Showing papers on "Tetrahydrofuran published in 2007"

Viscosity, Density, Speed of Sound, and Refractive Index of Binary Mixtures of Organic Solvent + Ionic Liquid, 1-Butyl-3-methylimidazolium Hexafluorophosphate at 298.15 K

Abstract: The viscosity and refractive index of the solutions of room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6] in tetrahydrofuran, dimethylsulfoxide, methanol, and acetonitrile have been measured at 298.15 K. The density and speed of sound for solutions of [BMIM][PF6] + tetrahydrofuran or dimethylsulfoxide have also been measured. The changes in viscosity and molar refraction, the excess molar volume, and deviation in isentropic compressibility have been adequately fitted to the Redlich−Kister polynomial.

Zinc−Zinc Bonded Zincocene Structures. Synthesis and Characterization of Zn2(η5-C5Me5)2 and Zn2(η5-C5Me4Et)2

Abstract: While, in general, decamethylzincocene, Zn(C5Me5)2, and other zincocenes, Zn(C5Me4R)2 (R = H, But, SiMe3), react with dialkyl and diaryl derivatives, ZnR‘2, to give the half-sandwich compounds (η5-C5Me4R)ZnR‘, under certain conditions the reactions of Zn(C5Me5)2 with ZnEt2 or ZnPh2 produce unexpectedly the dizincocene Zn2(η5-C5Me5)2 (1) in low yields, most likely as a result of the coupling of two (η5-C5Me5)Zn• radicals. An improved, large scale (ca. 2 g) synthesis of 1 has been achieved by reduction of equimolar mixtures of Zn(C5Me5)2 and ZnCl2 with KH in tetrahydrofuran. The analogous reduction of Zn(C5Me4R)2 (R = H, SiMe3, But) yields only decomposition products, but the isotopically labeled dimetallocene 68Zn2(η5-C5Me5)2 and the related compound Zn2(η5-C5Me4Et)2 (2) have been obtained by this procedure. Compound 2 has lower thermal stability than 1, but it has been unequivocally characterized by low-temperature X-ray diffraction studies. As for 1 a combination of structural characterization techniques...

Phase relations and binary clathrate hydrate formation in the system H2-THF-H2O.

Abstract: Experimentally determined equilibrium phase relations are reported for the system H 2 -THF-H 2 O as a function of aqueous tetrahydrofuran (THF) concentration from 260 to 290 K at pressures up to 45 MPa. Data are consistent with the formation of cubic structure-II (CS-II) binary H 2 -THF clathrate hydrates with a stoichiometric THF-to-water ratio of 1:17, which can incorporate modest volumes of molecular hydrogen at elevated pressures. Direct compositional analyses of the clathrate phase, at both low (0.20 mol %) and stoichiometric (5.56 mol %) initial THF aqueous concentrations, are consistent with observed phase behavior, suggesting full occupancy of large hexakaidecahedral (5 12 6 4 ) clathrate cavities by THF, coupled with largely complete (80-90%) filling of small dodecahedral (5 12 ) cages by single H 2 molecules at pressures of >30 MPa, giving a clathrate formula of (H 2 )≤2·THF·17H 2 O. Results should help to resolve the current controversy over binary H 2 -THF hydrate hydrogen contents; data confirm recent reports that suggest a maximum of ∼1 mass % H 2 , this contradicting values of up to 4 mass % previously claimed for comparable conditions.

Amphiphilic Conjugated Block Copolymers: Synthesis and Solvent‐Selective Photoluminescence Quenching

Abstract: A novel, amphiphilic, conjugated block copolymer is described, which was prepared by a Suzuki-type cross-coupling of 2-bromo-[9,9-bis(2-ethylhexyl)fluorene]-7-pinacolato boronate as an AB-type monomer and monobromo-substituted poly[3-(6-bromohexyl)thiophene] (Br-P3BrHT) as a polymeric end capper in the key step. PF-P3PHT (P2; PF = poly(9,9-dialkylfluorene); P3PHT = poly[3-(6-diethylphosphonato-hexyl)thiophene]) as the amphiphilic target polymer was then generated in a polymer-analogous conversion of the alkyl bromide side chains of the PF-P3BrHT (P1) precursor into polar alkyl phosphonate groups by reaction with triethyl phosphite. P2 shows a strong influence of the solvent polarity on the optical spectra (absorption, emission). Treatment of solutions of P2 in tetrahydrofuran (THF), a nonselective solvent, with increasing amounts of solvents that are selective for the polar polythiophene blocks (water) or the nonpolar polyfluorene blocks (hexane), respectively, results in the formation of two different types of core-shell aggregates, which show rather different optical properties (photoluminescence quenching, excitation energy transfer).

