Showing papers on "Tetrahydrofuran published in 2017"

Biomass-Derived Butadiene by Dehydra-Decyclization of Tetrahydrofuran

Abstract: Catalytic ring-opening dehydration of tetrahydrofuran (THF), itself a product of decarbonylation and reduction of biomass-derived furfural, yields 1,3-butadiene, an important monomer in rubbers and elastomers. It is demonstrated that dehydra-decyclization of THF with phosphorus-containing siliceous self-pillared pentasil (SPP) or MFI structure exhibits high selectivity to butadiene (85–99%) at both low (9%) and high (89%) conversion of THF. High selectivity to pentadiene and hexadiene was also obtained from 2-methyl-tetrahydrofuran and 2,5-dimethyl-tetrahydrofuran, respectively, with phosphorus-containing, all-silica zeolites.

Highly selective and sensitive detection of 4-nitrophenol and Fe3+ ion based on a luminescent layered terbium (III) coordination polymer

Abstract: A luminescent terbium(III)-based coordination polymer, [Tb(BTEC)0.5(HCOO)(H2O)2] (1) has been successfully synthesized by solvothermal reaction of Tb(NO3)3·6H2O with 1,2,4,5-tetracarboxylic acid (H4BTEC) in N,N-dimethylformamide (DMF) and H2O at 160 °C. Compound 1 possesses dimeric [Tb2(BTEC)4(HCOO)2(H2O)4] building blocks which are linked by BTEC linkers to generate a two-dimentional honeycomb layer. 1 shows intense characteristic green emission in both solid state and organic solvents including acetone, ethanol, acetonitrile, benzene, dichloromethane, methanol, tetrahydrofuran, dimethyl sulfoxide and water at ambient temperature. Strong emission of 1 could be highly and selectively quenched by 4-nitropenol (4-NP) even in the coexistence of other competing nitroaromatics such as 2,4,6-trinitrophenol, 2,6-dinitrotoluene, nitrobenzene, 4-nitrotolune, 4-bromophenol, phenol, bromobenzene, and 1,2-dimethylbenzene. In addition, 1 exhibited superior selectivity and sensitivity towards Fe3+ ion over other metal ions including Al3+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Ni2+, K+, Mg2+, Mn2+, Pd2+ and Zn2+ ions. The possible detection mechanisms have been proposed. More interestingly, the trace amounts of 4-NP and Fe3+ ions were selectively detected using visual luminescent test papers based on 1, which could further contributes a credible potential sensing application of coodination polymers for the biological and environmental concerns.

Visible-Light Mediated Oxidative C-H/N-H Cross-Coupling between Tetrahydrofuran and Azoles Using Air.

Abstract: Tetrahydrofuran is a privileged structural moiety in many important organic compounds. In this work, we have developed a simple and mild catalytic oxidative amination of tetrahydrofuran mediated by visible-light catalysis. The C(sp3)-H bond of tetrahydrofuran was activated using molecular oxygen as a benign oxidant. Besides, a variety of azoles could be tolerated, providing a green route for N-substituted azoles.

How Solvent Dynamics Controls the Schlenk Equilibrium of Grignard Reagents: A Computational Study of CH3MgCl in Tetrahydrofuran

Abstract: The Schlenk equilibrium is a complex reaction governing the presence of multiple chemical species in solution of Grignard reagents. The full characterization at the molecular level of the transformation of CH3MgCl into MgCl2 and Mg(CH3)2 in tetrahydrofuran (THF) by means of ab initio molecular dynamics simulations with enhanced-sampling metadynamics is presented. The reaction occurs via formation of dinuclear species bridged by chlorine atoms. At room temperature, the different chemical species involved in the reaction accept multiple solvation structures, with two to four THF molecules that can coordinate the Mg atoms. The energy difference between all dinuclear solvated structures is lower than 5 kcal mol–1. The solvent is shown to be a direct key player driving the Schlenk mechanism. In particular, this study illustrates how the most stable symmetrically solvated dinuclear species, (THF)CH3Mg(μ-Cl)2MgCH3(THF) and (THF)CH3Mg(μ-Cl)(μ-CH3)MgCl(THF), need to evolve to less stable asymmetrically solvated sp...

