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.

Polymer conformations of gas-hydrate kinetic inhibitors: A small-angle neutron scattering study

Abstract: We have used small-angle neutron scattering to characterize the polymer conformations of four nonionic water soluble polymers: poly(ethylene oxide), poly(N-vinyl-2-pyrollidone), poly(N-vinyl-2-caprolactam), and an N-methyl, N-vinylacetamide/N-vinyl-2-caprolactam copolymer. The last three of these are able to kinetically suppress hydrate crystallization, and their inhibitor activity ranges from moderate to very effective. This attribute is of significant commercial importance to the oil and gas industry, but the mechanism of the activity is unknown. The dilute-solution polymer conformation in a hydrate-forming tetrahydrofuran/water fluid shows little difference among the four polymers: the majority of the scattering is that expected for a polymer in a good solvent. Each solution also exhibits some additional low-q scattering which we attribute to aggregates. In the presence of a hydrate-crystal/liquid slurry, the three inhibitor polymers significantly change their conformation. Utilizing results from our p...

Synthesis and polymerization of N‐[4‐N′‐ (α‐methylbenzyl)aminocarbonylphenyl]maleimide

Abstract: A novel type of optically active N-[4-N′-(α-methylbenzyl)aminocarbonylphenyl]maleimide [(R)-MBCP] was synthesized from maleic anhydride, p-aminobenzoic acid, and (R)-methylbenzylamine. Radical homopolymerization of (R)-MBCP was performed in tetrahydrofuran (THF) at 50 and 70°C for 24 h to give optically active polymers having [α]25D = -141° and -129°, respectively. Anionic polymerization of (R)-MBCP with n-butyllithium in THF and N,N-dimethylformamide gave an optically active polymer having −78 to −81° of [α]25D. Radical copolymerizations of (R)-MBCP (M1) were performed with styrene (ST, M2) and methyl methacrylate (MMA, M2) in THF at 50°C. The monomer reactivity ratios (r1, r2) and the Alfrey-Price Q-e values were determined as follows: r1 = 0.009, r2 = 0.091, Q1 = 1.30, e1 = 1.87 in the (R)-MBCP-ST; r1 = 0.27, r2 = 1.21, Q1 = 0.93, e1 = 1.46 in the (R)-MBCP-MMA system. Chiroptical properties of the polymers were also investigated. © 1992 John Wiley & Sons, Inc.

Isoprene polymerization by organometallic compounds. II

Abstract: Dispersions of metallic lithium, sodium, and potassium and some of their organoderivatives were used to initiate the polymerization of isoprene in several solvents. The propagating species in all cases were ion pairs of the type . The structure of the resultant polyisoprene depends on the character of the propagating pair. This in turn depends mainly on the counterion M+ and the solvent type. One quality of this ion pair which is of utmost importance is its ionic character (or degree of charge separation). In solvents such as diethyl ether and tetrahydrofuran, where we might expect large charge separation in the ion pair, all initiatiors produce similar, though not necessarily identical, polymer structures comprising 1,2 -3,4-, and trans-1,4-adducts. With potassium-dependent initiators, very nearly the same polymer structure is obtained in hydrocarbons as in the more basic ethers, attesting to the highly ionic character of the potassium-carbon bond; this might perhaps be considered as the “limiting anionic behavior”. Sodium has smaller inherent ionic-character and is more sensitive to changes in solvent basicity, but still it parallels the behavior of potassium. With lithium, the most covalent of the alkali metals, a dramatic change in behavior occurs when polymerization is conducted in hydrocarbon media; a 93% cis-1,4-,7% 3, 4-polyisoprene structure is obtained. This may be merely a limiting structural from at the low end of the scale of ionic character of the propagating ion-pair. The steric factors arising from complexes formed between the propagating ion-pair. The steric factors arising from complexes may also have an important influence on the polymer structures product in the various solvents. A continuous seriese of polyisoprene structures intermediate between those formed in hydrocarbons with Li and the limiting “anionic structure” can be obtained by use of such solvents as phenyl ether or anisole, or by judicious choice of appropriate hydrocarbon–solvent ratios with a number of suitable cosolvents.

Synthesis, Characterization, and Ethylene Polymerization Behavior of 8-(Nitroarylamino)-5,6,7-trihydroquinolylnickel Dichlorides: Influence of the Nitro Group and Impurities on Catalytic Activity

Abstract: The series of N-(5,6,7-trihydroquinolin-8-ylidene)nitroarylamine ligands (L1–L4) was prepared and used to synthesize the chloro-bridged dinickel complexes (Ni1–Ni4) and the bis-ligated mononickel(II) complex (Ni5) in good yield. Molecular structures of Ni1, Ni2, Ni4, and Ni5 were confirmed by single-crystal X-ray diffraction analysis, revealing a pseudosquare–pyramidal geometry around nickel in the chloro-bridged complexes (Ni1, Ni2, and Ni4) and a distorted octahedral geometry at the nickel atom in the bis-ligated complex (Ni5). Upon treatment with ethylaluminum sesquichloride (EASC, Et3Al2Cl3) or methylaluminoxane (MAO), all nickel complexes exhibited high activities (up to 4.05 × 106 g (PE) mol–1 h–1) for ethylene polymerization. Moreover, heterocyclic impurities such as tetrahydrofuran (THF) and pyridine, often detected in common solvents, were added to the catalytic system of precatalyst Ni2 under controlled conditions and were found to have a negative influence on the catalytic behavior during ethyl...