Water-induced coacervation of alkyl carboxylic acid reverse micelles : Phenomenon description and potential for the extraction of organic compounds

Abstract: Coacervates made up of alkanoic (C8−C16) and alkenoic (C18) acid reverse micelles were described for the first time, and their potential for the extraction of organic compounds prior to liquid chromatography was examined. The coacervation process occurred in miscible binary mixtures of water and a variety of protic and aprotic solvents. The phase behavior of alkyl carboxylic acids was found to be a function of both the Hildebrand solubility parameter, δ, and the hydrogen-bonding capability of the solvent. The best solvents for analytical extractions were those featuring the lowest δ values. The phase behavior of alkyl carboxylic acid/water/tetrahydrofuran (THF) ternary systems as a function of component concentration, pH, ionic strength, and temperature was investigated. The efficiency and the time required for phase separation depended on the experimental procedure used (i.e., standing, centrifugation, stirring, and sonication). The formation of alkyl carboxylic acid reverse micelles in THF was proven us...

Catalytic Double Carbonylation of Epoxides to Succinic Anhydrides: Catalyst Discovery, Reaction Scope, and Mechanism

Abstract: The first catalytic method for the efficient conversion of epoxides to succinic anhydrides via one-pot double carbonylation is reported. This reaction occurs in two stages: first, the epoxide is carbonylated to a β-lactone, and then the β-lactone is subsequently carbonylated to a succinic anhydride. This reaction is made possible by the bimetallic catalyst [(ClTPP)Al(THF)2]+[Co(CO)4]- (1; ClTPP = meso-tetra(4-chlorophenyl)porphyrinato; THF = tetrahydrofuran), which is highly active and selective for both epoxide and lactone carbonylation, and by the identification of a solvent that facilitates both stages. The catalysis is compatible with substituted epoxides having aliphatic, aromatic, alkene, ether, ester, alcohol, nitrile, and amide functional groups. Disubstituted and enantiomerically pure anhydrides are synthesized from epoxides with excellent retention of stereochemical purity. The mechanism of epoxide double carbonylation with 1 was investigated by in situ IR spectroscopy, which reveals that the t...

Thermodynamic Stability of H2 + Tetrahydrofuran Mixed Gas Hydrate in Nonstoichiometric Aqueous Solutions

Abstract: Phase equilibria (pressure−temperature relations) of the H2 + tetrahydrofuran mixed gas hydrate system have been measured for various concentrations of tetrahydrofuran aqueous solutions. The three-phase equilibrium lines obtained in the present study are shifted to the low-temperature or high-pressure side from that of the stoichiometric THF solution. Each three-phase equilibrium line of H2 + tetrahydrofuran hydrate converges at the three-phase equilibrium line of the pure tetrahydrofuran hydrate. At the cross point on the lines, the tetrahydrofuran concentration of mother aqueous solution agrees with each other. The Raman spectra of H2 and tetrahydrofuran for the H2 + tetrahydrofuran mixed gas hydrate do not change with the variation of tetrahydrofuran mole fraction from 0.010 to 0.130 in the aqueous solution.

Bronsted basicities of diamines in the gas phase, acetonitrile, and tetrahydrofuran

Abstract: A comprehensive basicity study of alpha,omega-alkanediamines and related bases has been carried out. Basicities in acetonitrile (AN, pK(a) values), tetrahydrofuran (THF, pK(alpha) values), and gas phase (GP, GB values), were measured for 16, 14, and 9 diamine bases and for several related monoamines. In addition the gas-phase basicities and equilibrium geometries were computed for 19 diamino bases and several related monoamines at the DFT B3LYP 6-311+G** level. The effects of the different factors (intrinsic basicity of the amino groups, formation of intramolecular hydrogen bonds, and molecular strain) determining the diamine basicities were estimated by using the method of isodesmic reactions. The results are discussed in terms of molecular structure and solvation effects. The GP basicity is determined by the molecular size and polarizability, the extent of alkylation, and the energy effect of intramolecular hydrogen bond formation in the protonated base. The basicity trends in the solvents differ very much from those in GP: 1) The solvents severely compress the basicity range of the bases studied (3.5 times for the 1,3-propanediamine family in AN, and 7 times in THF), and 2) while stepwise alkylation of the basicity center leads to a steady basicity increase in the gas phase, the picture is complex in the solvents. Significant differences are also evident between THF and AN. The high hydrogen bond acceptor strength of THF leads to this solvent favoring the bases with "naked" protonation centers. In particular, the basicity order of N-methylated 1,3-propanediamines is practically inverse to that in the gas phase. The picture in AN is intermediate between that of GP and THF.

