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Tetrahydrofuran

About: Tetrahydrofuran is a research topic. Over the lifetime, 11778 publications have been published within this topic receiving 158241 citations. The topic is also known as: diethylene oxide & 1,4-epoxybutane.


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Journal ArticleDOI
TL;DR: In this paper, rate studies of the N-alkylation of lithium diphenylamide with n-butyl bromide in THF/hydrocarbon mixtures (THF = tetrahydrofuran) are described.
Abstract: Rate studies of the N-alkylation of lithium diphenylamide with n-butyl bromide in THF/hydrocarbon mixtures (THF = tetrahydrofuran) are described. Dramatic induction periods observed for the N-alkylation at low THF concentrations are ascribed to the intervention of reactive mixed dimers of lithium diphenylamide and lithium bromide. In the presence of 1 .O equiv of added lithium bromide, the alkylation rate exhibits a first-order dependence on both the mixed aggregate and n-butyl bromide concentrations, supporting a pathway involving direct mixed aggregate alkylation. Incremental changes in the THF concentration uncovered contributions from several additional species. Regions of first or higher order followed by zero-order dependence on the THF concentration are interpreted as an equilibrium shift to a more reactive, highly solvated species assigned as a monomer (or ion pair). At elevated THF concentrations, the alkylation rate increases sharply as a function of the THF concentration, indicating the contribution of an additional, highly solvent dependent alkylation pathway. This latter pathway exhibits fractional-order dependence on the amide concentration, approximate first order dependence on the n-butyl bromide concentration, and a seventh-order dependence on the THF concentration. Common ion rate inhibitions by lithium perchlorate and lithium tetraphenylborate, a significant dependence on dielectric effects, and the observed reaction orders implicate a mechanism involving predissociation of free lithium ions. The appearance of competitive eliminations of the n-alkyl bromides to form 1-alkenes coincides with the appearance of the free ion alkylation pathway.

76 citations

Journal ArticleDOI
TL;DR: Aromatic polyamides based on a novel bis(ether-carboxylic acid) were synthesized by the direct phosphorylation condensation method as discussed by the authors, with high yields and moderate to high inherent viscosities (0.49-1.32 dL/g) that corresponded to weight-average and number-average molecular weights (by gel permeation chromatography) of 31,000−80,000 and 19,000-50,000, respectively.
Abstract: Aromatic polyamides based on a novel bis(ether-carboxylic acid) were synthesized by the direct phosphorylation condensation method. 1,4-Bis(4-carboxyphenoxy)-2,5-di-tert-butylbenzene was combined with various diamines containing flexible linkages and side substituents to render a set of eight novel aromatic polyamides. The polymers were produced with high yields and moderate to high inherent viscosities (0.49–1.32 dL/g) that corresponded to weight-average and number-average molecular weights (by gel permeation chromatography) of 31,000–80,000 and 19,000–50,000, respectively. Except for a single example, the polyamides were essentially amorphous and soluble in a variety of common solvents such as cyclohexanone, dioxane, and tetrahydrofuran. They showed glass-transition temperatures of 250–295 °C (by differential scanning calorimetry) and 10% weight loss temperatures above 460 °C, as revealed by thermogravimetric analysis in nitrogen. Polymer films, obtained by casting from N,N-dimethylacetamide solutions, exhibited good mechanical properties, with tensile strengths of 83–111 MPa and tensile moduli of 2.0–2.2 GPa. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 475–485, 2001

76 citations

Journal ArticleDOI
TL;DR: In this paper, an aggregation-induced emission (AIE) active linear conjugated bis-Schiff base compound, (E)-N,N′-bis(4-(Z)-2-(4-butoxyphenyl)-1-cyanovinylphenyl)-4,4-benzenebismethaneimine (4) containing αcyanostilbene unit was designed, synthesized and characterized.
Abstract: A novel aggregation-induced emission (AIE) active linear conjugated bis-Schiff base compound, (E)-N,N′-bis(4-(Z)-2-(4-butoxyphenyl)-1-cyanovinylphenyl)-1,4-benzenebismethaneimine (4) containing α-cyanostilbene unit was designed, synthesized and characterized. The distinct change of color and/or fluorescence emission of 4 + Hg2+ in tetrahydrofuran (THF) and THF/water solution provided a simple and easy discrimination way for Hg2+ by “naked eye” or using a UV lamp. The aggregating patterns of 4 were applied to explain the mechanism of sensing. The as-synthesized sample showed comparatively high selectivity and sensitivity to Hg2+ through fluorescence “turn-on” response with a low detection limit (3.4 × 10−9 M in THF, 2.4 × 10−7 M in THF/water). The results implied that the as-made sample could effectively act as Hg2+ sensor not only in THF and THF/water but in living cells.

