THF System Research Articles

Experimental measurement of gas hydrate phase equilibria in the CO2 + TBPB + THF system in the presence and absence of NaCl aqueous solution

Experimental measurement of gas hydrate phase equilibria in the CO2 + TBPB + THF system in the presence and absence of NaCl aqueous solution

A Comparative Thermal stability Study of N-(4-Nitropheny) Maleimide and N-(2, 4-di-nitrophenyl) maleimide with Methylacrylate

Abstract: In this article two type of monomers were synthesize, having different position on benzene ring one present on 4th position and second present on 2,4 position. Monomers were prepared by Maleic anhydride reaction with 2,4 dinitro aniline and 4 nitro aniline and obtained 4-Nitropheny Maleimide and 2,4-Didinitrophenylmaleimide copolymerized with Methylacrylate. Investigated a comparative study in between and what effect will come with thermal stability of the synthesis polymers. Free radical initiator AIBN and BPO were used of the polymerization and percentage yield calculated in THF and DMF solvent system under the identical conditions. Polymerization reaction proceed at different time (12, 24, 36) hours. Prepared homopolymer and copolymer were characterized by FTIR and 1H-NMR. The thermal stability and percentage degradation of the polymer were recorded by TGA Techniques. Percentage yield were obtained with given time hours and using free radical initiator and solvent systems. Synthesis polymers and their PDI values obtained range 1.5 to 10(Mw/Mn), it indicate that polymerization proceed via radical polymerization. Shape of the polymer in given solution were determined by Kuhan Mark Equations. Homopolymer shows unperturbed condition and copolymer present in rigid rods. Reduced viscosity and Intrinsic viscosity determined by the using Ubbelhod viscometer. Number average and weight average molecular weight were determined by the Gel permeation chromatography. Different feed mole ratios and percent yield were reported.

Synthesis, Spectroscopic Characterization, Crystal Structure and Theoretical Studies on New Organic Single Crystal of 1-(3,5-Difluorophenyl)-3-(2-Nitrophenyl)Urea

A new organic compound, 1-(3,5-difluorophenyl)-3-(2-nitrophenyl)urea was synthesized from 2-nitroaniline, 3,5-difluoroaniline and triphosgene in sequential two steps with 92% yield. The product was crystallized by the slow evaporation using THF and ethyl acetate solvent system to obtain its single crystal. The pure crystals were characterized with melting point, FT-IR, 1H NMR, 13C NMR and MS. The structure of the compound was brought to light by X-ray single-crystal structure determination. Density functional theory calculations were applied by using (DFT/B3LYP) method with the 6-311G(d,p) basis set level. The potential energy surface (PES) scanning was performed to determine the stability of the molecule. Frontier molecular orbitals of the compound were calculated. AIM charge and MEP analyzes were performed.

Solid-liquid equilibrium solubility measurement, model evaluation and Hansen solubility parameter of 2,4,5-trimethoxybenzaldehyde in four aqueous binary solvent mixtures

The solid–liquid equilibrium solubility of 2,4,5-trimethoxybenzaldehyde (ANH) in four kinds of aqueous binary solvent mixtures (including water + acetone, water + acetonitrile, water + N, N-dimethylformamide and water + tetrahydrofuran) was determined with a temperature ranging from 278.15 K to 323.15 K under approximately 0.1 MPa. The solubility of ANH increases with the increase of temperature and the composition of good-solvent in all the tested binary solvent mixtures. The solubility of ANH is temperature-sensitive in the binary solvent mixture of water + THF system and solvent-sensitive in the binary solvent mixture of water + DMF. The Hansen solubility parameter for ANH and the selected solvents was employed to analyze the probabilities of miscibility between solute and solvents. Four thermodynamic models (i.e., the modified Jouyban-Acree model, the Sun model, the NRTL model, and the Wilson model) were selected to correlate the experimental data. The NRTL model fitted best among all the thermodynamic models with RAD and RMSD values are less than 0.0186 (water + acetone) and 0.000950 (water + THF), respectively. The solubility data are of guiding significance to the crystallization process of ANH.