Key Interactions in Heterogeneous Ziegler−Natta Catalytic Systems: Structure and Energetics of TiCl4−Lewis Base Complexes

Abstract: Extensive calorimetric investigations on the interaction of TiCl4 with some Lewis bases are presented. Some of the bases were chosen for their industrial relevance in heterogeneous Ziegler−Natta polymerization of propene (ethyl benzoate, L2, diisobutyl phthalate, L3, (2R,3S)-diethyl 2,3-diisopropylsuccinate, L6, (2S,3S)-diethyl 2,3-diisopropylsuccinate, L7, and 9,9-bis(methoxymethyl)-9H-fluorene, L13) while other bases were chosen as probe molecules to explore the electronic and steric effects on the complexation energy (ethyl acetate, L1, diethyl phthalate, L4, diethyl succinate, L5, tetrahydrofuran, L8, dimethoxyethane, L9, dimethoxypropane, L10, dimethoxybutane, L11, and 3,3-bis(methoxymethyl)-2,6-dimethylheptane, L12). 1,1,2,2,-Tetrachloroethane was selected as the solvent for its low donating properties, which allows the focus to be on the metal−donor interaction. The calorimetric data are discussed and compared with the efficiency of the derived catalysts. Further understanding is obtained by compar...

Novel poly(pyridine imide) with pendent naphthalene groups: Synthesis and thermal, optical, electrochemical, electrochromic, and protonation characterization

Abstract: A new diamine containing a pyridine heterocyclic group and a naphthalene substituent, 4-(2-naphthyl)-2,6-bis(4-aminophenyl) pyridine (NBAPP), was synthesized with the Chichibabin reaction and used in the preparation of poly(pyridine imide) by direct polycondensation with 4,4′-hexafluoroisopropylidenediphathalic anhydride in N-methyl-2-pyrrolidinone (NMP). The poly(pyridine imide) derived from diamine NBAPP with naphthalene substituents was highly organosoluble: it was soluble in tetrahydrofuran, NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, and γ-butyrolactone at room temperature and in pyridine, dimethyl sulfoxide, and cyclohexanone upon heating at 70 °C. The poly(pyridine imide) was converted into lightly colored, optically transparent, flexible, and tough polyimide films via casting onto glass from a DMAc solution. This polymer exhibited good thermal stability (temperature of 10% weight loss = 527 °C) in air and high dielectric constants (as high as 4.20 at 1 kHz). The polyimide films had a tensile strength of 102 MPa and a tensile modulus of 1.8 GPa. As for the optical properties, the polymer exhibited UV–vis absorption bands in the region of 223–450 nm and possessed strong green-yellow fluorescence (500 nm) after being protonated with acid. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2367–2374, 2007

Ytterbium(II) complex bearing a diaminobis(phenolate) ligand: synthesis, structure, and one-electron-transfer and epsilon-caprolactone polymerization reactions.

Abstract: The first divalent ytterbium complex supported by a diaminobis(phenolate) ligand, YbL(THF)2·0.5C7H8 (1; THF = tetrahydrofuran), was synthesized in good yield by the amine elimination reaction of Yb[N(SiMe3)2]2(THF)2 with H2L (L = [Me2NCH2CH2N(CH2-2-OC6H2-3,5-But2)2]) in a 1:1 molar ratio. X-ray structural determination shows complex 1 to be a THF-solvated monomer, which adopts a distorted octahedral coordination geometry around the Yb atom. Complex 1 can react with PhNCO and PhC⋮CH, as a single electron-transfer reagent, to give the corresponding reduction coupling product [(YbLOCNPh)(THF)]2·4THF (2) and the alkynide complex YbLC⋮CPh(DME) (3; DME = 1,2-dimethoxyethane). Complexes 2 and 3 have been characterized by X-ray crystal structural analysis. In complex 2, the dianionic oxamide ligand resulting from the reductive coupling of two phenyl isocyanate molecules coordinates to two Yb atoms in a μ,η4 fashion. Complex 3 has a monomeric structure with a Yb−C(terminal phenylacetynide) bond length of 2.374(3) ...