Emission Tuning of Luminescent Copper(I) Complexes by Vapor-Induced Ligand Exchange Reactions.

Abstract: We have synthesized two luminescent mononuclear Cu(I) complexes, [Cu(PPh2Tol)(THF)(4Mepy)2](BF4) (1) and [Cu(PPh2Tol)(4Mepy)3](BF4) (2) (PPh2Tol = diphenyl(o-tolyl)phosphine, 4Mepy = 4-methylpyridine, THF = tetrahydrofuran), and investigated their crystal structures, luminescence properties, and vapor-induced ligand exchange reactions in the solid state. Both coordination complexes are tetrahedral, but one of the three 4Mepy ligands of complex 2 is replaced by a THF solvent molecule in complex 1. In contrast to the very weak blue emission of the THF-bound complex 1 (wavelength of emission maximum (λem) = 457 nm, emission quantum yield (Φem) = 0.02) in the solid state at room temperature, a very bright blue-green emission was observed for 2 (λem = 484 nm, Φem = 0.63), suggesting a contribution of the THF ligand to nonradiative deactivation. Time-dependent density functional theory calculations and emission lifetime measurements suggest that the room-temperature emissions of the complexes are due to thermal...

Effect of Methoxy Substituent Position on Thermal Properties and Solvent Resistance of Lignin-Inspired Poly(dimethoxyphenyl methacrylate)s

Abstract: The macromolecular properties, including the glass transition temperature (Tg) and solvent resistance, of lignin-inspired poly(dimethoxyphenyl methacrylate)s were controlled by varying the position of the dimethoxy substituents in the constituent monomers. For the four dimethoxyphenyl methacrylate isomers investigated, with substituents at different locations on the phenyl ring (i.e., 3,5-; 2,3-; 2,4-; and 2,6-), the Tg’s of the resulting polymers spanned a wide range from less than 100 °C to greater than 200 °C. Rotational freedom and segmental interactions were responsible for the varying Tg’s. The polymers were thermally stable in air up to ∼300 °C, providing a suitable thermal processing window. The poly(dimethoxyphenol methacrylate) homopolymers also exhibited remarkably different solvent resistances to organic solvents, including tetrahydrofuran and chloroform. Furthermore, by copolymerizing various dimethoxyphenyl methacrylate isomers, the Tg and solvent resistance of the resulting macromolecules c...

Sodium Diisopropylamide: Aggregation, Solvation, and Stability

Abstract: The solution structures, stabilities, physical properties, and reactivities of sodium diisopropylamide (NaDA) in a variety of coordinating solvents are described. NaDA is stable for months as a solid or as a 1.0 M solution in N,N-dimethylethylamine (DMEA) at −20 °C. A combination of NMR spectroscopic and computational studies show that NaDA is a disolvated symmetric dimer in DMEA, N,N-dimethyl-n-butylamine, and N-methylpyrrolidine. Tetrahydrofuran (THF) readily displaces DMEA, affording a tetrasolvated cyclic dimer at all THF concentrations. Dimethoxyethane (DME) and N,N,N′,N′-tetramethylethylenediamine quantitatively displace DMEA, affording doubly chelated symmetric dimers. The trifunctional ligands N,N,N′,N″,N″-pentamethyldiethylenetriamine and diglyme bind the dimer as bidentate rather than tridentate ligands. Relative rates of solvent decompositions are reported, and rate studies for the decomposition of THF and DME are consistent with monomer-based mechanisms.

Copolymerization of Carbon Dioxide with Epoxides Catalyzed by Structurally Well-Characterized Dinickel Bis(benzotriazole iminophenolate) Complexes: Influence of Carboxylate Ligands on the Catalytic Performance.

