Showing papers on "Tetrahydrofuran published in 1968"

The Dimerization of Butadiene by Palladium Complex Catalysts

Abstract: It has been found that palladium-phosphine complexes coordinated by dienophile and tetrakis-(triphenylphosphine) palladium catalyzed the linear dimerization of butadiene. The dimerization of butadiene with bis(triphenylphosphine)(maleic anhydride)palladium in aprotic solvents, such as benzene, tetrahydrofuran, and acetone, gave octatriene-1,3,7 selectively in good yields. In such alcohols as methanol, ethanol, and isopropanol, butadiene was converted to 1-alkoxyoctadiene-2,7 and/or octatriene-1,3,7, depending on the nature of the alcohols employed. The dimerization in secondary amines, such as morpholine, piperidine, and diisopropylamine, gave butadiene dimer-amine adducts of the R2N(C8H13) type, while that in primary amines, such as aniline and n-butylamine, gave a mixture of RNH(C8H13) and RN(C8H13)2. Phenoxy- and acetoxyoctadiene were also obtained from the reactions in phenol and acetic acid respectively.

Determination of concentration of propagating species in cationic polymerization of tetrahydrofuran

Abstract: A spectroscopic method is described for the determination of the concentration of propagating species, [P*], in the polymerization of tetrahydrofuran catalyzed by a mixture of AlEt3−H2O (1:0.5) and epichlorohydrin. A phenyl ether group was introduced at the polymer chain end by the quantitative reaction of the propagating species with excess sodium phenoxide. From the amount of phenyl ether groups in the polymer and of the remaining sodium phenoxide, [P*] was determined by means of ultraviolet spectroscopy. The [P*] value so determined was found to be in good agreement with that calculated from the amount and molecular weight of polymer based on a stepwise addition mechanism without chain transfer or termination. The present method of [P*] determination was employed to examine the course of polymerization. It has now been found that [P*] increases progressively during an induction period and remains unchanged in the subsequent period of polymerization.

A variable-temperature nuclear magnetic resonance study of complexes of borane and boron trihalides with acetone, diethyl ether, dimethyl ether, n,n-dimethylformamide, methanol, and tetrahydrofuran.

Abstract: : A proton and boron-11 chemical shift and coordination number study of complexes of diborane and the boron trihalides with dimethyl ether, diethyl ether, methanol, tetrahydrofuran, and, to a small extent, acetone and N,N-dimethylformamide has been completed. At low temperatures, separate proton resonance signals are observed for bulk solvent and solvent molecules complexed with the boron species. Coordination numbers were measured by the direct integration of the separate signals. The chemical shift separations for bulk and complexed solvent signals decreased in the order BBr3 > BCl3 > BF3 > BH3. An attempt is made to relate these separations to the coordinating abilities of the boron halides. The proton chemical shift data of the bases were correlated with some diborane 11B and 1H nuclear magnetic resonance results to obtain information concerning the species present in the ether-diborane solution. (Author)

Azomethine derivatives. Part V. Reactions between organolithium compounds and diphenylketimine, some cyanides, and NNN′N′-tetramethylguanidine

Abstract: Reactions in ether between methyl-lithium and diphenylketimine, or between phenyl-lithium and phenyl cyanide, give a red solution of diphenylketiminolithium, Ph2C:NLi, from which unsolvated (Ph2C:NLi)n may be obtained as a yellow amorphous and presumably polymeric solid, m. p. 260°(decomp.). Diphenylketiminolithium forms the coloured crystalline adducts Ph2C:NLi,py, m. p. 108–110°(red) and Ph2C:NLi, tetrahydrofuran, m. p. 127°(orange) which dissociate in benzene and deposit (Ph2C:NLi)n. Phenyl cyanide and methyl-lithium give yellow amorphous (PhCMe:NLi)n, m. p. 196°. t-Butyl cyanide does not react with methyl-or ethyl-lithium at or below 20°, but methyl and ethyl cyanides with these alkyl-lithium compounds cleave alkane to give amorphous insoluble highly reactive solids believed to contain CCN– groups. A similarly reactive and apparently polymeric, insoluble solid results when dimethylcyanamide and methyl-lithium react and evolve methane. NNN′N′-Tetramethylguanidine and methyl-lithium give methane and the crystalline derivative [(Me2N)2C:NLi]2 which is dimeric in benzene (by cryoscopy) and is also soluble in ether and toluene.