An Effective and Inexpensive Hf/ZSM-5 Catalyst for Efficient HMF Formation from Cellulose

The production of 5-hydroxymethylfurfural (HMF) from cellulose is of great significance for the high-value utilization of biomass, although this route currently faces the challenge of low efficiency. In the present work, a series of effective (x)Hf/ZSM-5 catalysts were developed for HMF production from cellulose, and analyzed by BET, XRD, SEM, ICP, NH3-TPD, Py-FTIR techniques. Driven by the (5)Hf/ZSM-5 catalyst, HMF with a yield of up to 67.5% and 17.2% of furfural are simultaneously obtained from cellulose in the H2O(NaCl)/THF biphasic system. Moreover, after four consecutive cycles, (5)Hf/ZSM-5 catalyst still maintained part of its catalytic activity. The 67.5% HMF yield achieved herein is one of the highest yields achieved in the conversion reaction using cellulose as a substrate, and the catalytic performance of the H2O(NaCl)/THF system containing the (5)Hf/ZSM-5 catalyst is even comparable to that of the expensive ionic liquid system. This result reflects the application prospect of (5)Hf/ZSM-5 catalyst in the future industrial production process of HMF.

Corrigendum to "UV-visible and fluorescence spectroscopic assessment of meso-tetrakis-(4-halophenyl) porphyrin; H2TXPP (X=F, Cl, Br, I) in THF and THF-water system: Effect of pH and aggregation behaviour" [Spectrochim. Acta A: Mol. Biomol. Spectrosc. 240 (2020) 118570

Corrigendum to "UV-visible and fluorescence spectroscopic assessment of meso-tetrakis-(4-halophenyl) porphyrin; H2TXPP (X=F, Cl, Br, I) in THF and THF-water system: Effect of pH and aggregation behaviour" [Spectrochim. Acta A: Mol. Biomol. Spectrosc. 240 (2020) 118570

UV-visible and fluorescence spectroscopic assessment of meso‑tetrakis‑(4‑halophenyl) porphyrin; H2TXPP (X=F, Cl, Br, I) in THF and THF-water system: Effect of pH and aggregation behaviour.

The current study determines optical and fluorescence response of halogen substituted series of meso‑tetrakis‑(4‑halophenyl) porphyrin; H2TXPP (Halo =F, Cl, Br, I) dye in tetrahydrofuran; THF and THF-water system at changing pH in relationship with changing medium of allure. Effects produced by varying the pH and medium, over spectral and aggregation were discussed in detail. Results show sequential protonation and deprotonation of H2TXPP series in acidic (pH=4) and (pH =10) basic medium. Specific structural changes of monomeric absorption band were put in evidence on lowering pH, which includes broadening and splitting of soret or B band. Other changes include increasing in intensity and red-shifting of Q1 band indicating some degree of aggregation. The side-by-side aggregation and formation of J-aggregate were quite evident. The red shift of B band featured self-aggregation through head-to-tail molecular ordering which is consonant with absorption-emission data.

Catalytic conversion of glucose to 5-hydroxymethylfurfural over biomass-based activated carbon catalyst

Selective and efficient dehydration of glucose to 5-hydroxymethylfurfural (HMF) has been widely explored research problem recently, especially from the perspective of more sustainable heterogeneous catalysts. In this study, activated carbon was first produced from a lignocellulosic waste material, birch sawdust. Novel heterogeneous catalysts were then prepared from activated carbon by adding Lewis or Brønsted acid sites on the carbon surface. Prepared catalysts were used to convert glucose to HMF in biphasic water:THF system at 160 °C. The highest HMF yield and selectivity, 51% and 78%, respectively, were obtained in 8 h with a catalytic mixture containing both Lewis and Brønsted acid sites. Also, preliminary recycling experiments were performed. Based on this study, biomass-based activated carbon catalysts show promise for the conversion of glucose to HMF.