Abstract: A series of structurally well-defined dinickel carboxylate complexes based on the RBiIBTP derivatives [RBiIBTP = bis(benzotriazole iminophenolate), where R = 3C for the propyl-bridged backbone and 5C for the 2,2-dimethyl-1,3-propyl-bridged backbone] were synthesized and developed for copolymerization of CO2 and epoxides. The one-pot reactions of nickel perchlorate with the RBiIBTP-H2 proligands and an appropriate amount of carboxylic acid derivatives (CF3COOH or 4-X-C6H4CO2H; X = H, CF3, OMe) upon the addition of triethylamine in refluxing methanol (MeOH) afforded dinuclear nickel dicarboxylate complexes, which could be formulated as either [(RBiIBTP)Ni2(O2CCF3)2] (1 and 2) or [(RBiIBTP)Ni2(O2CC6H4-4-X)2] (3–7). The dinickel monobenzoate complexes [(RBiIBTP)Ni2(O2CPh)(ClO4)(H2O)] [R = 3C (8) and 5C (9)] were prepared by using a similar synthetic route in tetrahydrofuran under reflux with a ligand precursor to metal salt to benzoic acid ratio of 1:2:1 in the presence of NEt3. Recrystallization of neutral n...

Electrochemical Ammonia Synthesis Mediated by Titanocene Dichloride in Aqueous Electrolytes under Ambient Conditions

Abstract: Under ambient conditions, the catalytic and electrocatalytic syntheses of ammonia from nitrogen and various proton sources including wet tetrahydrofuran (THF) and the protic solvents methanol and water were performed using titanocene dichloride ((η5-C5H5)2TiCl2, commonly abbreviated to CP2TiCl2) in a two-electrode cell containing 1.0 M LiCl as the electrolyte. The highest rate of ammonia synthesis, 9.5 × 10–10 mol·cm–2·sec–1·M CP2TiCl2–1, was achieved at −1 V in water, whereas the highest faradaic efficiency (0.95%) was achieved at −2 V in THF. On account of its lower Gibbs free energy, density functional theory calculations suggest that the nitrogen-reduction reaction catalyzed by CP2TiCl2 in the presence of THF, methanol, or water preferably occurs via the Cp2TiClN2 intermediate rather than Cp2TiN2N2. Future strategies to improve both the rate of ammonia synthesis and its faradaic efficiency must consider ways of maximizing nitrogen selectivity to the catalytic active sites by controlling the transfer r...

Non-Grignard and Lewis Acid-Free Sulfone Electrolytes for Rechargeable Magnesium Batteries

Abstract: A major challenge for developing rechargeable Mg-ion batteries (MIB) is the lack of suitable electrolytes. We report herein dialkyl sulfones as non-Grignard and Lewis acid-free MIB electrolytes. In particular, a dipropyl sulfone (DPSO)/tetrahydrofuran (THF) (1/1, v/v) solution with MgCl2 salt exhibits high ionic conductivity (1.1 mS cm–1 at 30 °C), Mg cycling efficiency (>90%), and anodic stability (ca. 3.0 V vs Mg). As evidenced by single crystal X-ray diffraction analysis, a novel [Mg(DPSO)6]2+ cation complex balanced by two [MgCl3(THF)]− anions is identified in the DPSO/THF solution. The DPSO/THF electrolyte also enables excellent cycle performance (>300 cycles) of a Chevrel phase Mo6S8 cathode and displays a decent compatibility with an organic cathode (3,4,9,10-perylenetetracarboxylic dianhydride, PTCDA). Along with the superior electrochemical properties of the DPSO/THF electrolyte, its innate chemical stability and eco-friendly nature make it a promising MIB electrolyte.

Double Concave Cesium Encapsulation by Two Charged Sumanenyl Bowls

Abstract: The controlled reaction of Na and Cs, two alkali metals of different ionic sizes and binding abilities, with sumanene (C21H12) affords a novel type of organometallic sandwich [Cs(C21H11−)2]−, which crystallized as a solvent-separated ion pair with a [Na(18-crown-6)(THF)2]+ cation (where THF=tetrahydrofuran). The unprecedented double concave encapsulation of a metal ion by two bowl-shaped sumanenyl anions in [Cs(C21H11−)2]− was revealed crystallographically. Evaluation of bonding and energetics of the remarkable product was accomplished computationally (B2PLYP-D/TZVP/ZORA), providing insights into its formation.