Synthesis, structure, and properties of π-cyclo-octenyl-π-cyclo-octa-1,5-dienecobalt

Abstract: Treatment of cobalt dichloride suspended in a mixture of cyclo-octa-1,5-diene, pyridine, and tetrahydrofuran with metal sodium affords a brown crystalline complex, Co(C8H13)(C8H12). Structural proof has been obtained which shows conclusively that the complex is π-cyclo-octenyl-π-cyclo-octa-1,5-dienecobalt. Thermally it is stable, and shows no tendency for valence tautomerism. Remarkable mobility of the hydrogen atoms of the ligand has been observed in some chemical reactions, and this is interpreted in terms of the molecular structure.

Studies of solution properties of copolymers. II. Copolymer of maleic anhydride and styrene

Abstract: Styrene and maleic anhydride were copolymerized in benzene. The whole polymer thus obtained was fractionated with acetone and petroleum ether as the solvent and precipitant, respectively. The viscosities and osmotic pressures of the fractions were determined in tetrahydrofuran. The relation between the intrinsic viscosity and the molecular weight, [η] = 5.07 × 10−5 Mn0.81, was obtained in tetrahydrofuran. The unperturbed mean square end-to-end distance was estimated by the Stockmayer-Fixman equation. A theoretical equation for the mean square end-to-end distance for a chain of repeating units of different bond lengths a and b with a fixed valence angle θ and without restriction of internal rotation was presented and applied to this copolymer. In addition, the equation of the mean-square end-to-end distance derived by Wall for trans-polyisoprene without rotational restriction was modified for application to this copolymer. The result evaluated with our equation was about 26% smaller than that from the modified Wall equation. A steric parameter for the present copolymer is defined and discussed in comparison with those of polystyrenesulfone and polystyrene.

Kinetics of Isotopic Exchange between Acetylacetone-14C and Tris-acetylacetonatoaluminum in Tetrahydrofuran

Abstract: Tris-acetylacetonatoaluminum [Al(acac)3] is precipitated crystalline from tetrahydrofuran (THF) solution containing an excess of acetylacetone (acacH) by adding chilled petroleum ether. This fact enables a kinetic study of isotopic exchange of acac− between [Al(acac)3] and acacH with the aid of acetylacetone-14C. The exchange rate is independent of the concentration of acacH and dependent on that of water. The rate formula at 25°C is as follows: R=[Al(acac)_3](6×10^-5+2.0×10^-2[H_2O]) mol l^-1min^-1 This exchange reaction is catalysed by acids; the stronger the acid, the greater the catalytic effect. One of the acetylacetonate ligands would be present with one end free, and break of the remaining bond of unidentate acetylacetonate seems to be the rate determining step. Water can occupy the vacant coordination site of aluminum ion to retard recombination of the unidentate ligand. The donation of proton to the free end of acetylacetonate appears to impede the recombination, too, and facilitate the exchange....

Heats of Mixing for Binary Mixtures. V

Abstract: The heats of mixing were measured at 25.0°C for binary mixtures of chloroform+tetrahydrofuran,+furan, and +2-methyl furan systems and for cyclohexane+chloroform,+tetrahydrofuran,+furan, and +2-methyl furan systems. Using these data and the treatment described in a previous paper [Bull. Chem. Soc. Japan, 37, 1776 (1964)], the intermodular hydrogen bond energies between chloroform and cyclic ethers were estimated to be ΔH=−12 kJ for the chloroform-tetrahydrofuran-cyclohexane system, ΔH=−4 kJ for the chloroform -2-methyl furan-cyclohexane system, and ΔH=−3 kJ for the chloroform-furan-cyclohexane system. From these results, two types of intermolecular hydrogen bonds between chloroform and cyclic ethers are discussed.

