Showing papers on "Tetrahydrofuran published in 1976"

Partial molal expansibilities of organic compounds in aqueous solution. I. Alcohols and ethers

Abstract: The temperature dependence of limiting apparent molal volumes Φ°υ in water for some alcohols (methanol, ethanol, 1-propanol, 2-butanol, 3-pentanol, 3-hexanol, 2,5-hexanediol, cyclopentanol, cyclohexanol, cycloheptanol, and 1,4-cyclohexanediol) and ethers (trimethylene oxide, tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxepane, 1,3,5-trioxane, dimethoxymethane, 1,2-dimethoxyethane, diethoxymethane, and diethyl ether) has been studied in the temperature range 10–50°C by means of an automatic digital-readout dilatometer. Values of the thermal expansion coefficient α* = (1/Φ°υ)(∂Φ°υ/∂T)p have been obtained at several temperatures and discussed together with literature data on expansibilities of related compounds. The data show a wide spectrum of values of α* at low temperatures which is narrowed at the higher ones. The expansibilities of monofunctional alcohols increase with increasing temperature; the opposite effect is observed for polyhydric alcohols. The α*'s of ethers are very slightly temperature dependent and are much higher, at low temperature, than those of alcohols having the same ratio ofno/nc. These results are discussed in terms of solutewater interactions, and a possible interpretation is put forward.

Reclamation processing of vinyl chloride polymer containing materials and products produced thereby

Abstract: Recompoundable polyvinyl chloride suitable to be recompounded for reuse, for example, in cable and wire production is recovered from a scrap material which includes plasticized polyvinyl chloride. A charge of plasticized polyvinyl chloride scrap material is treated with a solvent such as methyl ethyl ketone, tetrahydrofuran, cyclohexanone or dimethyl formamide to form a solvent mixture with one component thereof being a solvent solution of dissolved vinyl chloride polymer and plasticizers. The mixture is heated and agitated and scrap metal and other gross solids, if present, are removed. Then the solvent mixture is treated with an acid which advantageously causes a flocculation of suspended insolubles such as pigments and fillers. Except when using cyclohexanone as the solvent, the treatment with the acid must be accomplished, unexpectedly, in the presence of an additional flocculating agent such as a cellulose acetate which is soluble in the solution and which is insolubilized by the acid on refluxing. Recompoundable polyvinyl chloride is precipitated out by a non-solvent for the polyvinyl chloride which is miscible with the solvent in substantially all proportions, which will dissolve the plasticizer. The solvent and the non-solvent are removed from the plasticizer and are recovered separately by fractional distillation, for example.

Hydroboration. 44. Diisopinocampheylborane of High Optical Purity. Asymmetric Synthesis via Hydroboration with Essentially Complete Asymmetric Induction

Abstract: The reaction of borane with α-pinene in tetrahydrofuran attains equilibrium in 3 days at 0°. With 15% excess (+)-α-pinene ([α]D26.5 + 47.99°), the formation of diisopinocampheylborane is essentially quantitative (-99.5%). The longer reaction time is accompanied by a selective incorporation of the major isomer into the reagent. Thus, (+)-α-pinene, dehydroborated from diisopinocampheylborane with triethylamine, exhibits an optical rotation of [α]D23.5 + 51.0°, indicating an optical purity of 99.8%, and the isopinocampheol, obtained following the oxidation of the reagent, showed [α]D23 −35.1° (c 10, benzene), a higher rotation than any realized previously. The hydroboration of cis-2-butene with this diisopinocampheylborane in tetrahydrofuran at −25° provided 2-butanol of high optical purity, [α]D22.5 −13.29°, an optical purity of 98.4%. Thus this reaction proceeds with nearly complete asymmetric induction.

Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation

Abstract: Two samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone-water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran. Tetrahydrofuran appeared to be a more suitable solvent. The molecular weights of fractions obtained by the elution fractionation were determined by the light-scattering method in tetrahydrofuran. The width of fractions was determined by the GPC method (average Mw/Mn = 1.37); the [η] values and the Mark-Houwink constants (K = 5.3 × 10-3, a = 0.84) for tetrahydrofuran at 25°C were determined. The calibration curve for the GP method was constructed by means of the fractions thus obtained; it was demonstrated that the universal calibration curve according to Benoit can also be used. It was demonstrated that the molecular weight distribution of cellulose can be conveniently determined by conversion into CTC followed either by the elution fractionation (for preparative purposes) or by fractionation by the GPC method (for analytical purposes).

Production of tetrahydrofuran

Abstract: This invention provides a process for producing 4-hydroxybutanal in a yield of at least 87 percent by hydroformylation of allyl alcohol in a solvent at a temperature of about 20° C-120° C and a pressure of about 15-150 psi in the presence of a rhodium metal-phosphine complex hydroformylation catalyst. Also provided are additional processing procedures for recovering the 4-hydroxybutanal product and converting it into 1,4-butanediol and tetrahydrofuran.