Temperature Dependence Characteristics of Biodegradable Polycaprolactone Grafted Propargyl Dehydroabietic Ester (PCL-g-DAPE)

ABSTRACTA sample of propargyl dehydroabietic ester grafted to α-azide substituted poly(ϵ-caprolactone) (PCL-g-DAPE) in THF was characterized at 24°C, 30°C, 40°C, 50°C by a combination of on-line measurement of intrinsic viscosity, refractive index and two-angle light scattering in a size exclusion chromatograph. The weight average molecular weight (w), intrinsic viscosity ([η]), hydrodynamic radius (RH), and concentration of the polymer fractions were obtained from corresponding traces of the chromatograms. The data were used to construct double logarithmic plots of w versus [η], and w versus RH, as well as Stockmayer-Fixman plots, to scale the intrinsic viscosity, hydrodynamic radii and dimensions of the PCL-g-DAPE chains to molar mass. The results indicated that PCL-g-DAPE was more rigid than the parent PCL; however, PCL-g-DAPE can be classified as a flexible-coil polymer, similar to poly(methyl acrylate). The PCL-g-DAPE stiffness was related to the chemical structure of the bulky side chains that induced preferential conformation correlations of the polymer backbones in solution. The PCL-g-DAPE –THF system behaved as a lower critical consolute solution system with highest miscibility around 30°C, judged based on the slope of double logarithmic plots of molecular weight and intrinsic viscosity. Moreover, a transition in the conformation of the PCL-g-DAPE in THF at 30°C was observed.

A stable aggregate system of silyl ether substituted quinacridone and its aggregation-state changes induced by fluoride-ions: inspiration for a dual guaranteed strategy for probe design

Based on the two aggregation-state changes of the THF system of 2, a new dual guaranteed strategy for the real-time naked-eye detection of fluoride-ions was developed.

Electrochemical Charge and Discharge of Magnesium Anode in Triglyme-Based Solution

Magnesium rechargeable batteries have paid attention for the next generation battery, because magnesium metal has a higher volumetric specific capacity and higher melting point than these of lithium metal. Electrolyte for magnesium rechargeable batteries has been developed by Aurbach and co-workers [1, 2], in which Grignard reagents (RMgX, where R is an alkyl or aryl group, and X is Cl or Br) are contained. The anodic stability (about 1.7 V vs. Mg2+ / Mg) and chemical stability of the Grignard reagents-based electrolyte is not satisfied with practical application [3]. Recently, Muldoon and co-workers have developed magnesium electrolytes contain [Mg2(μ-Cl)3-6THF] [4]. The anodic stability in this electrolyte is drastically improved. However, it is still desired to improve the anodic and chemical stability. The development of new electrolyte system for magnesium rechargeable batteries is required. In this study, we investigate magnesium deposition and dissolution in triglyme-based electrolyte having high chemical stability.Electrochemical properties of the electrolyte were investigated by cyclic voltammetry with the three-electrode cell. Platinum plate and magnesium rod were used as working electrode and counter electrode, respectively. A silver wire was used as a reference electrode. Magnesium trifuluoromethanesulfonyl-imide (Mg(TFSI)2) / triglyme was used as the electrolyte. The deposition after electrochemical measurement was characterized by XRD and SEM. XRD measurements were carried out at the beam line BL02B2 at SPring-8 (Japan). Magnesium K-edge XAFS measurements were also carried out for the triglyme-based electrolyte and the Grignard reagents at the beam line BL27SU at Spring-8 (Japan).Figure 1(a) shows cyclic voltammogram of the platinum working electrode in Mg(TFSI)2 / triglyme electrolyte. The cathodic and anodic peaks correspond to magnesium deposition and dissolution, respectively. The anodic stability in this electrolyte is higher than 3.5 V vs. Mg2+ / Mg. This value is higher than that of the potential window in Grignard reagents / THF and Mg2(μ-Cl)3-6THF system. The deposited product was characterized by XRD and SEM (Fig. 1(b)). The diffraction pattern of the product is fully indexed to the P63/mmc space group, which is similar to the space group of magnesium metal. The particles with a thickness of approximately 5 mm were deposited on a platinum-working electrode. These results validate that the Mg(TFSI)2 / triglyme system can practically be used in magnesium rechargeable batteries coupled with high-voltage cathode materials. ACKNOWLEDGMENTS This work was partially supported by Core Research for Evolutional Science and Technology (CREST) program of Japan Science and Technology Agency (JST) in Japan.