Solvent dynamical control of ultrafast ground state electron transfer: Implications for class II-III mixed valency

Abstract: We relate the solvent and temperature dependence of the rates of intramolecular electron transfer (ET) of mixed valence complexes of the type {[Ru3O(OAc)6(CO)(L)]2−BL}-1, where L = pyridyl ligand and BL = pyrazine. Complexes were reduced chemically or electrochemically to obtain the mixed valence anions in seven solvents: acetonitrile, methylene chloride, dimethylformamide, tetrahydrofuran, dimethylsulfoxide, chloroform, and hexamethylphosphoramide. Rate constants for intramolecular ET were estimated by simulating the observed degree of ν(CO) IR band shape coalescence in the mixed valence state. Correlations between rate constants for ET and solvent properties including static dielectric constant, optical dielectric constant, the quantity 1/eop − 1/eS, microscopic solvent polarity, viscosity, cardinal rotational moments of inertia, and solvent relaxation times were examined. In the temperature study, the complexes displayed a sharp increase in the ket as the freezing points of the solvents methylene chlo...

Humidity and solvent effects in spin-coated polythiophene–polystyrene blends†

Abstract: Film blends of poly(3-butyltiophene-2,5-diyl) (PT) and polystyrene (PS; 1 : 1 w/w) were spin-coated onto silicon wafers from chloroform, tetrahydrofuran, and cyclohexanone at a controlled relative humidity between 4 and 86%. The film morphologies were determined with atomic and lateral force microscopy and mapping and depth profiling modes of dynamic secondary-ion mass spectroscopy. Independently, white light interferometry was used to examine the expansion and response time (τ) of pure polymer layers exposed to solvent vapors and moisture. The higher PS solubility, in comparison with the PT solubility, in chloroform and tetrahydrofuran resulted in PS/PT//Si bilayers, which were the final structures for coatings from chloroform [with much larger τ(PS)/τ(PT) ratios]. For tetrahydrofuran, these bilayers were destroyed, most likely by surface and interface instabilities, yielding hierarchic lateral structures. For cyclohexanone (with the largest τ values), a large-scale component of the lateral structures was absent, and this suggested the leveling of surface instabilities. The humidity changed the structural scales and thickness of the films cast from tetrahydrofuran (because it had the best solubility with water). The humidity effects of chloroform and cyclohexanone [reported earlier for polyaniline and poly(vinyl pyridine) blends] were practically absent. Moisture was not easily absorbed by PT and PS [in contrast to polyaniline and poly(vinyl pyridine)] and probably adsorbed merely at the surfaces of blend films rich in tetrahydrofuran. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci 105: 67–79, 2007

Preparation and characterization of self-assembled nanoparticles formed by poly(ethylene oxide)-block-poly(epsilon-caprolactone) copolymers with long poly(epsilon-caprolactone) blocks in aqueous solutions.

Abstract: Aqueous solutions of self-assembled nanoparticles formed by biocompatible diblock copolymers of poly(epsilon-caprolactone)-block-poly(ethylene oxide) (PCL-PEO) with the same molar mass of the PEO block (5000 g mol-1) and three different molar masses of the PCL block (5000, 13 000, and 32 000 g mol-1) have been prepared by a fast mixing the copolymer solution in a mild selective solvent, tetrahydrofuran (THF)/water, with an excess of water, that is, by quenching the reversible micellization equilibrium, and a subsequent removal of THF by dialysis of the water-rich solution against water. The prepared nanoparticles have been characterized by static and dynamic light scattering and atomic force microscopy imaging. It was found that stable monodisperse nanoparticles are formed only if the initial mixed solvent contained 90 vol % THF. The results show that the prepared nanoparticles are spherical vesicles with relatively thick hydrophobic walls, that is, spherical core/shell nanoparticles with the hollow core filled with the solvent.

New metal-organic frameworks with large cavities: selective sorption and desorption of solvent molecules.