Preparation of polymer-supported peroxy-acids and their use to oxidise olefins to epoxides

Abstract: Treatment of carboxy-substituted polystyrene resins with hydrogen peroxide in methanesulphonic acid gave resins containing aromatic peroxy-acid residues (3.5–4.0 mmol g–1). The resins generally reacted with di- and tri-substituted olefins in tetrahydrofuran at 40 °C to give epoxides (or products derived from epoxides) in yields greater than 50%. Monosubstituted olefins reacted poorly. In cases where mixtures of stereoisomeric epoxides were formed the proportions of the isomers were essentially the same as those obtained by using monomeric aromatic peroxy-acid reagents.

Kinetic and equilibrium properties of pentacyano(3,5-dimethylpyridine)-iron(II) and related anions in mixed aqueous solvents

Abstract: The kinetic pattern for reaction of [Fe(CN)5(3,5-Me2py)]3– and [Fe(CN)5,(3-CNpy)]3– with a range of incomlng groups, in water and in 40% glycol and 40% t-butyl alcohol, is consistent with the operation of a D mechanism under all the conditions studied. Rate constants for the reaction of [Fe(CN)5,(3.5-Me2py)]3– with cyanide ion have been determined in binary aqueous mixtures containing up to 40% by volume of methanol, ethanol, t-butyl alcohol, glycerol, or tetrahydrofuran. Correlation of these rate constants with Grunwald–Winstein Y values gives a value of m of –0.1; this small value reflects the low sensitivity of the rate to solvent composition. Free energies of activation determined from the observed rate constants have been plotted against excess Gibbs free energies of mixing (GE) for the respective solvent mixtures. The resulting pattern indicates how far the thermodynamic characteristics of mixing of the solvent are reflected in the kinetics of this substitution reaction. The relation between the relative stabilities of [Fe(CN)5(3,5-Me2py)]3– and its pyridine analogue, and solvent mixture GE values, has also beenexamined. Thesolvatochromic behaviourofthecharge-transfer band of [Fe(CN)5,(N-methylpyrarinium)]2– has been investigated, and contrasted with that of organic analogues.

Molecular weights of styrene–maleic anhydride copolymers†

Abstract: A dual-calibration method for the determination of molecular weights and molecular weight distribution of styrene–maleic anhydride copolymers (S/MA) by gel permeation chromatography (GPC) is introduced. It might be applicable to copolymers of other type. A linear relationship of intrinsic viscosity [η] and weight-average molecular weight (Mw) for unfractionated S/MA in tetrahydrofuran (THF) at 25°C can be expressed by the equation The maleic anhydride content of the copolymers ranges from 5 to 50 mole-%, and the Mw range is from 2 × 104 to 7 × 106. The plot of log [η] Mw versus GPC elution volume of the S/MA copolymers falls on the same curve as that of the polystyrene standards in THF.

Hydrogen bonding in the gas phase. Part 4.—Infrared spectroscopic investigation of O—H ⋯ O and C—H ⋯ N complexes : alcohol + ether and trichloromethane + amine systems

Abstract: An infrared investigation has been made of relatively weak hydrogen bonded complexes in the gas phase. Wavenumbers and band contours for hydrogen stretching modes have been investigated for O—H ⋯ O complexes formed by methanol, ethanol, propan-2-ol and 2-methylpropan-2-ol with some simple ethers, and also with tetrahydrofuran and 1,4-dioxan. The wavenumber displacements provide a measure of the electron donating abilities of the free ethers, leading to the following series according to increasing basicity : Me2O ≈ 1,4-dioxan < Et2O < THF < Pr12O. The bands for the O—H stretching vibration of the alcohol + ether systems are found to be broad but with little or no structure, and this is discussed in terms of the sum-and-difference band theory of broadening. Examples of C—H ⋯ N hydrogen bonding in the gas phase have been detected for trichloromethane + amine systems and frequency displacements are listed. The order of increasing basicity of amines as indicated by these frequency displacements is : NH3 < MeNH2 < Me2N < Me3N.

Polyurethane-urea elastomers based on propylene oxide-tetrahydrofuran copolymers

Abstract: A polyurethane-urea elastomer is prepared by reacting a copolymer of propylene oxide and tetrahydrofuran having hydroxyl end groups with an organic polyisocyanate and the isocyanate-terminated polymer is then reacted with an aromatic diamine in either bulk or solution process.