Saturated hydrocarbon prepolymer and reaction products thereof

Abstract: 1,189,494. Copolymers. UNION CARBIDE CORP. 11 May, 1967, No. 22017/67. Heading C3P. [Also in Division C5] Saturated hydrocarbon prepolymers comprise a substantially random interpolymer of ethylene and 5 to 70 weight per cent of an α-olefin or fluorine - substituted α - olefin H 2 C = CHCR 3 , where each R is C 1-6 alkyl or fluorine, said interpolymer having an average of 1 to 2 reactive functional groups attached to terminal carbon atoms of each polymer molecule and selected from hydroxy, carboxy, amino, cyano, formyl, aziridinyl and alkoxycarbonyl. Polymerization may be effected in bulk or solution, e.g. in hydrocarbons, ketones and cyclic ethers, in the presence of organic peroxides or azo compounds whereby such end groups as cyano, carboxy and alkoxycarbonyl may be introduced. These may be oxidized, reduced, hydrolysed or converted to chloride and reacted with ethylene imine to provide other desired end groups. The prepolymers may be converted to linear high polymers by reacting with difunctional compounds capable of reacting with the terminal groups, and cross-linked by reacting with compounds having a functionality greater than 2. Many suitable compounds are listed including polyepoxides, polyisocyanates, polyaziridines, polyamines, polyols and polybasic acids. The prepolymers may be used for potting compounds, polishes and inks and lithium and sodium salts thereof as lubricants, and the high polymers as potting compounds, electrical insulation, sealants, gaskets, weatherstrips, fibres, films and mouldings. In examples ethylene and neohexene are polymerized in the presence of (I-VI and X-XIV) benzene and azodiisobutyronitrile; (IX) tetrahydrofuran and succinic acid peroxide; (XVI) tetrahydrofuran and 4,4 1 -azobis-4-cyanopentanoic acid together with (XVII) dithiodibutyric acid; and (XVIII) benzene and diethyl - 2,2 1 - azobisisobutyrate; -CN terminal groups are hydrolysed to -COOH by acid or alkaline hydrolysis and terminal ethoxycarbonyl groups are reduced to -OH with lithium aluminium hydride; and ethylene/neohexene copolymers having terminal -COOH groups are reacted with (I) triglycidyl ether of p-aminophenol, 2,4-tolylene diisocyanate and succinic acid: (II) and (III) tris propylene imine phosphoric oxide; (IX) propane triol and ethylene glycol; and having terminal -OH groups are reacted with (XVIII) tris (N-methylethyleneimine) phosphorus oxide.

Some alkylmagnesium alkoxides and reaction products from Grignard reagents and carbonyl compounds

Abstract: Several alkylmagnesium alkoxides have been prepared by alcoholysis of the dialkyls in diethyl ether, and can be obtained free from ether. In benzene, EtMgOPrn, PriMgOMe, and PriMgOEt are oligomers (degrees of association ca. 8), but those alkoxides we have studied in which there is chain-branching α to oxygen are tetramers, (EtMgOPri)4, (EtMgOBut)4, and (PriMgOPri)4. The 3-ethyl-pentan-3-ol derivative, from Et2Mg + Et2COor Et2Mg + Et3COH, crystallises as an ether complex (EtMgOCEt3,Et2O) which loses ether very readily: the tetrahydrofuran adduct is dimeric in benzene (EtMgOCEt3,THF)2. Some alkylmagnesium alkoxides are tetramers in diethyl ether, (EtMgOEt)4, (MeMgOBut)4, and (EtMgOBut)4, but two are dimers, (EtMgOCMeEt2)2 and (EtMgOCEt3)2. Methylmagnesium t-butoxide disproportionates in dilute solution in benzene. Both dimethyl-magnesium and ethylmagnesium ethoxide crystallise from diethyl ether at room temperature without solvent of crystallisation.The diethyl ether complex of t-butoxymagnesium bromide crystallises from the solution obtained when acetone is added to methylmagnesium bromide in ether. It is a dimer, (ButOMgBr,EtO)2, both in benzene and in ether and in the crystalline state. Several analogous products have been obtained by other similar reactions, and all those whose molecular weights were measured were also dimeric (solvent given) examples are (ButOMgBr,THF)2(benzene), (Et3COMgBr,THF)2(benzene), (Et2MeCOMgBr,Et2O)2(ether), (Et2MeCOMgl,Et2O)2(ether), (Me2PrnCOMgl,Et2O)2(ether), t-Butoxymagnesium bromide-diethyl ether complex has also been prepared from magnesium bromide and both Mg(OBut)2 and MeMgOBut. The 1H n.m.r. spectra of several of the compounds described are anomalous in unexplained ways.

Process for the preparation of Tetrahydrofuran and/or Homologues thereof

Abstract: 1,170,222. Tetrahydrofurans. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 10 June, 1968, No. 27444/68. Heading C2C. A tetrahydrofuran of the general formula in which each R represents a hydrogen atom or a C 1 -C 5 alkyl group is prepared by (a) contacting a conjugated diolefin of general formula in an anhydrous, or substantially anhydrous, liquid medium, with a metal salt of an aliphatic carboxylic acid having 2-6 carbon atoms, together with a compound of divalent palladium, or with a divalent palladium salt of such a carboxylic acid alone; (b) separating from the reaction mixture one or more olefinically unsaturated 1,4-glycol acylates having the general formula in which at least one of the radicals R 1 and R 2 represents an acyl group having 2-6 carbon atoms, the other being the same or a hydrogen atom; (c) hydrogenating the ester obtained in (b) to give a saturated 1,4-glycol mono- and/or diacylate; and (d) converting the 1,4-glycol mono- and/or diacylate into the desired tetrahydrofuran, either directly by the action of an acidic catalyst in the presence of water or indirectly by first hydrolysing the mono- and/or diacylate and subsequently allowing the cyclization into the desired tetrahydrofuran to take place by methods known per se.

