Aqueous Solutions Of Tetrahydrofuran Research Articles

Highly Luminescent TCNQ in Melamine.

Optical properties of molecules change drastically as a result of interactions with surrounding environments as observed in solutions, clusters, and aggregates. Here, we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Colored single crystals are synthesized by slow evaporation of aqueous tetrahydrofuran solutions of melamine and TCNQ. Single-crystal X-ray diffraction reveals the lattice structure of pure melamine, meaning that the color is of impurities. Both mass spectrometry and UV-vis spectroscopy combined with density-functional theory calculations elucidate that the impurity species are neutral TCNQ and its oxidation product, dicyano-p-toluoyl cyanide anion (DCTC-), whose concentrations in a melamine crystal can be controlled by adjusting the molar ratio between melamine and TCNQ in the precursor solution. Fluorescence excitation-emission wavelength mappings on the precursor solutions illustrate dominant emissions from DCTC- while the emission from TCNQ is quenched by the resonance energy transfer to DCTC-. On the contrary, TCNQ in crystalline melamine is a bright fluorophore whose emission wavelength centered at 450 nm with internal quantum yields as high as 19% and slow fluorescence lifetimes of about 2 ns. The method of encapsulating molecules into transparent melamine would make many other molecules fluorescent in solids.

Swift and quantitative naked-eye detection of cyanide: A dual-mode approach using an ICT-based colorimetric and ratiometric fluorescent chemodosimeter

A chemodosimeter (1) based on dicyanovinyl with a strong intramolecular charge transfer (ICT) mechanism has been devised for the selective and sensitive detection of cyanide (CN−) in a tetrahydrofuran aqueous solution. In polar solvents, chemodosimeter 1 exhibits robust ICT-induced emission; however, in the solid state, its fluorescence weakens owing to the formation of molecular aggregates prompted by intermolecular π–π interactions. The colorimetric and ratiometric fluorescent changes observed in the chemodosimeter upon exposure to CN− result from the incorporation of CN− at the β-conjugated site of the dicyanovinyl moiety of chemodosimeter 1, effectively hindering the ICT process. This alteration is supported by 1H NMR titration experiments and density functional theory calculations, which corroborate the cyanide-induced ICT on–off switching mechanism. The detection limit of chemodosimeter 1 (5.8 × 10−7 M) for CN− falls below the maximum allowable level of cyanide in drinking water (1.9 × 10−6 M), as established by the World Health Organization. Test strips utilizing chemodosimeter 1 offer a potential solution for swift and quantitative naked-eye detection of CN− in real-time scenarios. Moreover, chemodosimeter 1 was effectively employed for detecting cyanide in actual environmental water samples.

Synthesis of Bench-stable Polycyclic Organophosphorus Heterocycles via Staudinger-type Annulations of ortho-Azidophenols.

The formation of a five- or six-membered ring is known to stabilize unstable molecular structures such as hemiacetals. This idea can also be extended to stabilize other high-coordinated p-block element species. Herein, we synthesized two novel polycyclic organophosphorus heterocycles via Staudinger-type annulations. Reactions of either ortho-phosphinoarenesulfonyl fluorides 1 or ortho-phosphinobenzoic acid methyl esters 4 with ortho-azidophenols 2 gave rise to penta-coordinated P(V) heterocycles, benzo-benzo-1,2,3-thiazaphospholo-1,3,2-oxazaphosphole (B-B-TAP-OAP) 3 and benzo-benzo-1,2-azaphospholo-1,3,2-oxazaphosphol-12-one (B-B-AP-OAP) 5 in satisfactory yields. It is remarkable that heterocycles 3 and 5 are both bench-stable and exhibit considerable stability in a 10 % aqueous tetrahydrofuran solution. Preliminary computational studies disclosed that the formation of nitrogen gas is the key driving force for the annulations. In addition, the formation of a strong Si-F bond is another contributor to the annulation of 1 and 2.