Effect of Reduction Protocol of Pd Catalysts on Product Distribution in Furfural Hydrogenation

Abstract: Single step conversion of furfural to ring hydrogenation and decarbonylation products, 2-methyltetrahydrofuran (2-MeTHF) and tetrahydrofuran (THF) in high selectivity was achieved by controlling the particle size of Pd/C catalyst. The particle size variation of Pd/C catalysts in the range of 3.8 to 22 nm could be achieved by employing different reducing agents. Of particular interest was the NaBH4 reduced catalyst (Pd−B/C), which gave the lowest crystallite size of 4.8 nm due to incorporation of B into the inner lattices of Pd−Pd. This phase was evidenced by a characteristic XRD peak of Pd−B at 2θ=38.85 O as well as a shift of (111) peak (40.07 O) of Pd towards the lower value (39.8 O). As compared to formaldehyde reduced catalyst (Pd−F/C), Pd−B/C catalyst completely suppressed the formation of furfuryl alcohol to give > 65 % selectivity to 2-MeTHF and THF. At 180 OC, almost equal distribution of side chain hydrogenation and ring opening products, 2-MF (45 %) and PeDO (37 %), respectively, was observed while, higher temperature clearly favoured ring hydrogenation and decarbonylation reactions to give 2-MeTHF and THF.

Tuning Supramolecular Structure and Functions of Peptide bola-Amphiphile by Solvent Evaporation–Dissolution

Abstract: Solvent molecules significantly affect the supramolecular self-assembly, for example, in forming solvent-bridged hydrogen bonding networks. Even small changes in solvent composition can have dramatic impact on supramolecular assembly. Herein, we demonstrate the use of trace solvents (as low as 0.04%) to tune the morphology and consequent functions of supramolecular nanostructures based on an aromatic peptide bola-amphiphile. Specifically, perylene bisimide-(di)glycine-tyrosine (PBI–[GY]2) bola-amphiphile was shown to give rise to red-emitting nanofibers when assembled in water, while exposure to trace organic solvents such as tetrahydrofuran (THF) and others via solvent-evaporation followed by aqueous assembly gave rise to white-light-emitting nanospheres. Differential hydrogen bonding between water (donor and acceptor) and THF (acceptor only) impacts supramolecular organization, which was verified using a density functional theory (DFT) simulation. The tunable consequent surface hydrophobicity was utiliz...

Photo- and Electrocatalytic Hydrogen Production Using Valence Isomers of N2S2-Type Nickel Complexes

Abstract: Three Schiff-base-type nickel(II) complexes (1a–3a) and the corresponding noninnocent-type complexes (1b–3b) were synthesized, and the equilibria between these valence isomers were observed in tetrahydrofuran (THF) at room temperature. The electronic state of the noninnocent-type nickel complex was also confirmed by isolation of the one-electron-reduced species. The catalytic ability for the photogeneration of hydrogen from water was examined about 1a–3a and 1b–3b in the presence of a photosensitizer and a sacrificial electron donor. Then, a Schiff-base-type complex with chlorine atoms (2a) and a noninnocent-type complex with methyl groups (3b) on the pendant phenyl rings being present as the minor species in THF exhibited high activity of over 400 turnover numbers. The dynamic light scattering and transmission electron microscopy measurements suggested the formation of NiSx-like aggregate species under photocatalytic conditions. The electrocatalytic activities of the nickel complexes for hydrogen product...

Toolbox of Nonmetallocene Lanthanides: Multifunctional Catalysts in Group-Transfer Polymerization.

Abstract: Herein, we present a fundamental study of isostructural 2-methoxyethylamino-bis(phenolate)-lanthanide complexes [(ONOO)RM(X)(THF)] (M = Lu, Y; R = tBu, CMe2Ph, X = CH2TMS, collidine; THF = tetrahydrofuran; TMS = trimethylsilyl) for rare-earth metal-mediated group-transfer polymerization (GTP). This analysis includes the differentiation of electron-donating and nondonating vinyl monomers and two metal centers with regard to the ionic radius (yttrium and lutetium). In addition, highly nucleophilic alkyl initiators are compared with electron-donating heteroaromatic initiators. Our examinations include the impact of these parameters on the activity, initiator efficiency, and tacticity of the obtained polymers. Density functional theory calculations and proposed catalyst structure determinations via X-ray analysis support these investigations. This facilitates the selection of the best metal and initiator combination to address efficient and stereospecific polymerization of a broad range of Michael monomers. [...

Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Alkene Isomerizations and Diene Metalations

Abstract: Sodium diisopropylamide in tetrahydrofuran is an effective base for the metalation of 1,4-dienes and isomerization of alkenes. Dienes metalate via tetrasolvated sodium amide monomers, whereas 1-pentene is isomerized by trisolvated monomers. Facile, highly Z-selective isomerizations are observed for allyl ethers under conditions that compare favorably to those of existing protocols. The selectivity is independent of the substituents on the allyl ethers; rate and computational data show that the rates, mechanisms, and roles of sodium–oxygen contacts are substituent-dependent. The competing influences of substrate coordination and solvent coordination to sodium are discussed.

An experimental and theoretical kinetic study of the reaction of OH radicals with tetrahydrofuran

Abstract: Tetrahydrofuran (C4H8O, THF) and its alkylated derivatives of the cyclic ether family are considered to be promising future biofuels. They appear as important intermediates during the low-temperature oxidation of conventional hydrocarbon fuels and of heavy biofuels such as long-chain fatty acid methyl esters. The reaction of tetrahydrofuran with OH radicals was investigated in a shock tube, over a temperature range of 800–1340 K and at pressures near 1.5 bar. Hydroxyl radicals were generated by the rapid thermal decomposition of tert-butyl hydroperoxide, and a UV laser absorption technique was used to monitor the mole fraction of OH radicals. High-level CCSD(T)/cc-pV(D,T)Z//MP2/aug-cc-pVDZ quantum chemical calculations were performed to explore the chemistry of the THF + OH reaction system. Our calculations reveal that the THF + OH (R1) reaction proceeds via either direct or indirect H-abstraction from various sites, leading to the formation of tetrahydrofuran-2-yl (THF-R2) or tetrahydrofuran-3-yl (THF-R3) radicals and water. Theoretical kinetic analysis revealed that both channels are important under conditions relevant to combustion. To our knowledge, this is the first direct experimental and theoretical kinetic study of the reaction of tetrahydrofuran with OH radicals at high temperatures. The following theoretical rate expressions (in units of cm3mol−1s−1) are recommended for combustion modeling in the temperature range 800–1350 K: k 1 ( T ) = 4.11 × 10 4 ( T K ) 2.69 exp ( 1316.8 K T ) ( THF + OH → Products ) k 2 ( T ) = 6.93 × 10 11 ( T K ) 0.41 exp ( − 106.8 K T ) ( THF + OH → THF - R 2 + H 2 O ) k 3 ( T ) = 4.12 × 10 3 ( T K ) 3.02 exp ( 456.9 K T ) ( THF + OH → THF - R 3 + H 2 O )

Quantitation of the THF Content in Fe[N(SiMe3)2]2·xTHF

Abstract: The absence of residual solvent in metal precursors can be of key importance for the successful preparation of metal complexes or materials. Herein, we describe methods for the quantitation of residual coordinated tetrahydrofuran (THF) that binds to Fe[N(SiMe3)2]2, a commonly used iron synthon, when prepared according to common literature procedures. A simple method for quantitation of the amount of residual coordinated THF using 1H NMR spectroscopy is highlighted. Finally, a detailed synthetic procedure is described for the synthesis of THF-free Fe[N(SiMe3)2]2.

Speciation of ZnMe2, ZnMeCl, and ZnCl2 in Tetrahydrofuran (THF), and Its Influence on Mechanism Calculations of Catalytic Processes

Abstract: This paper examines the speciation of ZnMe2, ZnMeCl, and ZnCl2 in tetrahydrofuran (THF) solution, and provides experimental (infrared (IR) and calorimetric experiments) and density functional theory (DFT) data to conclude that the species in THF solution are, beyond a doubt, ZnMe2(THF)2, ZnMeCl(THF)2, and ZnCl2(THF)2. Consequently, coordinated THF should be used in DFT mechanistic calculations (e.g., Negishi reactions in THF). Naked or single THF coordinated molecules are virtually nonexistent in THF solutions. A cluster-continuum model for the solvent is recommended to obtain a more-correct representation. The presence or absence of THF produces a marked effect on the thermodynamics of the Negishi catalysis and a lesser effect on the kinetics of the transmetalation.