75 citations

Journal ArticleDOI
TL;DR: Ma et al. as mentioned in this paper proposed a method to achieve the b phase of polyvinylidene fluoride (PVDF) by crystallizing from a swelling agent/solvent mixture.
Abstract: Poly(vinylidene fluoride) (PVDF) is one of the semicrystalline polymers with at least four crystalline forms referred to as a, b, c, and d phase, among which the b phase has gained substantial importance due to its advantageous pyroand piezo-electric properties [1, 2]. It requires a better method to induce the formation of b phase crystal in order to improve the electrical properties of PVDF. b phase is not usually obtained by crystallization from the melt, but it is normally obtained by various methods including tensile deformation and uniaxial compressional deformation of a phase [3, 4], blending with small contents of poly(methyl methacrylate) (PMMA) [5, 6] or poly(o-methoxyaniline) (POMA) [7], quenching and then annealing process [8], applying a strong electric field [9] and crystallizing from solution at appropriate conditions [10–12]. In all these methods which used to prepare b phase of PVDF, the one grown from a single solvent is widely used because of its facility and controllability. However, few literatures are concentrated on the solvent-induced b phase formation in the mixed solvent. In this letter a novel method to achieve the b phase of PVDF is carried out by crystallizing from swelling agent/solvent mixture. Dissolution of a semicrystalline polymer, such as PVDF, requires disruption of strong interchain forces in order regions. So the rate of polymer dissolution is dependent on the type of liquid [13]. It has been reported that tetrahydrofuran (THF) is a good swelling agent at 60 C for PVDF; N, N-dimethylformamide (DMF) is a solvent for it at 20 C [13]. The aim of this study is to include the effects of the THF/ DMF mixture with various mass ratios of each component on the crystalline phase formation and crystallization behavior in the PVDF film by solution casting. It was characterized by Fourier transform infrared (FTIR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) techniques. The PVDF (Kynar K-761, Mw = 441000) utilized in this work was supplied by Elf Atochem of North America Inc. (USA). PVDF resin was dissolved in the THF/ DMF mixture with different mass ratio (m/m composition of THF/DMF = 9:1, 8:2, and 5:5) at 50 C. The solubility of the PVDF was improved by an increase of DMF content in the mixture of solvents because of the reinforced disruption of the intermolecular polymer bonds (via interaction of the C = O dipole with the CH2CF2 dipole or by limited hydrogen bonding) [14, 15]. Films (thickness: *50 lm) of PVDF were quiescently cast from each solution with 10 wt% PVDF (initial polymer concentration) at 50 C, and the glass substrate was used for solution casting. After the solvents evaporated the films were peeled off from the glass substrate at room temperature. The residue of DMF and THF was allowed to evaporate in an air oven for about 1 week at room temperature. FTIR spectra of films were obtained on a FTIR spectrometer (Bruker Vector-22). WAXD was done in a Shimadzu XRD-6000 diffractometer (Cu Ka radiation, 40 kV and 30 mA) at a scanning velocity of 4 /min. The melting behavior of the films was measured with a Perkin– Elmer DSC-7C differential scanning calorimeter using a heating rate of 10 C/min. SEM micrographs were taken on a Jeol JSM-5900 microscope. W. Ma J. Zhang (&) College of Materials Science and Engineering, Nanjing University of Technology, No.5, Xin Mo Fan Road, Nanjing 210009, P.R. China e-mail: zhangjun@njut.edu.cn

75 citations

Journal ArticleDOI
TL;DR: Experimental results indicate that among these alkali-metal complexes, the sodium compound 6 displays a rapid catalytic polymerization of L-lactide in "living" fashion, yielding poly(L-l lactide) with a controlled molecular weight and narrow polydispersity indices for a wide range of monomer-to-initiator ratios.
Abstract: A series of lithium and sodium complexes with OOO-tridentate bis(phenolate) ligands have been synthesized and fully characterized The reaction of 2,2′-dihydroxy-3,3′,5,5′-tetrakis[(1-methyl-1-phenyl)ethyl]dibenzyl ether (L1-H2) with different ratios of nBuLi in toluene or tetrahydrofuran (THF) gave [Li2(L1-H)2] (1), [Li4L12] (2), and [Li2L1(THF)3] (3), respectively Similarly, [Na(L1-H)(THF)] (4), [Na2(L1-H)]2 (5), and [Na4L12] (6) were prepared by the reaction of L1-H2 and NaN[Si(CH3)3]2 or sodium metal In addition, the reaction of 2,2′-dihydroxy-3,3′,5,5′-tetra-tert-butyldibenzyl ether (L2-H2) with nBuLi in toluene or THF yields Li2(L2-H)2] (7) and [Li2(L2-H)2(THF)2] (8), respectively Further treatment of 7 with 2 mol equiv of benzyl alcohol provides [Li2(L2-H)2(BnOH)2] (9) Complexes 1−4 and 6−9 have been structurally characterized by single-crystal X-ray analysis The dinuclear nature of complexes 1 and 3 was confirmed from their molecular structure Complexes 2 and 6 illustrate tetranuclear specie

75 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023194
2022382
2021124
2020154
2019193
2018218