Phase Equilibria of Clathrate Hydrates of Ethane in the Presence of Silica Nanoparticles and Tetrahydrofuran Aqueous Solution

Phase Equilibria of Clathrate Hydrates of Ethane in the Presence of Silica Nanoparticles and Tetrahydrofuran Aqueous Solution

A bio-based reprocessable and degradable polybenzoxazine with acetal structures

In this work, a bio-based reprocessable and degradable polybenzoxazine with acetal structures was designed and prepared. A diphenol containing acetal structures (DVEA) was reacted with stearylamine and paraformaldehyde to obtain a benzoxazine monomer (DVEA-s). The curing behavior of DVEA-s was investigated using differential scanning calorimetry and in-situ Fourier transform infrared spectroscopy, and the curing kinetics of DVEA-s were also studied. Due to the thermal exchange of acetal structures, the obtained polybenzoxazine (PDVEA-s) exhibited quick stress relaxation. Mechanically crushed PDVEA-s could be reprocessed by hot-pressing at 120 °C for 10 min. Furthermore, the degradation properties of PDVEA-s under different conditions were studied. The results showed that PDVEA-s could be completely degraded in acidic tetrahydrofuran aqueous solution at 50 °C in 4 min.

Novel Bis-pyrazoline Fluorescent Probe for Cu2+ and Fe3+ Detection and Application in Cell Imaging.

A fluorescent probe Y((1,1'-([1,1'-biphenyl]-4,4'-diylbis(3-(2-hydroxyphenyl)-4,5-dihydro-1H-pyrazole-5,1-diyl)) bis(ethan-1-one))) was designed and synthesized, which could be used to Cu2+ and Fe3+ sensors. Through the study of optical properties, the probe Y shows good selectivity and sensitivity to Cu2+ and Fe3+ in aqueous tetrahydrofuran solution [10.0mM HEPES, pH 7.4, THF-H2O = 9:1(v/v)] with has excellent anti-interference performance, and its detection limits were 0.931uΜ for Cu2+ and 0.401uΜ for Fe3+. The coordination mechanism of probe Y with Cu2+ and Fe3+ was speculated and verified at DFT level and HRNM. By Hela cytotoxicity and imaging tests, probe Y not only has good biocompatibility, but also can be used for sensing Cu2+ in cells.

Experimental measurements and thermodynamic modeling of hydrate dissociation conditions for CO2 + THF + MgCl2 + water systems

• Experimental hydrate dissociation conditions for (CO2 + THF + MgCl2 + Water) system are reported. • A thermodynamic model has been developed and its results are in acceptable agreement with the experimental data. • The addition of low-medium concentration THF to the system has a promotion effect. • The addition of MgCl2 has an inhibition effect In this study, experimental and thermodynamic modeling on hydrate dissociation conditions of CO 2 + water systems in the absence/presence of MgCl 2 + THF aqueous solutions at various concentrations were investigated. The ternary systems, including different aqueous solutions of tetrahydrofuran and magnesium chloride (0.05 mass fraction of MgCl 2 , 0.05 mass fraction of THF: solution A; 0.15 mass fraction of MgCl 2 , 0.05 mass fraction of THF: solution B; 0.05 mass fraction of MgCl 2 , 0.20 mass fraction of THF: solution C; 0.15 mass fraction of MgCl 2 , 0.20 mass fraction of THF: solution D) were conducted in the temperature range between 280.9 to 292.9 K and pressure ranges 0.92 to 3.89 MPa. An isochoric pressure–search method was applied to undertake all measurements. The results demonstrated that MgCl 2 acts as an inhibitor in all experiments, while THF acts as a promoter. Comparing mentioned data with the same system in the absence of MgCl 2 , a shift is observed toward the left in the equilibrium curve that this kind of shifting left is more observable at high pressures. In addition, a thermodynamic model was developed utilizing the Peng-Robinson equation of state with classical mixing rules and the UNIQUAC activity coefficient model to predict the equilibrium conditions of the aforementioned system. The model results implied a reasonable agreement with the experimental dissociation data with an average absolute deviation of pressure below 0.3%.