Reduction of Furfural to Furfuryl Alcohol in Liquid Phase over a Biochar-Supported Platinum Catalyst

Abstract: In this work, the liquid phase hydrogenation of furfural has been studied using a biochar-supported platinum catalyst in a batch reactor. Reactions were performed between 170 °C and 320 °C, using 3 wt % and 5 wt % of Pt supported on a maple-based biochar under hydrogen pressure varying from 500 psi to 1500 psi for reaction times between 1 h and 6 h in various solvents. Under all reactive conditions, furfural conversion was significant, whilst under specific conditions furfuryl alcohol (FA) was obtained in most cases as the main product showing a selectivity around 80%. Other products as methylfuran (MF), furan, and trace of tetrahydrofuran (THF) were detected. Results showed that the most efficient reaction conditions involved a 3% Pt load on biochar and operations for 2 h at 210 °C and 1500 psi using toluene as solvent. When used repetitively, the catalyst showed deactivation although only a slight variation in selectivity toward FA at the optimal experimental conditions was observed.

Solvent effects in hydrodeoxygenation of furfural-acetone aldol condensation products over Pt/TiO2 catalyst

Abstract: The solvent effects on hydrodeoxygenation (HDO) of 4-(2-furyl)-3-buten-2-one (F-Ac) over Pt/TiO2 catalyst were investigated at T = 200 °C and P(H2) = 50 bar. The initial reactant is the main product of aldol condensation between furfural and acetone, which constitutes a promising route for the production of bio-based chemicals and fuels. A sequence of experiments was performed using a selection of polar solvents with different chemical natures: protic (methanol, ethanol, 1-propanol, 2-propanol, 1-pentanol) and aprotic (acetone, tetrahydrofuran (THF), n,n-dimethylformamide (DMF)). In case of protic solvents, a good correlation was found between the polarity parameters and conversion. Consequently, the highest hydrogenation rate was observed when 2-propanol was used as a solvent. In contrast, the hydrogenation activity in presence of aprotic solvents was related rather to solvent-catalyst interactions. Thus, the initial hydrogenation rate declined in order Acetone > THF > DMF, i.e. in accordance with the increase in the nucleophilic donor number and solvent desorption energy. Regarding the product distribution, a complex mixture of intermediates was obtained, owing to the successive hydrogenation (aliphatic C C, furanic C C and ketonic C O bonds), ring opening (via C O hydrogenolysis) and deoxygenation reactions. Based on the proposed reaction scheme for the conversion of F-Ac into octane, the influence of the studied solvents over the cascade catalytic conversion is discussed. A significant formation of cyclic saturated compounds such as 2-propyl-tetrahydropyran and 2-methyl-1,6-dioxaspiro[4,4]nonane took place via undesirable side reactions of cyclization and isomerization. The best catalytic performance was found when using acetone and 2-propanol as solvents, achieving significant yields of 4-(2-tetrahydrofuryl)-butan-2-ol (28.5–40.4%) and linear alcohols (6.3–10.4%). The better performance of these solvents may be associated with a lower activation energy barrier for key intermediate products, due to their moderate interaction with the reactant and the catalyst. In case of methanol and DMF, undesired reactions between the reactant and the solvent took place, leading to a lower selectivity towards the targeted hydrodeoxygenated products.

Sieving of Hydrogen-Containing Gas Mixtures with Tetrahydrofuran Hydrate

Abstract: Using the different diffusion rates of gas mixture components in hydrate crystals is a promising new method for the separation of gas mixtures. The diffusion behavior of hydrogen (H2), methane (CH4), and carbon dioxide (CO2) in tetrahydrofuran (THF) hydrate was investigated experimentally by exposing a THF hydrate layer to H2, H2 + CH4, or H2 + CO2 gas or gas mixtures and monitoring the penetration of the molecules into the hydrate by Raman spectra. The experimental results demonstrate that only H2 molecules can penetrate the entire 5 mm thick hydrate layer, while the THF hydrate is resistant to CH4 and CO2 molecules on the experimental time scale employed. The minimum partial pressure for H2 to diffuse through the THF layer is 2.9 MPa, and the diffusion coefficient of H2 in the THF hydrate layer was determined to be 6.1 × 10–12 m2/s via time-resolved Raman collection. This is the first observation of the sieving behavior of a massive hydrate layer toward different gas molecules. This work also suggests t...