Abstract: Five novel transition metal complexes (Cd II 3A2A6)·- A THF·3 H2 O( 1), (Cu II 3A2- A6)·6 THF·3 H2 O( 2), (Ni II 3A 2)2A6)·6 THF·3 H2 O( 3), (Cd II 2- AA3)ClO4 (4), (Cu I 3A6- A3tpba-2)) (5) (TPBA-2 = N',N'',N'''- tris(pyrid-2-ylmethyl)-1,3,5-benzenetri- carboxamide, THF = tetrahydrofuran) were obtained by reactions of the cor- responding transition metal salts with TPBA-2 ligand in the presence of NH4SCN using layering or solvother- mal method, respectively. The results of X-ray crystallographic analysis showed that complexes 1, 2 and 3 are isostructural and have the same 2D honeycomb network structure with Kagom= lattice, in which all the M II (M = Cd, Cu, Ni) atoms are six-coor- dinated, and the TPBA-2 ligands adopt cis,cis,cis conformation while the thio- cyanate anions act as terminal ligands. Capsule-like motifs are found in 1, 2 and 3, in which six THF molecules are hosted, and the results of XPRD and solid-state 13 C NMR spectral measure- ments showed that the compound 1 can selectively desorb and adsorb THF molecules occurring along with the re- establishment of its crystallinity. In contrast to 1, 2 and 3, complex 4 has different 2D network structure, result- ing from TPBA-2 ligands with cis,trans,A conformation, thiocya- nate anions serving as end-to-end bridging ligands, and the incomplete replacement of perchlorate anions, which further link the 2D layers into 3D framework by the hydrogen bonds. In complex 5, the Cu II atoms are re- duced to Cu I during the process of sol- vothermal reaction, and the Cu I atoms are connected by thiocyanate anions to form a 3D porous framework, in which the protonated TPBA-2 ligands are hosted in the cavities as templates.

N,N‘-Diisopropyl-N‘ ‘-bis(trimethylsilyl)guanidinate Ligand as a Supporting Coordination Environment in Yttrium Chemistry. Synthesis, Structure, and Properties of Complexes [(Me3Si)2NC(Ni-Pr)2]YCl2(THF)2, [(Me3Si)2NC(Ni-Pr)2]Y(CH2SiMe3)2(THF)2, and [(Me3Si)2NC(Ni-Pr)2]Y[(μ-H)(μ-Et)2BEt]2(THF)†

Abstract: The reaction of anhydrous YCl3 with an equimolar amount of lithium N,N‘-diisopropyl-N‘ ‘-bis(trimethylsilyl)guanidinate, Li[(Me3Si)2NC(Ni-Pr)2], in tetrahydrofuran (THF) afforded the monomeric monoguanidinate dichloro complex {(Me3Si)2NC(Ni-Pr)2}YCl2(THF)2 (1). Alkylation of complex 1 with 2 equiv of LiCH2SiMe3 in hexane at 0 °C yielded the monomeric salt-free dialkyl complex {(Me3Si)2NC(Ni-Pr)2}Y(CH2SiMe3)2(THF)2 (2). The bis(triethylborohydride) complex [(Me3Si)2NC(Ni-Pr)2]Y[(μ-H)(μ-Et)2BEt]2(THF) (5) was prepared by the reaction of complex 1 with 2 equiv of LiBEt3H in a toluene−THF mixture at 0 °C. The complexes 1, 2, and 5 were structurally characterized. Complex 2 as well as the systems 2−Ph3B, 2−Ph3B−MAO, and 1−MAO (MAO = methylaluminoxanes) in toluene were inactive in ethylene polymerization, while the product obtained in situ from the reaction of complex 2 with a 2-fold molar excess of PhSiH3 in toluene polymerized ethylene with moderate activity.

Investigation of the Reactions during Alkylation of Chlorine-Terminated Silicon (111) Surfaces

Abstract: Absorption infrared spectroscopy (IRAS) and Rutherford backscattering (RBS) have been used to investigate the reaction of chlorine-terminated Si(111) surfaces with organometallic molecules (Grignard reagents). Although the predominant reaction leads to alkylation, with formation of covalent Si−C bonds, evidenced by a 678 cm^(-1) feature assigned to the Si−C stretch mode, solvents typically used during alkylation (tetrahydrofuran and methanol) can also react with Cl/Si(111) surfaces, either during the alkylation reaction or during the rinsing/cleaning process to form Si−OC_nH_(2n+1) as observed by the presence of a SiO−C stretch mode at 1090 cm^(-1). We also address the origin of some silicon oxidation observed after the methylation or ethylation reactions.

Reduction of carbodiimides by samarium(II) bis(trimethylsilyl)amides-formation of oxalamidinates and amidinates through C-C coupling or C-H activation.

Abstract: The reaction of [Sm{N(SiMe3)2}2(THF)2] (THF = tetrahydrofuran) with carbodiimides RNCNR (R = Cy, C6H3-2,6-iPr2) led to the formation of dinuclear SmIII complexes via differing C−C coupling processe...