Hydrogen bonding and surface tension properties of aqueous solutions of tetrahydrofuran

Significant changes observed in the tetrahydrofuran—water mixtures of different molar ratios have been determined the extent of intermolecular association via quantitative Raman experiment. The hydrogen bonding changes with the addition of tetrahydrofuran. The changes of surface tension are analyzed with hydrogen bonding in the mixtures. The result shows that the strengthening of hydrogen bonding between tetrahydrofuran and water contributes to weak the surface tension in the solutions. The correlation between surface tension and mole fractions of tetrahydrofuran is non-linear. This study provides an experimental basis for enriching the hydrogen bonding theory of multivariate aqueous solution systems.

Mechanical properties of polycrystalline tetrahydrofuran hydrates as analogs for massive natural gas hydrates

For experiments simulating marine sediments that include massive hydrate crystals for geotechnical stability assessment and for development of hydrate recovery techniques for such natural gas hydrate deposits, mechanical properties of massive natural gas hydrate crystals must be assessed as important factors affecting geotechnical stability for submarine hydrate deposits. This report describes mechanical properties of polycrystalline tetrahydrofuran hydrates of two types as analogs for massive natural gas hydrates. All tetrahydrofuran hydrate specimens exhibited brittle failure under uniaxial compression, similarly to reported massive natural gas hydrates. The uniaxial compressive strength of transparent massive hydrate specimens solidified by cooling aqueous tetrahydrofuran solution with small subcooling was 2.8–4.3 MPa. Its elastic modulus was approximately 800–1300 MPa. The strengths of cloudy massive hydrate specimens prepared from a slurry in which fine hydrate crystals were dispersed at higher subcooling were 5.3–5.7 MPa. The specimens’ elastic moduli were approximately 400 MPa. Comparison with the reported mechanical properties of massive natural gas hydrates showed that the strengths of tetrahydrofuran hydrate specimens have good agreement with the strengths of natural ones, significantly higher similarity to natural specimens was found for transparent specimens. Regarding the elastic modulus, cloudy specimens showed higher similarity to the natural specimens. The transparent specimens showed elastic modulus values that were a maximum 4.6 times higher than the natural ones.

Recording, Storage, and Reproduction of Information on Polyvinyl Chloride Films Using Shape Memory Effects.

Partial dissolution and plasticization are used for recording, storing, and reproducing information with modified industrial screen-printing equipment and aqueous solutions of colorless organic liquids on small surface area shape memory polymer films. To justify the choice of “ink” and evaluate the effectiveness of using organic liquids as high-speed polymer solvents, the new method for recording hidden information uses the calculation of the solubility parameter, differential scanning calorimetry, and the method of one-sided swelling of films under isometric conditions. Using the example of tactile marking of shrink labels made of polyvinyl chloride, the optimal conditions for recording hidden information on a film are established in terms of the concentration of an aqueous solution of tetrahydrofuran, the contact time, and the processing temperature of the polymer using screen printing equipment.

Well-Defined Lignin Model Films from Colloidal Lignin Particles.

The transformation of a molecularly complex and irregularly shaped lignin into a nanoscale spherical architecture is anticipated to play a pivotal role in the promotion of lignin valorization. From the standpoint of using colloidal lignin particles (CLPs) as building blocks for a diverse range of applications, it has become essential to study their interactions with soluble compounds of varied origin. However, the lack of model films with well-defined surface properties similar to those of CLPs has hindered fundamental studies using surface-sensitive techniques. Here, we report well-defined and stable thin films prepared from CLPs and demonstrate their suitability for investigation of surface phenomena. Direct adsorption on substrates coated with a cationic anchoring polymer resulted in uniform distribution of CLPs as shown with atomic force microscopy (AFM). Quartz crystal microbalance with dissipation monitoring (QCM-D) experiments revealed higher adsorbed mass of cationic lignin onto the CLP-coated substrate in comparison to the film prepared from dissolved lignin, suggesting preferential adsorption via the carboxylic acid enriched surfaces of CLPs. QCM-D further enabled detection of small changes such as particle swelling or partial dissolution not detectable via bulk methods such as light scattering. The CLP thin films remained stable until pH 8 and displayed only a low degree of swelling. Increasing the pH to 10 led to some instability, but their spherical geometry remained intact until complete dissolution was observed at pH 12. Particles prepared from aqueous acetone or aqueous tetrahydrofuran solution followed similar trends regarding adsorption, pH stability, and wetting, although the particle size affected the magnitude of adsorption. Overall, our results present a practical way to prepare well-defined CLP thin films that will be useful not only for fundamental studies but also as a platform for testing stability and interactions of lignin nanoparticles with materials of technical and biomedical relevance.