Hydrate phase equilibria of CO2 + N2 + aqueous solution of THF, TBAB or TBAF system

We report hydrate dissociation conditions of CO2 (15 and 30mol%)+N2 (85 and 70mol%) in the presence of aqueous solutions of THF, TBAB or TBAF. The concentrations of TBAB and TBAF in the aqueous solutions are 5wt% and 9wt% while THF concentration in aqueous solution is 3mol%. Two different experimental techniques including isochoric pressure search method and a DSC method are used to measure the hydrate dissociation conditions. A comparison is finally made with the literature data. It is expected that this study provides better understanding of hydrate phase equilibria associated with CO2 capture.

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: Phase diagrams and molecular dynamic simulations

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

Dynamical cage behaviour and hydrogen migration in hydrogen and hydrogen-tetrahydrofuran clathrate hydrates

Classical equilibrium molecular dynamics simulations have been performed to investigate dynamical properties of cage radial breathing modes and intra- and inter-cage hydrogen migration in both pure hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 0.05 kbar and up to 250 K. For the mixed H(2)-THF system in which there is single H(2) occupation of the small cage (labelled "1SC 1LC"), we find that no H(2) migration occurs, and this is also the case for pure H(2) hydrate with single small-cavity occupation and quadruple occupancy for large cages (dubbed "1SC 4LC"). However, for the more densely filled H(2)-THF and pure-H(2) systems, in which there is double H(2) occupation in the small cage (dubbed "2SC 1LC" and "2SC 4LC," respectively), there is an onset of inter-cage H(2) migration events from the small cages to neighbouring cavities at around 200 K, with an approximate Arrhenius temperature-dependence for the migration rate from 200 to 250 K. It was found that these "cage hopping" events are facilitated by temporary openings of pentagonal small-cage faces with the relaxation and reformation of key stabilising hydrogen bonds during and following passage. The cages remain essentially intact up to 250 K, save for transient hydrogen bond weakening and reformation during and after inter-cage hydrogen diffusion events in the 200-250 K range. The "breathing modes," or underlying frequencies governing the variation in the cavities' radii, exhibit a certain overlap with THF rattling motion in the case of large cavities, while there is some overlap of small cages' radial breathing modes with lattice acoustic modes.

Studies on the Radical Cyclization of 3‐Oxopropanenitriles and Alkenes with Cerium(IV) Ammonium Nitrate in Ether Solvents

AbstractThe radical cyclization of 3‐oxopropanenitriles 1a–1e and alkenes 2a–2g with cerium(IV) ammonium nitrate (CAN) in ether solvents was investigated (Tables 1 and 2). In the optimization study, 1,3‐dioxolane, 1,4‐dioxane, 1,2‐dimethoxyethane, Et2O, and THF were used as ether‐based solvents, and the latter was found to be the most effective solvent in radical cyclizations mediated by cerium(IV). This system (cerium(IV)/THF) was applied to cyclizations of various 3‐oxopropanenitriles and 1,3‐dicarbonyl compounds with alkenes resulting in the formation of 4,5‐dihydrofurans in high yields (Table 2 and Scheme 2). The results of the cerium(IV)/THF radical cyclization were compared with those obtained with manganese(III) acetate/AcOH; the cerium(IV)/THF system turned out to be much more efficient.

Dynamical and energetic properties of hydrogen and hydrogen–tetrahydrofuran clathrate hydrates

Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the dynamical and energetic properties in hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 30 and 200 K and 0.05 kbar, and also at intermediate temperatures, using SPC/E and TIP4P-2005 water models. The potential model is found to have a large impact on overall density, with the TIP4P-2005 systems being on average 1% more dense than their SPC/E counterparts, due to the greater guest-host interaction energy. For the lightly-filled mixed H(2)-THF system, in which there is single H(2) occupation of the small cage (1s1l), we find that the largest contribution to the interaction energy of both types of guest is the van der Waals component with the surrounding water molecules in the constituent cavities. For the more densely-filled mixed H(2)-THF system, in which there is double H(2) occupation in the small cage (2s1l), we find that there is no dominant component (i.e., van der Waals or Coulombic) in the H(2) interaction energy with the rest of the system, but for the THF molecules, the dominant contribution is again the van der Waals interaction with the surrounding cage-water molecules; again, the Coulombic component increases in importance with increasing temperature. The lightly-filled pure H(2) hydrate (1s4l) system exhibits a similar pattern vis-à-vis the H(2) interaction energy as for the lightly-filled mixed H(2)-THF system, and for the more densely-filled pure H(2) system (2s4l), there is no dominant component of interaction energy, due to the multiple occupancy of the cavities. By consideration of Kubic harmonics, there is some evidence of preferential alignment of the THF molecules, particularly at 200 K; this was found to arise at higher temperatures due to transient hydrogen bonding of the oxygen atom in THF molecules with the surrounding cage-water molecules.

