Mixtures Of Polar Solvents Research Articles

Structure and rheology of carboxymethylcellulose in polar solvent mixtures

We study the conformational, conductometric and rheological properties of semiflexible polyelectrolyte carboxymethyl cellulose in mixtures of water and three non-solvents (ethanol, isopropanol and acetone). Small angle x-ray scattering measurements of the correlation length reveal that the local conformation of the carboxymethyl chain is unchanged by the presence of a non-solvent, even for solutions not far from the solubility boundary. Rheological measurements confirm the invariance of the correlation length upon non-solvent addition. Conductivity measurements show that as the non-solvent content is increased, the fraction of condensed counterions increases, presumably due to the lowering of the dielectric constant of the solvent media. These results therefore show that under room temperature and pressure, the conformation of polyelectrolyte chains is independent of the effective charge fraction of the backbone. We suggest this occurs because the bare Kuhn length (≃10nm) is much larger than electrostatic blob size (≃1−2nm).

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study.

We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < XIL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

Excited-State Symmetry Breaking in Solvent Mixtures.

A large number of multipolar dyes undergo excited-state symmetry breaking (ESSB) in polar media. During this process, electronic excitation, initially distributed evenly over the molecule, localizes, at least partially, on one donor-acceptor branch. To resolve its initial stage, ESSB is investigated with a donor-acceptor-donor dye in binary mixtures of nonpolar and polar solvents using time-resolved infrared absorption spectroscopy. The presence of a few polar molecules around the dye is sufficient to initiate ESSB. Although the extent of asymmetry in a mixture is close to that in a pure solvent of similar polarity, the dynamics are slower and involve translational diffusion. However, preferential solvation in the mixtures leads to a larger local polarity. Furthermore, inhomogeneous broadening of the S1 ← S0 absorption band of the dye is observed in the mixtures, allowing for a photoselection of solutes with different local environments and ESSB dynamics.

A Cationic Catechol Derivative Binds Anions in Competitive Aqueous Media.

A simple dihydroxy isoquinolinium molecule (3+) was prepared by a modification of a literature procedure. Interestingly, during optimisation of the synthesis a small amount of the natural product pseudopalmatine was isolated, and characterised for the first time by X-ray crystallography. Compound 3+ contains a catechol motif and positive charge on the same scaffold and was found to be a potent anion receptor, binding sulfate strongly in 8 : 2 d6-acetone:D2O and 7 : 3 d6-acetone:D2O (Ka>104 and 2,100 M-1, respectively). Unsurprisingly, chloride binding was much weaker, even in the less polar solvent mixture 9 : 1 d6-acetone:D2O. The sulfate binding is remarkably strong for such a simple molecule, however anion binding studies were complicated by the tendency of the molecule to react with BPh4 - or BF4 - species during anion metathesis reactions. This gave two unusual zwitterions containing tetrahedral boronate centres, which were both characterised by X-ray crystallography.

Influence of H-bond competitors on the solvent-dependent structures of an octaurea-calix[4]tube.

A novel octaurea-calix[4]tube (UC4T) has been synthesized in three steps from the original Beer's p-tert-butylcalix[4]tube ionophore. In a polar solvent (DMSO-d6), UC4T rapidly interconverts between two identical conformations with C2v symmetry for the two calix[4]arene subunits. However, in a less polar solvent mixture (CDCl3/DMSO-d6, 98 : 2), UC4T adopts a highly distorted asymmetric structure, which hinders the formation of typical tetraurea calix[4]arene capsular assemblies. The complexation of potassium (or barium) cations inside the dioxyethylene ionophoric binding site of UC4T triggers a C2v to C4v symmetry rearrangement of the two calix[4]arene subunits. This rearrangement leads to the formation of a transient capsular dimeric species observed in solution upon the addition of KI or BaCl2·2H2O to a solution (CDCl3/DMSO-d6, 98 : 2) of the macrocycle. X-ray studies confirm UC4T's ability to adopt different asymmetric conformations, depending on its interactions with solvent molecules. Two distinct crystal forms (α and β) of UC4T have been obtained, each displaying divergent calix[4]arene subunits with pinched-cone conformations. These conformations exhibit distinctive head-to-tail (α) or head-to-head/tail-to-tail (β) orientations of the ureido groups, which are involved in hydrogen bonding with solvent molecules. Notably, the pseudo-capsular 1D supramolecular polymeric arrays observed in the β form of UC4T assemble to create large parallel solvent channels.