A Novel Fluorescent Probe Based on Pyrazole-Pyrazoline for Fe (III) Ions Recognition.

Firstly, a novel pyrazole-pyrazoline fluorescent probe was developed and synthesized. The probe can be used to determine Fe3+ ions in a series of cations in tetrahydrofuran aqueous solution with high selectivity and high sensitivity. After the addition of iron ions, the fluorescence intensity is significantly reduced, Its structure was characterized by 1H NMR, 13C NMR and HR-ESI-MS. UV absorption spectra and Fluorescence spectroscopy were used to study the selective recognition of probe M on metal ions. The probe M can selectivity and sensitivity to distinguish the target ion from other ions through different fluorescence phenomena. In addition, the binding modes of M with Fe3+ were proved to be 1:1 stoichiometry in the complexes by Job's plot, IR results. The combination of probe M and iron ions is 1:1, and the detection limit is 3.9 × 10-10 M. The binding mode and sensing mechanism of M with Fe3+ was verified by theoretical calculations using Gaussian 09 based on B3LYP/6-31G(d) basis.

Chemical reactions of tetrahydrofuran and cyclopentane hydrate by dielectric barrier discharge irradiation

We propose clathrate hydrate as a unique chemical reaction field because of its crystalline structure and high density of guest molecules. The products from tetrahydrofuran (THF) and cyclopentane (CP) hydrates by dielectric barrier discharge (DBD) irradiation were investigated at atmospheric pressure. The products were compared to those obtained by DBD irradiation of THF aqueous solution and CP/water-phase liquid. Fewer THF dimers were formed by irradiation of THF hydrates than by the irradiation of the THF aqueous solution. By introducing methane to THF hydrate, the formation of THF dimers was increased. Meanwhile, CP dimers were formed specifically by the irradiation of CP hydrates and were almost never formed by the irradiation of the CP/water-phase liquid. The difference between THF and CP in dimer formation is due to water solubility. The generation of carboxylic acid was suppressed by the irradiation of CP hydrates more than by the irradiation of the CP/water-phase liquid.

High-performance thin-film composite polyetheramide membranes for the dehydration of tetrahydrofuran

In this study, a series of pervaporation membranes is fabricated through interfacial polymerization involving a diamine and trimesoyl chloride (TMC). Three diamines are used: 2-bis(2-aminoethoxy)ethane (BAE); 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane (BATO); and 1,8-octanediamine (ODA). They differ in chemical structures and functional groups. The functional groups between the two terminal amines in BAE and BATO comprise ether groups, whereas ODA has only alkane groups. BAE or BATO reacts with TMC producing polyetheramide; the product of ODA and TMC is polyamide. Among the diamines, BAE results in a composite membrane with the most compact active layer (hence, the least free volume). This result is attributed to the two ether groups that have strong hydrogen bonding and electrostatic interaction with the amide groups. In addition, the linear orientation of the ether group contributes no steric hindrance between BAE and TMC. The polyetheramide membrane from BAE and TMC exhibits a high permeation flux of 1399 ± 132 g m−2 h−1 and a high concentration of water in the permeate of 99% (feed = 90% aqueous tetrahydrofuran solution at 30 °C). Therefore, composite polyetheramide membranes with a suitable chemical structure, fabricated under optimum conditions, deliver high efficiency for separating water from tetrahydrofuran through pervaporation.