Co-ordination complexes of titanium(II)

Abstract: Titanium(II) chloride [or sodium tetrachlorotitanate(II)] and bromide react with methyl cyanide to yield the non-ionic complexes (TiX2,2MeCN)n which can be used as intermediates for the preparation of other complexes of the type TiX2,2L [L = pyridine, tetrahydrofuran, tetrahydropyran, ½(2,2′-bipyridyl), or ½2(1,10-phenanthroline)]. None of these products are magnetically dilute (µ ca. 1·0 B.M. at room-temperature) and they are probably halogen-bridged polymers in the solid state. Reaction of sodium tetrachlorotitanate(II) with trimethylamine resulted in oxidation of the halide and the formation of TiCl3,2NMe3. Similar oxidations occurred when pyridine reacted with titanium(II) chloride or bromide.

The infrared and Raman spectra of alkylzinc halides and related compounds

Abstract: Infrared and Raman spectra have been measured for dimethylzinc and diethylzinc in various ethers, and for ethylzinc iodide in diethyl ether. Infrared spectra are also reported for mixtures of dimethylzinc and diethylzinc with zinc chloride, bromide, and iodide in tetrahydrofuran. It is concluded that for all the alkylzinc halide systems the Schlenk equilibrium lies predominantly on the side RZnX. The infrared spectra of a number of solid alkylzinc adducts have been measured, and the trends in the zinc–carbon stretching frequencies are briefly discussed.

Zinc and magnesium derivatives of decaborane

Abstract: Organozinc compounds such as Me2Zn, Et2Zn, and Ph2Zn react at room temperature with decaborane in diethyl ether or tetrahydrofuran to yield the corresponding hydrocarbon (MeH, EtH, and PhH) and ZnB10H12,xS (where x= 1·3–2·0 and S is a molecule of ether solvent). The products are considered to be further examples of neutral 6,9-internally bridged derivatives of decaborane and to contain direct Zn–B bonds. The compounds ZnB10H12,xS ionise in aqueous or alcoholic solutions to give the dianion [(B10H12)2Zn]2–. The ultraviolet, infrared, and nuclear magnetic resonance spectra of these compounds have been recorded and their structures and probable topology are discussed. A related reaction of decaborane with diethylmagnesium at low temperatures yields the compound MgB10H12, 2Et2O but this decomposes in hydroxylic solvents with evolution of hydrogen. Dimethylmercury does not react with decaborane even on prolonged refluxing in diethyl ether.

Influence of dioxane on the anionic polymerization of styrene in benzene

Abstract: : It has been known that small amounts of polar solvents, such as ethers have a marked effect on the rate of anionic polymerization in a basically nonpolar medium. The only detailed kinetic study on this type of system was carried out by Bywater and Worsfold using small amounts of tetrahydrofuran (THF) in benzene. In this study it was found necessary to postulate the successive formation of a mono-etherate and a di-etherate of polystyryllithium, both active in polymerization, as the THF concentration was increased up to about 0.1 molar in benzene. Dioxane is often used in similar polymerization systems, and since this ether has a low dielectric constant (2.2) and essentially zero dipole moment, it is of obvious interest to study etherate formation with it as additive in order to provide information on the factors which give rise to specific ether solvation in anionic systems. (Author)

Cation-exchange separation of scandium from the rare-earth elements.

Abstract: From certain organic solvents containing organic phosphorus compounds such as trioctylphosphine oxide (TOPO), bis(2-ethylhexyl)orthophosphoric acid (HDEHP), or tri-n-butylphosphate (TBP) and hydrochloric acid, scandium is much less retained on the strongly acidic cation-exchange resin Dowex 50 than are all other members of the rare-earth group. Thus on this resin in a medium which is 95% tetrahydrofuran, 5% 6 M hydrochloric acid, and 0.1 M TOPO, the separation factor for scandium-rare earths is greater than 4 × 103 (corresponding to distribution coefficients of 4 × 103 for all the other rare-earth elements). By the use of this system a complete and highly effective separation of tracer and macro quantities of scandium from the rare earths can be achieved on a column of this exchanger. Among the organic solvents investigated, tetrahydrofuran gives the best results. The effectiveness of the organic extractants increases in the order TBP < HDEHP < TOPO