ANALYSIS OF DISSOLVING ABILITY OF LOWER ALCOHOLS AND ESTERS AQUEOUS AND HYDROCARBON SOLUTIONS TO ORGANIC MATTER OF BAZHENOV FORMATION ROCKS

This work is devoted to studying the characteristics of treatments with organic solvents on bazhenov formation rock samples, which contains a large amount of unconverted organic matter (kerogen, bitumen). This article contains the results of studying the dissolving abilities of individual low-molecular alcohols and esters, and solutions of these compounds in water and in a non-polar aromatic solvent (petroleum solvent). Among the individual solvents studied, esters of acetic acid showed the greatest dissolving ability; alcohols are less active. Petroleum solvent slightly dissolves the rock’s organic matter and needs the addition of more polar organic compounds. The dependences of dissolving ability of alcohols’ hydrocarbon solutions on alcohol concentration is extreme, with a maximum of 10 wt.%. Based on the obtained results, the mutual influence of solvents in the hydrocarbon fluid was additionally evaluated. It has been established that solutions of isopropanol and aromatic solvent show a synergistic effect to the dissolution of rock organic matter more than hydrocarbon solutions of esters. For the compositions that showed the greatest dissolving ability, a qualitative and semi-quantitative analysis was made for establishing changes in the composition of rock samples after extraction using X-Ray diffraction and Fourier-transform infrared spectroscopy. It is shown that mixtures of polar and non-polar solvents provide a more regular extraction of aliphatic and aromatic components of rock organic matter. Systems containing petroleum solvent, isopropanol and isopropyl acetate have been identified as the basis for the development of process fluids for increasing oil recovery in organic-rich reservoirs.

The isolation and characterization of lipid compounds from black soldier fly larvae

AbstractWith the global demand for lipid compounds on the rise, concerns are growing about the environmental and economic impact of traditional lipid sources. This concern is exacerbated by the ever‐increasing demand for plant‐based lipids, which is contributing to unsustainable production practices and competition for land and food. Considering this challenge, this work aimed at exploring the potential of black soldier fly larvae (BSFL) as a low‐cost and ecofriendly source of lipid classes. A fractionation scheme consisting of a mixture of polar and nonpolar solvents at different ratios was employed to isolate the lipid classes from BSFL oil using silica gel column chromatography, which is a conventional method of chromatography. The fraction's separation efficiency was validated using thin‐layer chromatography and characterized with Fourier‐transformed infrared spectroscopy and gas chromatography flame ionization (GC‐FID). Triglycerides (30%) were found to be the most abundant component while cholesterols (0.6%) were the least abundant lipid fractions in the lipid mixture. GC‐FID in the various lipid fractions analyzed, lauric acid exhibited the highest percentage among the triglycerides (16.64%), diglycerides (19.10%), monoglycerides (22.70%), and free fatty acids (27.65%) fractions. The fractionation scheme proposed achieves high efficiency in separating and recovering different lipid classes extracted from the BSFL.

Antiproliferative and pro-apoptotic effects on cancer cell line HCT116 using marine sponge Tedania species collected from Kalangahan, Lugait, Misamis Oriental, Philippines

Cancer is a major cause of mortality worldwide, and marine sponges have emerged as potential sources of anticancer agents. In this study, we investigated the antiproliferative and pro-apoptotic effects of a marine sponge extract from Tedania sp. against the human colorectal carcinoma cell line (HCT116) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Caspase-Glo® 3/7 assays. The extract was prepared using a polar solvent mixture of ethanol:water, and was subjected to reversed-phase flash chromatography consisiting of water(W), acetonitrile(ACN), and ethyl acetate(EA) gradient eluent, yielding 16 Fraction. Treatment of HCT116 cells with Fractions 1-16 showed that only Fraction 16, consisting of 100�, exhibited significant (p&lt;0.05) cytotoxic activity with the lowest viability of 90.9% compared to the negative control. Furthermore, Fraction 9, consisting of 20:80 W and ACN, showed a significantly (p&lt;0.05) highest fold change (FC) value of 2.89 indicating an almost threefold increase in caspase-3/7 activity. These results demonstrate that the Tedania sp. extract has promising antiproliferative and pro-apoptotic effects against HCT116 cell lines, indicating its potential as an anticancer agent.

