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991.
Christopher J. Chandler Leslie W. Deady James A. Reiss Vasilios Tzimos 《Journal of heterocyclic chemistry》1982,19(5):1017-1019
The preparation of a series of macrocycles, formed by reaction of HO-(-CH2-CH2-O-)nH with 1,10-phenanthroline-2,9-dicarbonyl chloride (n = 2,3,4) and 1,8-naphthyridine-2,7-dicarbonyl chloride (n = 3,4), is described. An improved synthetic route to 2,7-dimethyl-1,8-naphthyridine 9 is also reported. 相似文献
992.
The compounds CdCr2S4 and CoCr2S4 have been hot pressed into disks that are highly transparent in the infrared. Stoichiometry has been altered by varying the ratio, where M2+ is Cd2+ or Co2+. The effects of nonstoichiometry on optical transmission were determined. Excess M2+ attenuates the transmission much more than excess Cr3+. 相似文献
993.
R. Arshady G. W. Kenner A. Ledwith 《Journal of polymer science. Part A, Polymer chemistry》1974,12(9):2017-2025
Details are given of the synthesis and purification of p-acetoxystyrene and its solution and suspension copolymerization with styrene. Reactivity ratios, evaluated by the Tidwell-Mortimer method, were r1 (p-acetoxystyrene) = 1.18, and r2 (styrene) = 0.88 for (bulk) solution copolymerization. Corresponding values of the reactivity ratios for suspension copolymerization were, within experimental error, indistinguishable from unity. Thus the copolymer composition is governed simply by the monomer feed composition. Use of a specially designed reactor vessel permits convenient suspension copolymerization of styrene, p-acetoxystyrene, and divinylbenzene to give crosslinked resins having comparatively narrow particle size distributions. Acetoxy groups in the crosslinked resin are cleaved by hydrazine hydrate under very mild conditions to give crosslinked polystyrenes having phenolic groups which, in turn, provide a useful alternative to the more usual chloromethylated polystyrene resins for solid-phase peptide synthesis. 相似文献
994.
A new transient in the photocyclization reaction of diphenylamines to carbazoles has been detected. It absorbs at 430 nm and is assigned to the excited triplet state of the intermediate photoproduct 11,12-dihydrocarbazole. 相似文献
995.
2,5-Dihydro-5-oxo-1,2,4-triazine and some of its alkylated derivatives have been prepared. Nmr spectroscopic analysis has established that the 2,5-dihydro-5-oxo tautomers are preferred over the 4,5-dihydro-5-oxo ones. This preference, and the behavior of 1,2,4-triazines in some other chemical reactions has been interpreted in terms of electron-electron repulsions between the lone pairs of electrons of N1 and N2 in this ring system. 相似文献
996.
W. K. Fischer 《Fresenius' Journal of Analytical Chemistry》1967,227(2):116-120
Zusammenfassung Es wird auf eine bisher nicht beachtete Fehlermöglichkeit bei der analytischen Untersuchung und Weiterverwendung von membranfiltrierten Lösungen hingewiesen. Die üblichen Membranfilter enthalten zur Hydrophilisierung bestimmte Mengen anionaktiver Tenside, die sich nur in wechselndem Ausma\e vor dem Gebrauch eluieren lassen. Bei der Untersuchung von membranfiltrierten Flu\-, Grund- und Trinkwasserproben findet man dadurch zu hohe Tensidkonzentrationen und bei der Austestung und Verwendung sterilfiltrierter Wirkstofflösungen u. a. können betrÄchtliche Störungen eintreten. Von Fall zu Fall ist darum eine sorgfÄltige Versuchskontrolle hinsichtlich einer spezifischen Tensidwirkung nötig.
Summary Reference is made to a source of error so far unknown in analytical examinations of aqueous membrane-filtered solutions. Membrane filters usually contain a certain amount of anionic surface-active substances for hydrophilizing purposes. These substances are only partly eliminated before the use of the filter. Therefore, in samples of membrane-filtered river, underground and tap water concentrations are found higher than the actual detergent content. There may also be interferences with the testing of bio-active substances, for instance of antibiotics. Advice is given to control carefully the possible specific effect of surface-active substances during these experiments.相似文献
997.
We present a study of single color (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of H2O, D2O, and HDO via several Rydberg states lying in the energy range from 80 000 to 86 000 cm−1. Photoelectron spectra (PES) show that the corresponding cations can be vibrationally state-selected for most vibrational states. The exception is the bend of H2O+ and HDO+, where mixing in the REMPI intermediate level results in weak ion intensity and only 50% state purity. 相似文献
998.
Tertiary phosphine oxides have been prepared in excellent yield from primary alkyl halides or aromatic halides and activated sodium phosphinates obtained by reaction of dialkyl phosphine oxides with complex bases (NaNH2/tBuONa). This reaction has been successfully applied to soluble and cross-linked bromopolystyrenes and to macroporous polystyrenes with bromooctyl substituents giving polymers which contain pendant phosphine oxide groups. 相似文献
999.
F W Wang 《Macromolecules》1976,9(1):97-101
An equation for the translational diffusion coefficient of block copolymers in dilute solution has been obtained by modifying Zimm's equation for homopolymers to take into account the existence of dissimilar segments in block copolymers. Illustrative calculations for homopolymers and block copolymers have been made and the results for homopolymers have been compared with experiments and with the calculations of Yamakawa and Fujii. A procedure has been proposed to determine the molecular weight of a block copolymer from measurements of its limiting viscosity number and its sedimentation coefficient or translational diffusion coefficient. 相似文献
1000.
Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C6H5)4][SnF3] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)5SnF3]? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)5THF only one pure triiodostannidometalate(O) Complex, [N(C2H5)4][Cr(CO)5SnJ3], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)5SnClX2]? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX2-insertion reactions of the [M(CO)5Cl]? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes. 相似文献