CO2 capture from CH4–CO2 mixture by gas–solid contact with tetrahydrofuran clathrate hydrate

This study evaluated the CO2 separation characteristics for gas–solid contact between CH4 and CO2 mixtures and stoichiometric tetrahydrofuran (THF) hydrate to elucidate system temperature and pressure effects on clathrate hydrate gas separation performance. The CO2 molecules in the system were incorporated selectively into the hydrate phase during the gas–solid contact at lower temperatures. The CO2 selectivity for gas uptake was higher at higher-pressure conditions at a constant temperature. Results suggest that greater driving force for gas uptake to stoichiometric THF hydrate crystals contributes to improved CO2 selectivity from the CH4–CO2 mixture. Effects of the driving force on CO2 separation from CH4–CO2 mixture contrasted against those of gas–liquid systems using THF aqueous solution or liquid water. The different effects are expected to derive from differences in gas uptake process between gas–solid and gas–liquid systems and differences in cages for competition for gas uptake.

Molecular interactions analysis of some aluminium salts in binary aqueous solutions of tetrahydrofuran (THF): Acoustic and Conductometric approach

In the present investigation conductance and speed of sound of aluminium sulphate, aluminium nitrate, and aluminium chloride were experimentally determined in aqueous medium as well in binary aqueous mixtures of THF. Various conductance and acoustic parameters viz; molar conductance, limiting molar conductance, partial molar adiabatic compressibility, coefficient of adiabatic compressibility were also determined using Kohlrausch's Law, Debye-Huckel theory and Masson’s equation at working temperatures and different compositions of THF. Analysis reveals that limiting molar conductivity decreases with increase in composition of THF in water indicating the decrease in the ion-solvent interactions with increase in composition THF in water. Further it was found that with increase in temperature the values increase for all the three salts which support the increase in ion-solvent interactions with increase in temperature. The values of partial molar isentropic compression were found negative and these values further increase with increase in composition of THF indicating that on increase in composition, attractive interactions develop between THF and water which induces dehydration of aluminium salts which make the water molecules of aluminium salts more compressible than that of lower THF concentration resulting in decrease of ion solvent interactions with increase in THF composition in water. On the other hand with increase in temperature, the values of further increase leading to increase in ion-solvent interactions of aluminium salts in water and 5% THF+ water. Walden product and its temperature coefficient i.e. have also been calculated which confirms that aluminium salts act as structure breaker in different compositions of THF in water.

Terminal modulation of asymmetrical D−A−D−π furan-containing diketopyrrolopyrrole chromophores for intramolecular charge transfer properties

Three furan-based diketopyrrolopyrrole (DPP) chromophores have the same D−A−D structure and various tetraphenylethylene, pyrene and dibenzothiophene tails with intramolecular donor-acceptor spacers. Different π-extended chromophores show different intramolecular charge transfer properties. Furthermore, according to UV–Vis and emission spectral studies, dyes F1–F3 exhibit aggregation-caused quenching (ACQ) in tetrahydrofuran aqueous solutions. Interestingly, dyes F1 and F3 show aggregation-induced emission (AIE) behaviors in DMSO/toluene mixtures, while pyrene-functionalized DPP dye F2 still has ACQ character. It is noted that a contour plot is firstly carried out to be better understood the AIE and ACQ phenomena. Moreover, the energy gaps for the methyl counterpart of dyes F1–F3 are 2.30, 2.29 and 2.35 eV, respectively, which indicate that introducing asymmetrical D−A−D−π furan-containing DPP structures can reduce the HOMO–LUMO gaps easily and rapidly. In addition, a computational and experimental investigation has been provided, including theoretical and optical energy gaps for full comparison.