ChemInform Abstract: Synthetic Studies of Dihydroagarofuran Sesquiterpene: An Improved NBS-THF-H2O System for Stereoselective Construction of Tetrahydrofuran Moiety.

An improved aqueous NBS–THF system in a range of media has proved to be effective for stereoselective construction of the bromotetrahydrofuran moiety of dihydroagarofuran sesquiterpene polyesters from the corresponding β-hydroxyalkene.

Alkaline metal ion-enhanced chemiluminescence of bicyclic dioxetanes bearing a hydroxyaryl group with an ‘ even’ substitution pattern

Bicyclic dioxetane 5 bearing a 3-hydroxynaphthalen-2-yl group and its analogs 14 and 15 decomposed to give light with efficiencies of only 0.002–0.005% in a tetrabutylammonium fluoride (TBAF)/THF system, which was as expected for dioxetanes with a so-called ‘ even’ substitution pattern. However, the chemiluminescence efficiencies ( Φ CL) markedly increased when these dioxetanes were decomposed with alkaline metal t-butoxide in THF. This enhancement of Φ CL by alkaline metal ion was most likely due to the highly ordered conformation of an aromatic ring by chelate formation of the metal ion with both an oxido anion and oxygen atom of a tetrahydrofuran ring in an intermediary dioxetane like 12. Alkaline metal ion-enhanced chemiluminescence was similarly observed for dioxetane 6 bearing a 2-hydroxyphenyl group.

Well-Ordered Nanostructure SiC Ceramic Derived from Self-Assembly of Polycarbosilane-Block-Poly(methyl methacrylate) Diblock Copolymer

The fabrication of SiC ceramic materials with an ordered nanostructure through the direct pyrolysis of a self-assembled inorganic-organic block copolymer has generally been unsuccessful even though the versatile processibility has been demonstrated with organic-organic block copolymers. Here we report the synthesis of a novel polycarbosilane-block-poly(methyl methacrylate) diblock copolymer through ring-opening living anionic polymerization in a THF and n-hexane solvent system at -48 degrees C. The resulting block copolymer exhibited phase-separation behavior on the nanoscale to form a self-assembled nanostructure that was converted to a mesoporous ceramic after heating at 800 degrees C. The characterization of diblock copolymer is simultaneously investigated by GPC, and NMR analyses. The self-assembly of diblock copolymer is characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). In particular, the preparation of high-temperature-stable nanostructured silicon carbide and mesoporous silicon carbide ceramic directed from cross-linked polycarbosilane blocks with a high ceramic yield are described, which exhibits well-oriented nanostructures with the size in a range of 4-10 nm. These exciting results have a great potential to open a new field for the generation of nanostructured non-oxide ceramic or metal-ceramic materials for a broad class of applications.

Reductive openings of benzylidene acetals. Kinetic studies of borane and alane activation by Lewis acids

The reaction kinetics for a number of reductive openings of methyl 2,3-di- O-benzyl-4,6- O-benzylidene-α- d-glucopyranoside have been investigated. Openings to give free HO-6 (using BH 3·THF–AlCl 3–THF or LiAlH 4–AlCl 3–Et 2O) follow first order kinetics, while reactions yielding free HO-4 (using BH 3·NMe 3–AlCl 3–THF or BH 3·NMe 3–BF 3·OEt 2–THF) follow higher order kinetics. The addition of water to the BH 3·NMe 3–AlCl 3–THF results in faster reactions. The BH 3·SMe 2–AlCl 3–THF system constitutes a borderline case, yielding both free HO-6 (by a first order reaction) and free HO-4 (by a higher order reaction). These results correlate well with the concept of regioselectivity by activation of borane complexes.