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.

Synthesis and Characterization of New Highly Organosoluble Poly(ether imide)s Bearing a Noncoplanar 2,2‘-Dimethyl-4,4‘-biphenyl Unit and Kink Diphenylmethylene Linkage

Abstract: Two new bis(ether anhydride)s, 2,2'-dimethyl-4,4'-bis[4-(3,4-dicarboxyphenoxy)]biphenyl dianhydride (4A) and bis[4-(3,4-dicarboxy phenoxy)phenyl]diphenylmethane dianhydride (4B), were prepared in three steps starting from nitrodisplacement of 4-nitrophthalonitrile with 2,2'-dimethylbiphenyl-4,4'-diol and bis(4-hydroxyphenyl)diphenylmethane, respectively, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile)s and subsequent dehydration of the resulting bis(ether diacid)s. A series of new highly organosoluble poly(ether imide)s were prepared from the bis(ether anhydride)s and various diamines by conventional two-stage synthesis. The resulting poly(ether imide)s had inherent viscosities in the range of 0.55-0.81 dL.g -1 . GPC measurement revealed that the polymers exhibited number-average molecular weight and weight-average molecular weight up to 45 000 and 82 000, respectively. All the polymers showed typical amorphous diffraction patterns. Almost all the poly(ether imide)s showed excellent solubility and readily dissolved in various solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and chloroform. These polymers had glass transition temperatures in the range of 224-256 °C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight loss recorded above 489 °C in nitrogen. The isothermal gravimetric analysis results demonstrated that these poly(ether imide)s showed weight losses of 7.0-10.5% after isothermal aging at 350 °C in static air for 20 h. These tough and flexible polymer films could be easily obtained by solution cast from the DMAc solution. These polymer films had tensile strength of 84-116 MPa and tensile modulus of 1.9-2.7 GPa.

Low-Temperature 13C-NMR Spectra of 6Li- and 13C-Labelled Sulfur- and Selenium-Substituted Organolithium Derivatives†‡§

Abstract: The 13C-NMR spectra of 19 different, singly, doubly, and triple 13C-labelled α-sulfur- and α-selenium-substituted 6Li-derivatives generated from methyl and phenyl thioethers, thioacetals, trithio-orthoesters and from their selenium analogues have been recorded in ethereal solutions (tetrahydrofuran (THF), 2-methyltetrahydrofuran (MTHF) at temperatures between −30° and −110°. The effects of H/Li-exchange upon chemical shifts and coupling constants, as well as the values and multiplicities of Li, 13C-coupling are interpreted in vie wof crystal structures of some of the same compounds. In two thirds of the cases studied, the H-decoupled 13C-NMR signals observed below −80° were triplets, proving that the C-atoms are bonded to single 6Li-atoms. This is compatible either with monomeric or with dimeric, heteroatom-bridged structures. The direct 1H, 13C- and 13C, 13C-coupling constants (1J) decrease, the 13C, 77Se-coupling constants increase upon lithiation. More striking is that the geminal coupling 13C-S-13C (2J) is too small to be observed in the non-metalated species, while it ranges from 3.7 to 7.5 Hz in the lithiated derivatives. These observations may be interpreted as resulting from delocalization of electron density from the carbonionic center towards the adjacent heteroatom.