Physico-chemical and biological studies of some Copper(I) complexes in binary mixtures of polar solvents at variable temperature

Physico-chemical parameters like, conductance, viscosity, volumetric, thermo acoustic, thermodynamics of viscous flow, were thoroughly evaluated from the experimentally obtained data of specific conductance, viscosity, density, and ultrasonic velocity. These parameters were evaluated for Copper(I) nitrate complexes in binary mixtures of polar solvents, Dimethylsulfoxide (DMSO), Pyridine (Py), and Nitromethane (NM) at variable temperatures (298 K-318 K) and at 1 atmospheric pressure. Ionic B values were evaluated using Jones-Dole equation to determine the extent of molecular interactions. From the measured viscosity, using Erying's transition state theory, the thermodynamic parameters of viscous flow such as Gibb's energy of activation (ΔG)*, enthalpy of activation (ΔH)*, and entropy of activation (ΔS)* were also evaluated. The thermodynamic function showed the values of ΔH* as positive for all electrolytes and ΔS* as negative. From the conductance data, the Energy of Activation (Ea) and ionic walden product (λoη) were evaluated and tabulated. Further, in order to discover more about the solute–solvent interactions, limiting apparent molar volume (ɸ˚v), Masson’s coefficient (Sv), partial molar expansibilities (ɸ˚E) and Hepler’s constant were also calculated from density and velocity data at variable temperatures. Limiting apparent molar volume ɸ˚v values for both binary mixtures were positive, indicating strong solute–solvent interactions. Thermo acoustical parameters like internal pressure (πi), Rao’s constant (Rm) and Wada’s constant (W) were also evaluated. The results from all the studies showed the possible solvation in DMSO + Py solvent mixture as compared to DMSO + NM system. Further, the copper(I) nitrate complexes with bioactive ligands were tested against Gram positive strains (S mutans MTCC 497 and S aureus MTCC 7443), Gram negative strains (S enteric MTCC 164 and P aeruginosa MTCC 4673) and fungus (A parasiticus NCIM 696, Candida albicans MTCC 183 and A niger NCIM 501). The zone of inhibition was also measured for the complexes. All the complexes with potential bioactive ligand containing Nitrogen and Sulphur atom bonded to central copper atom showed antibacterial and antifungal activity.

Comparative Study of Molecular Interaction in Ternary Liquid Mixtures of Polar and Non-Polar Solvents

Ultrasonic velocity measurements, density measurements, and viscometric studies were conducted for the ternary mixture of pyridine and toluene separately with N, N-dimethylformamide (DMF) in butanol, at different temperatures and for different concentrations of component liquids. Using these basic experimental data, various acoustic and thermodynamic parameters, such as adiabatic compressibility (β), free length (Lf,), free volume (Vf), etc. were calculated. Also, Excess thermo-acoustical parameters were calculated from the experimentally measured data. The outcomes were expressed in terms of the molecular interactions and the variations in parameters under varying solute concentrations. A comparative study is discussed. Variation in the above parameters for the different mixtures is indicative of the nature of the interactions between the components in the liquid mixture. Concluding remarks regarding intermolecular interactions are provided.

ESIPT in a binary mixture of non-polar and protic polar solvents: Role of solvation dynamics

Excited-state intramolecular proton transfer (ESIPT) was studied for two different fluorophores M2N3HF and 2P3HBQ in binary solvent mixtures of n-heptane and methanol. While both fluorophores share a degree of structural resemblance, they exhibit sharply contrasting ESIPT dynamics in the solvent mixtures. For 2P3HBQ, ESIPT is ultra-fast in n-heptane, followed by monotonic retardation in the solvent mixtures as the proportion of methanol increases, due to the predominance of 2P3HBQ⋯Methanol intermolecular H-bonding over intramolecular H-bonding within the 2P3HBQ molecule, at high methanol concentrations. For M2N3HF on the other hand, ESIPT is known to occur within sub-picosecond time-scales in alkanes and within few tens of picoseconds in methanol. However, addition of minor quantities of methanol into an alkane solvent like n-heptane causes the ESIPT to be dramatically arrested: even at 3 % mole fraction of methanol, it requires several 100 ps to complete, thus becoming ∼ 1000-fold slower than that in pure n-heptane, and ∼ 5-fold slower than that in pure methanol. Our results demonstrate that the ESIPT time-constants of M2N3HF in the solvent mixtures follow the same trend as solvation time-constants, suggesting that solvent relaxation plays a major role in the re-distribution of intra- and intermolecular H-bonds in the excited state M2N3HF. Unlike 2P3HBQ, the ESIPT of M2N3HF is thus coupled to the solvation dynamics of the solvent medium.