Metallboranate und Boranatometallate. IX [1]; Äther‐Addukte von Tris(boranato)‐titan(III) und dimere Alkoxy‐bis(boranato)‐titan(III)‐Verbindungen

Abstract: Inhaltsubersicht. Die Umsetzung von TiCl4 mit LiBH4 in Ather liefert fluchtiges Ti(BH4)3 · O(C2H5)2, dessen Ather durch starkere Basen (Tetrahydrofuran (THF), Dimethoxyathan, o-Dimethoxybenzol, Pyridin) verdrangt wird. Mit THF entsteht je nach Molverhaltnis ein 1:1- oder ein 1:2-Addukt. Pyridin gibt ein 1:2-Addukt und entfernt auserdem BH3-Gruppen aus Ti(BH4)3. Ti(BH4)3 · 2 THF erhalt man am besten aus Ti(OiC3H7)4 und Diboran in THF. In Ather durchgefuhrt, bleibt die Reaktion auf der Stufe von Isopropyloxybis(boranato)titan(III) stehen. Nach demselben Verfahren wurden die Athyloxy-, butyloxy- und tert.-butyloxy-Verbindungen erhalten, die sich alle als dimer erwiesen. Versuche zur Darstellung von CH3OTi(BH4)2 werden beschrieben. Die NMR-, IR- und UV-Spektren der Verbindungen werden diskutiert. Metal Tetrahydroborates and Tetrahydroboratometallates. IX. Ether Adducts of Tris-(tetrahydroborato)titanium(III) and Dimeric Alkoxy-bis(tetrahydroborato)titanium(III) Compounds Abstract. The reaction of TiCl4 with LiBH4 in ether solution yields volatile Ti(BH4)3 · O(C2H5)2, the ether of which can be displaced by stronger bases (tetrahydrofurane (THF), dimethoxyethane, o-dimethoxybenzene, pyridine). Depending on the molar ratio used 1:1- and 1:2 adducts of THF were formed. Pyridine yields a 1:2 adduct and removes BH3 groups from Ti(BH4)3. Ti(BH4)3 · 2 THF is best obtained from Ti(OiC3H7)4 and diborane in THF. This reaction carried out in ether solution, stops at the intermediate isopropyloxy-bis(tetrahydroborato)titanium(III). The same procedure yields the ethyloxy-, butyloxy- and the tert.-butyloxy compound, all of them proved to be dimeric. Experiments for preparing CH3OTi(BH4)2 are described also. The n.m.r., i.r. and u.v. spectra of the compounds are discussed.

Dehydrogenation of benzene to biphenyl by a potassium–graphite lamellar compound (KC8)

Abstract: The lamellar potassium–graphite compound KC8 forms a well defined lamellar complex with benzene and tetrahydrofuran, and because of its high affinity for hydrogen causes conversion of benzene into biphenyl.

Spectroscopic studies of ionic solvation. XXI. A raman, infrared, and NMR study of sodium perchlorate solutions in nonaqueous solvents

Abstract: Sodium perchlorate solutions in several nonaqueous solvents were examined by23Na,35Cl-NMR, infrared, and Raman spectroscopic techniques. The formation of contact ion pairs lowers the symmetry of ClO4− ion from Td to C3v or C2v provided that the interaction is fairly strong. This was manifested for NaClO4 solutions in acetonitrile, tetrahydrofuran, and pyridine. Combination of the vibrational measurements with NMR shows that in the above three cases the anion-cation interactions are quite strong. Sodium-23 NMR studies confirm the above results and, being a more sensitive technique, also indicates weak cation-anion interaction in propylene carbonate, formic acid, acetone, methanol, ethanol, dimethyl sulfoxide, and water. In all solvents the23Na resonance shifts upfield with increasing concentration of NaClO4, indicating that the replacement of solvent by ClO4− ion decreases electron density around the cation.

A new route to alkyl selenocyanate from olefin via hydroboration. reaction of organoboranes with ferric selenocyanate

Abstract: Trialkylboranes, prepared by hydroboration of terminal or internal olefins, react with ferric selenocyanate in an aqueous tetrahydrofuran to give corresponding primary or secondary alkyl selenocyanates.

Polymerization of α-Methylstyrene at High Temperatures in Tetrahydrof uran with Potassium as Initiator. I. Thermodynamic Study and Gel-Permeation Chromatographic Analyses of the Polymers

Abstract: Polymerization of α-methylstyrene in tetrahydrofuran with potassium as initiator has been studied in the -25 to 60°C temperature range. Variation of the monomer concentration at equilibrium [M]e, with its own polymer [P]e, was found to be linear at 25 and 40°C. The experiments carried out at 50, 55, and 60°C yielded high values of [P]e and polymers with high viscosity. The GPC distributions of these polymers were found to be multimodal in character, yielding four components D, A, B, and C with an average degree of polymerization, DP, of about 4, 16, 250, and 1000, respectively. It was found that the living end concentration, [LE] calculated from the viscosity-average molecular weight Mv differs to a considerable extent from those calculated on the basis of number-average molecular weight, Mn (GPC). In spite of these initial high [LE] values (10−1 and 10−2), component C had [LE] of the order of 10−3 mole/liter associated with it. The formation of high molecular weight-polymer at high temperatures ...