Preparation conditions and properties of cellulose solutions in DMAA containing 7–8% lithium chloride are considered. Investigation
of the optical anisotropy and structure of cellulose solutions in this solvent confirms that the LS state is attained with
an increase in the concentration of cellulose. On the basis of these cellulose solutions, fibers not ranking below viscose
fibers in mechanical properties are prepared. The use of a mixed solution of 95% cellulose and 5% poly(amidobenzimidazole)
in DMAA containing 7% lithium chloride makes it possible to prepare films and fibers whose strength is more than two times
greater than the strength of cellulose hydrate fibers. The deformation-driven orientation and supramolecular structure of
fibers and films are studied by spectroscopy and small-angle scattering of polarized light. 相似文献
Conclusions A method was developed for the synthesis of vinyl alkyl sulfides by the nucleophilic addition of thiols to acetylene in aprotic dipolar solvents, like hexamethylphosphoric triamide and dimethyl sulfoxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 956–957, April, 1972. 相似文献
Reactions of aliphatic branched aldehydes with proline in dimethyl sulfoxide or acetonitrile solution afford oxazolidin-5-ones with high diastereoselection. Linear aldehydes afford aldolic/crotonic condensation products; with short reaction times, the presence of Oxazolidinones can be detected in the pmr spectra. Acyclic aminoacids and branched aldehydes yield a reaction mixture the pmr and ir spectra of which give evidence for iminic-oxazolidinone equilibria. The structure of (2R,5S)-2-trichloromethyl-1-aza-3-oxabiciclo-[3.3.0]octan-4-one has been confirmed by X-ray diffraction analysis. 相似文献
The solvation of a variety of ions by the dipolar aprotic solvents acetonitrile, sulfolane, and dimethylsulfoxide was studied through the influence of salts on the proton magnetic resonance chemical shifts of the solvents. In the case of acetonitrile the results were supplemented with infrared measurements, which showed that in general anions affect only the C–H and cations both the C–C and particularly the CN stretching frequencies of acetonitrile. The results are discussed in conjunction with transport and other data already in the literature. Current views on the structure of these solvents are summarized.From the Ph.D. thesis of this author, University of Pittsburgh, 1972. 相似文献
The use of ortho-chloranil (o-CA) as an electrochromic material requires three conditions to operate properly: (1) the reversibility of the electronic transfer of the reaction ; (2) the formation of a visible-light absorbing charge-transfer complex between o-Ca− and the counterion M+, and (3) the use of an insoluble salt o-CA−M+ as a film adherent to the electrode surface. The behavior of the redox o-CA/o-CA− couple has been investigated in different solvents and in the presence of several alkaline and alkaline earth cations (Mz+). The reversibility of the electron transfer and the formation of an adhesive salt layer on the electrode are strongly related to the counter ion Mz+. The ion-pair formation depends on the solvent and particularly on its weak electron donor character. The best electrochromic properties of o-CA were obtained in 0.1 M NaClO4 acetonitrile solutions. 相似文献
The reaction kinetics of halogenated compounds with tertiary amine groups attached at an acrylic macromolecular chain have ben studied. Three acrylic polymers were used. Two of them have mainly a structural unit of N, N-dimethylaminopropylacrylamide and the third is poly(N,N-dimethylaminoethylmethacrylate). Dimethylformamide, dimethylacetamide, and dimethylsulfoxide (DMSO) were used as dipolar aprotic solvents. Benzyl chloride and allyl chloride were considered as halogenated compounds with increased reactivity. The reaction kinetics depend on the polymer and halogenated-compound structures as well as the nature of the solvent. In the most of the cases the reactions carried out on polymers are accompanied by self-accelerating processes, with the exception of DMSO, which obviously has normal second-order kinetics. The reaction of polymers containing units of N,N-dimethylaminopropylacrylamide are compared with one having a low molecular weight, for instance N,N′-bis(3-dimethylaminopropyl)glutaramide. 相似文献
Dissociation of trifluoromethanesulfonic acid in non-aqueous solvents has been investigated mainly by conductometry and compared with that of p-toluenesulfonic, methanesulfonic, fluorosulfuric and perchloric acids. The solvents used are dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, n-butyronitrile, propylene carbonate, acetonitrile, nitromethane, methyl isobutyl ketone and acetic acid. Trifluoromethanesulfonic acid is completely dissociated in rather basic solvents such as dimethyl sulfoxide, dimethylacetamide and dimethylformamide, while it is associated to some extent in the other solvents, especially in methyl isobutyl ketone and acetic acid. The strength of trifluoromethanesulfonic acid is almost the same as that of perchloric acid in all the solvents. Dissociation constants of the other acids are also obtained. 相似文献
Tertiary amines are utilized extensively as non-nucleophilic proton scavengers for a number of organic transformations. Herein we report the efficient syntheses of tertiary alkyl amines from their corresponding alkyl nitriles in the presence of a heterogeneous palladium catalyst and a source of dihydrogen in aprotic solvents. The reaction is atom economic, the conditions are mild, and the isolated yields are virtually quantitative. The degree of amine alkylation shows some solvent dependency; in polar protic solvents such as ethanol or methanol, the reaction affords a mixture of products with the secondary alkyl amine as the major product. 相似文献
The visible absorption spectra of CoCl2 in binary mixtures of acetone, dmf, dma and dmso with H2O show the existence of configuration equilibria between tetrahedral (T) and octahedral (O) species. Linear correlations between the values of log K (K = [O]/[T]) and the mole fraction of H2O,
w, have been observed in all the systems under study; their slopes decrease linearly with an increase of the donor number, DN, of the organic component of the mixture. The formation of octahedral species is enthalpy favoured but entropy disfavoured. It was found that both H and S values change linearly with
w and the slopes of these relationships depend clearly on the DN values. 相似文献
Oxidative dissolution of nickel in the benzyl halogenide – dipolar aprotic solvent system in the presence of air oxygen proceeds with the formation of benzaldehyde, benzyl alcohol, 1,2-diphenylethane, and trace amounts of 4,4'-ditolyl. Spectrophotometry studies have revealed that the oxidation products are formed in the solution rather than at the nickel surface. It has been shown that the oxygen adsorbed at the nickel surface practically does not pass into the solution. 相似文献