Anion-Responsive Fluorescent Supramolecular Gels.

Three novel bis-urea fluorescent low-molecular-weight gelators (LMWGs) based on the tetraethyl diphenylmethane spacer—namely, L1, L2, and L3, bearing indole, dansyl, and quinoline units as fluorogenic fragments, respectively, are able to form gel in different solvents. L2 and L3 gel in apolar solvents such as chlorobenzene and nitrobenzene. Gelator L1 is able to gel in the polar solvent mixture DMSO/H2O (H2O 15% v/v). This allowed the study of gel formation in the presence of anions as a third component. An interesting anion-dependent gel formation was observed with fluoride and benzoate inhibiting the gelation process and H2PO4−, thus causing a delay of 24 h in the gel formation. The interaction of L1 with the anions in solution was clarified by 1H-NMR titrations and the differences in the cooperativity of the two types of NH H-bond donor groups (one indole NH and two urea NHs) on L1 when binding BzO− or H2PO4− were taken into account to explain the inhibition of the gelation in the presence of BzO−. DFT calculations corroborate this hypothesis and, more importantly, demonstrate considering a trimeric model of the L1 gel that BzO− favours its disruption into monomers inhibiting the gel formation.

A catalytic regioselective procedure for the synthesis of aryl oximes in the presence of palladium nanoparticles

The synthesis of aryl oximes from aryl aldehyde derivatives was carried out using hydroxylamine hydrochloride and aluminum oxy hydroxide-supported palladium (Pd/AlO(OH) nanoparticles. The procedure is revealed via the regioselective synthesis of oxime derivatives in a polar solvent mixture resulting in high yields at room temperature.

Advances in Lipid Extraction Methods-A Review.

Extraction of lipids from biological tissues is a crucial step in lipid analysis. The selection of appropriate solvent is the most critical factor in the efficient extraction of lipids. A mixture of polar (to disrupt the protein-lipid complexes) and nonpolar (to dissolve the neutral lipids) solvents are precisely selected to extract lipids efficiently. In addition, the disintegration of complex and rigid cell-wall of plants, fungi, and microalgal cells by various mechanical, chemical, and enzymatic treatments facilitate the solvent penetration and extraction of lipids. This review discusses the chloroform/methanol-based classical lipid extraction methods and modern modifications of these methods in terms of using healthy and environmentally safe solvents and rapid single-step extraction. At the same time, some adaptations were made to recover the specific lipids. In addition, the high throughput lipid extraction methodologies used for liquid chromatography-mass spectrometry (LC-MS)-based plant and animal lipidomics were discussed. The advantages and disadvantages of various pretreatments and extraction methods were also illustrated. Moreover, the emerging green solvents-based lipid extraction method, including supercritical CO2 extraction (SCE), is also discussed.

Fmoc-Removal with Pyrrolidine Expands the Available Solvent Space in Green Solid-Phase Peptide Synthesis

Green binary solvent mixtures with a polarity and viscosity close to that of DMF perform similarly in solid-phase peptide synthesis (SPPS). However, while coupling reactions readily proceed in solvents of significantly lower polarity than that of DMF, a high solvent polarity is essential for Fmoc-removal using piperidine, which limits the options for green SPPS solvents. Herein, we report our efforts to expand the available solvent polarity space for green SPPS. We identified pyrrolidine as an efficient base to enable Fmoc-removal in less polar solvent mixtures that also favor coupling reactions, such as dimethyl sulfoxide/ethyl acetate (1:9) and N-butylpyrrolidone/1,3-dioxolane (2:8 and 4:6). Employing less polar binary solvent mixtures in combination with pyrrolidine gave crude peptide purities comparable to or better than for DMF with piperidine in the SPPS of challenging peptide targets. An evaluation of base-dependent side reactions such as diketopiperazine (DKP) and aspartimide formation showed increased side-product formation when using pyrrolidine on DKP- and aspartimide-prone sequences. However, the scaled-up syntheses (5 and 7.5 mmol, respectively) of the peptide therapeutics dasiglucagon (29-mer) and bivalirudin (20-mer) gave good crude peptide purities and purity profiles amenable to SPPS optimization. Pyrrolidine therefore represents a useful alternative to piperidine for Fmoc-removal in an expanded solvent space for green SPPS.

