deposited on Ni particles with a mean size of ∼1 μm using chemical vapor deposition method. The thin films consisting of these PDMS-covered Ni particles showed a water contact angle higher than 160°, corresponding to the superhydrophobicity. These superhydrophobic films were found to be resistant toward acidic and basic media. The PDMS-covered Ni particles showed high affinity toward non-polar organic solvent such as toluene. Together with an external magnetic field, the PDMS-covered Ni can be used for separating water and toluene from a water/toluene heterogeneous mixture.

Influence of Solvent Nature on the Solubility of Halogenated Alkanes

The solubility of 19 halogenated alkanes was measured in polar and nonpolar organic solvents using a dynamic method that produces more precise measurements than static methods. The solutions were analyzed with gas chromatography. A discrete-continuum solvation model was applied to investigate the influence of the solvent nature on the solubility of the compounds studied. It was shown that universal interactions between the solvent and the solute molecules, including the dispersive, inductive, and dipole–dipole interactions, dominate the solvation process. The dependences ln x298 ∼ φα and ln x298 ∼ φμ were obtained between the solubility logarithms at 298 K (ln x298) and the parameters that determine the solute–solvent interactions for nonpolar (φα) and polar (φμ) solvents, respectively. The role of the cavity formation energy in the solvation process was demonstrated. Finally, the correlation ln x298 = f(V2) was suggested, where V2 is the volume of a solute molecule in the solution.

Fabrication of fluorescence-based biosensors from functionalized CdSe and CdTe quantum dots for pesticide detection

This paper presents the results on the fabrication of highly sensitive fluorescence biosensors for pesticide detection. The biosensors are actually constructed from the complex of quantum dots (QDs), acetylcholinesterase (AChE) and acetylthiocholine (ATCh). The biosensor activity is based on the change of luminescence from CdSe and CdTe QDs with pH, while the pH is changed with the hydrolysis rate of ATCh catalyzed by the enzyme AChE, whose activity is specifically inhibited by pesticides. Two kinds of QDs were used to fabricate our biosensors: (i) CdSe QDs synthesized in high-boiling non-polar organic solvent and then functionalized by shelling with two monolayers (2-ML) of ZnSe and eight monolayers (8-ML) of ZnS and finally capped with 3-mercaptopropionic acid (MPA) to become water soluble; and (ii) CdTe QDs synthesized in aqueous phase then shelled with CdS. For normal checks the fabricated biosensors could detect parathion methyl (PM) pesticide at very low contents of ppm with the threshold as low as 0.05 ppm. The dynamic range from 0.05 ppm to 1 ppm for the pesticide detection could be expandable by increasing the AChE amount in the biosensor.