Experimental studies on hydrogen hydrate with tetrahydrofuran by differential scanning calorimeter and in-situ Raman

Clathrate hydrate is a kind of environment-friendly material for storing hydrogen under a certain condition of temperature and pressure. In this work, tetrahydrofuran aqueous solution with concentration of 3.0 mol% was adopted to investigate hydrogen storage process. Moreover, thermal property of hydrate was measured by high pressure differential scanning calorimeter, and mechanism of hydrate-based hydrogen storage was studied by in-situ Raman. Especially, gas uptake, morphology and structures change of compounds from gas/liquid interface towards hydrate layer were monitored in the process of hydrate formation. Thermal experiments illustrate that thermal data for tetrahydrofuran-hydrogen binary hydrate under extra high pressures could be effectively obtained by high pressure differential scanning calorimeter, moreover, memory effect shows no influence on thermal state of hydrate but weakly affects water aggregation. Kinetics and microscopic experiments illustrate that a special pressure drop and some tetrahydrofuran hydrates with unstable structure can be found under conditions of 273.15 K and 14.53 MPa. The pressure drop involves into hydrogen molecules tunneling movement among hydrate cavities. Moreover, hydrogen molecules show a positive effect on binary hydrate stability. Further, the density of 1.875 g/Lwater shows that hydrogen storage process via clathrate hydrate is an excellent method to store hydrogen.

Lignin as an effective agent for increasing the separation performance of crosslinked polybenzoxazine based membranes in pervaporation dehydration application

This work reports the utilization of lignin, a renewable and biomass-based material, as an effective modifying agent for thermally stable and hydrophobic membranes based on crosslinked polybenzoxazine (CRPBz) to significantly enhance their permeation fluxes in pervaporation dehydration tests. Lignin could involve in the crosslinking reaction of polybenzoxazine so as to be chemically embedded in the polymer networks. In addition to the inherent hydrophilicity of lignin, lignin could release the hydrophilic groups (phenol and tertiary amine) of crosslinked polybenzoxazine with formation of hydrogen bonding with crosslinked polybenzoxazine, consequently to significantly enhance the hydrophilicity and water permeation fluxes of the studied membranes. With feeding a 70 wt% tetrahydrofuran aqueous solution at 25 °C, lignin modification increases the permeation flux of the CRPBz based membrane from 237 g m−2 h−1 to 490 g m−2 h−1 and separation factor from 11,920 to 19,440. Lignin modification significantly enhances the water permeation flux of the membrane without scarifying separation ability. A 3.4-folds of pervaporation separation index (PSI, the product of permeation flux and separation factor) has been demonstrated with the lignin modification. Similar performance has also been recorded on the tests on a 70 wt% isopropanol aqueous solution. The effect of lignin has been attributed to increase the membrane hydrophilicity for facilitating water permeation. The results demonstrate the wide application scopes of the lignin-modified CRPBz based membranes in pervaporation dehydration based on their high stability and hydrophilicity.

Semi-clathrate hydrate process of methane in porous media-microporous materials of 5A-type zeolites

Porous media can significantly promote the kinetics of hydrate formation by reducing the barrier of physical chemistry, where zeolites are typical microporous minerals. In this paper, the formation process and the reaction kinetics of the methane hydrate were investigated in A-type zeolite with tetrahydrofuran (THF) and tetra-n-butyl ammonium bromide (TBAB) aqueous solution in a long tubular reactor. The results showed that good kinetic characteristics of methane hydrate formation can be achieved with A-type zeolite. At initial pressure of 1.5 MPa and 1.8 MPa at 285.15 K, the aqueous solution of tetrahydrofuran (THF) and tetra-n-butyl ammonium bromide (TBAB) with 5A-type zeolite can form methane hydrate with gaseous methane in 10 h. The temperature raised significantly during the formation process of the system with 5A-type zeolite. Throughout the reaction, there was an obvious temperature rising region which was located in the inlet side of tubular reactor. The gas uptake increased rapidly in the beginning of 100 min and then maintained stable increasing during the hydrate formation. The final gas uptake capacity raised with the reaction pressure but was little affected by the type of promoter. From 1.5 MPa to 1.8 MPa the final gas uptake of hydrate increased 6.48% and 6.15% in the THF and TBAB solution respectively. The reaction rate quickly reached the peak after the reaction began and then rapidly dropped to decays. Simultaneously the average of reaction rate of THF solution was 13.2–30.8% higher than that of TBAB solution when the pressure was 1.5 MPa and 1.8 MPa at the same experimental conditions.