Spectroscopic thermodynamic properties of binary liquid mixtures of non-polar and polar solvents (Tetra chloromethane, 2-chloroaniline,2-methylaniline, and 2-methoxyaniline) at various temperatures

The densities (ρ), viscosities (η) and speeds of sound(u) are reported for binary mixtures of tetrachloromethane with ortho-substituted aniline (2-chloroaniline, 2-methylaniline, and 2-methoxyaniline) over the entire composition range from 298.15 K to 318.15 K and at atmospheric pressure (0.1 MPa). The excess functions and deviation in viscosity are calculated from the densities, speeds of sound and viscosities at experimental temperatures. FT-IR properties have been carried out and analyzed to study the presence of specific interaction such as the formation of hydrogen bonding of the type (N-H·····Cl) between unlike molecules in the binary liquid mixtures. A good agreement is observed among the excess parameters and FT-IR properties.

Recovery from chilling modulates the acyl-editing of phosphatidic acid molecular species in barley roots (Hordeum vulgare L.)

In plants, lipid metabolism and remodelling are key mechanisms for survival under temperature stress. The present study attempted to compare the lipid profile in barley roots both under chilling stress treatment and in the subsequent recovery to stress. Lipids were obtained through a single-extraction method with a polar solvent mixture, followed by mass spectrometry analysis. The results indicate that lipid metabolism was significantly affected by chilling. Most of the glycerolipids analysed returned to control values during short- and long-term recovery, whereas several representative phosphatidic acid (PA) molecular species were edited during long-term recovery. Most of the PA molecular species that increased in the long-term had the same acyl chains as the phosphatidylcholine (PC) species that decreased. C34:2 and C36:4 underwent the most remarkable changes. Given that the mechanisms underlying the acyl-editing of PC in barley roots remain elusive, we also evaluated the contribution of lysophosphatidylcholine acyltransferases (HvLPCAT) and phospholipase A (HvPLA). In line with the aforementioned results, the expression of the HvLPCAT and HvPLA genes was up-regulated during recovery from chilling. The differential acyl-editing of PA during recovery, which involves the remodelling of PC, might therefore be a regulatory mechanism of cold tolerance in barley.

Rapid self-assembly of γPNA nanofibers at constant temperature.

Peptide nucleic acids (PNAs) have primarily been used to achieve therapeutic gene modulation through antisense strategies since their design in the 1990s. However, the application of PNAs as a functional nanomaterial has been more recent. We recently reported that γ-modified peptide nucleic acids (γPNAs) could be used to enable formation of complex, self-assembling nanofibers in select polar aprotic organic solvent mixtures. Here we demonstrate that distinct γPNA strands, each with a high density of γ-modifications can form complex nanostructures at constant temperatures within 30 minutes. Additionally, we demonstrate DNA-assisted isothermal growth of γPNA nanofibers, thereby overcoming a key hurdle for future scale-up of applications related to nanofiber growth and micropatterning.

UV, FTIR and DFT studies of Pyrazolines in polar protic and polar aprotic solvent mixtures

UV, FTIR and DFT studies of Pyrazolines in polar protic and polar aprotic solvent mixtures

Site-to-site peptide transport on a molecular platform using a small-molecule robotic arm.

Peptides attached to a cysteine hydrazide ‘transporter module’ are transported selectively in either direction between two chemically similar sites on a molecular platform, enabled by the discovery of new operating methods for a molecular transporter that functions through ratcheting. Substrate repositioning is achieved using a small-molecule robotic arm controlled by a protonation-mediated rotary switch and attachment/release dynamic covalent chemistry. A polar solvent mixtures were found to favour Z to E isomerization of the doubly-protonated switch, transporting cargo in one direction (arbitrarily defined as ‘forward’) in up to 85% yield, while polar solvent mixtures were unexpectedly found to favour E to Z isomerization enabling transport in the reverse (‘backward’) direction in >98% yield. Transport of the substrates proceeded in a matter of hours (compared to 6 days even for simple cargoes with the original system) without the peptides at any time dissociating from the machine nor exchanging with others in the bulk. Under the new operating conditions, key intermediates of the switch are sufficiently stabilized within the macrocycle formed between switch, arm, substrate and platform that they can be identified and structurally characterized by 1H NMR. The size of the peptide cargo has no significant effect on the rate or efficiency of transport in either direction. The new operating conditions allow detailed physical organic chemistry of the ratcheted transport mechanism to be uncovered, improve efficiency, and enable the transport of more complex cargoes than was previously possible.