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161.
Eles J Kalaus G Greiner I Kajtár-Peredy M Szabó P Keserû GM Szabó L Szántay C 《The Journal of organic chemistry》2002,67(21):7255-7260
The first syntheses of the alkaloids (-)-mehranine (3), (+)-voaphylline/conoflorine (4), (+)-N(a)-methylvoaphylline/hecubine (5), and (-)-lochnericine (2) were achieved by stereoselective epoxidation starting from (-)-tabersonine (1), through intermediates with the aspidospermane and quebrachamine skeleton. 相似文献
162.
Ferenc F. Gaál Vukadin M. Leovac Branislava Dj. Avramovi 《Fresenius' Journal of Analytical Chemistry》1973,266(5):355-357
Summary Tertiary amines and salts of organic acids in acetic anhydride with 5% of acetic acid were titrated applying a biamperometric indicating system consisting of a polarised or unpolarised pair of tin electrodes by means of 0.1 N perchloric acid in glacial acetic acid. Amounts of 15.4–29.8 mg were analysed with average deviations of <0.6%, the results obtained being in a good agreement with those of potentiometry. The biamperometric end-point detection using an indicating system of polarised pair of tin electrodes can be applied for coulometric determinations of these bases with satisfying accuracy. By means of anodic generation of hydrogen ions in the presence of hydroquinone amounts of 0.5–1.0 mg were titrated with average deviations of < 1.3%. The results obtained were compared with those obtained of catalytic thermometric and photometric titrations.
Biamperometrische Neutralisationstitrationen in nichtwärigen Lösungsmitteln unter Anwendung eines Zinn-Elektrodenpaares als Indicatorsystem
Zusammenfassung Tertiäre Amine und Salze organischer Säuren werden in Acetanhydrid mit 5% Essigsäure durch Titration mit einer 0,1 N Lösung von Perchlorsäure in Essigsäure bestimmt. Das verwendete biamperometrische Indicatorsystem besteht aus einem Paar polarisierter oder nichtpolarisierter Zinnelektroden. Mengen von 15,4–29,8 mg wurden mit einer mittleren Abweichung von <0,6% analysiert. Die Ergebnisse stimmen gut mit denen von potentiometrischen Titrationen überein. Die biamperometrische Endpunkttechnik mit polarisierten Zinnelektroden kann für coulometrische Bestimmungen dieser Basen mit zufriedenstellender Genauigkeit benutzt werden. Durch anodische Erzeugung von Wasserstoffionen in Gegenwart von Hydrochinon wurden Mengen von 0,5–1,0 mg mit einer mittleren Abweichung von < 1,3% titriert. Die Ergebnisse wurden mit denen von katalytisch-thermometrischen und photometrischen Titrationen verglichen.相似文献
163.
Jiří Kohout Mária Kabešová Prof. Dipl.-Ing. Dr. Ján Gažo 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1011-1018
The infrared spectra of thiocyanato-copper(II) complexes of the type Cu(NCS)2
L
2 with all isomeric picolines and lutidines (L) as well as those of the type Cu(NCS)2
L
3 withL=3- and 4-picoline, 3,4- and 3,5-lutidine were measured. The behaviour of the (CN) stretching vibrations of the Cu(NCS)2
L
2 complexes led to conclusions on the different kind of coordination of the NCS groups in dependence on the ligandL. The mutually conditioned strength of the Cu–NCS and Cu–N(L) bonds in the equatorial plane, especially in the presence of ligandsL with the steric effect, was determined from the frequency shift of the Cu–NCS and Cu–N(L) stretching vibrations with regard to the vibrations for Cu(NCS)2(pyridine)2.
Mit 1 Abbildung 相似文献
Mit 1 Abbildung 相似文献
164.
Robin Zuluaga Jean-Luc Putaux Adriana Restrepo Iñaki Mondragon Piedad Gañán 《Cellulose (London, England)》2007,14(6):585-592
Cellulose microfibrils have been prepared from banana rachis using a combination of chemical and mechanical treatments. The
morphology and structure of the samples were characterized using transmission electron microscopy, atomic force microscopy,
and X-ray diffraction. Fourier-transformed infrared spectroscopy (FTIR) was used to characterize the chemical modifications
of the samples after each treatment. Suspensions of bundled or individualized 5-nm-wide microfibrils were obtained after homogenization
(PH) whereas an organosolv (PO) treatment resulted in shorter aggregates of parallel cellulose microcrystallites. The sharper
rings in the X-ray diffraction pattern of the PO-treated sample suggest a higher crystallinity due to a more efficient removal
of hemicelluloses and dissolution of amorphous zones by the acid treatment. Both microfibrils and microcrystals prepared by
both methods can be used as reinforcing filler in nanocomposite materials. 相似文献
165.
Molecular dynamics simulation of a linear soft polymer has been performed and the free volume properties of the system have been analyzed in detail in terms of the Voronoi polyhedra of the monomers. It is found that there are only small density fluctuations present in the system. The local environment of the monomers is found to be rather spherical, even in comparison with liquids of atoms or small molecules. The monomers are found to be, on average, eight coordinated by their nearest geometric neighbors, including intra-chain and inter-chain ones. The packing of the monomers is found to be rather compact, in a configuration of 1900 monomers there are, on average, only three voids large enough to incorporate a spherical particle as large as a monomer, indicating that the density of the large vacancies in the system is considerably, i.e., by a few orders of magnitude lower than in molecular liquids corresponding to roughly the same reduced densities. 相似文献
166.
al-Maharik NI Kaltia SA Mutikainen I Wähälä K 《The Journal of organic chemistry》2000,65(8):2305-2308
Unique C-C-bridged bis-isoflavones 5, 8, and 9 were obtained by reaction of 2-bromomethyl-7,4'-dimethoxyisoflavone 4 with ethyl cyanoacetate anion or tetraethylammonium cyanide or by Pd-catalyzed ethoxycarbonylation, respectively. The phenolic carboxylic acid 7 is available from 5 in two steps. 相似文献
167.
In connection with an optimization problem, all functions ?: In → with continuous nonzero partial derivatives and satisfying for all xi, xj ≠ I, i, j = 1,2,…, n (n > 2) are determined (I is an interval of positive real numbers). 相似文献
168.
P. Kratochvíl B. Smola I. Stulíková P. Vostrý F. Jandoš J. Šedivec 《Czechoslovak Journal of Physics》1985,35(3):257-260
Static softening of AISI 321 steel after cold and hot deformation characterizing the industrial thermomechanical treatment was studied by means of tensile tests and TEM. The deformation temperature, the strain and the grain size were the main parameters determining the final softening. The results can be applied for optimization of the solution annealing. 相似文献
169.
J. Kohout M. Quastlerová-Hvastijová J. Gažo 《Monatshefte für Chemie / Chemical Monthly》1973,104(3):779-783
Zusammenfassung Die Ligandenfeldspektren der Komplexe des Typs Cu(NCO)2
L
2 (L=Ligand der Chinolin- bzw. Isochinolingruppe) im festen Zustand wurden aufgenommen. Das Spektrum des Komplexes Cu(NCO)2(Chin)2 weist eine einzige Bande auf und deutet auf eine pseudooktaedrische Struktur. Die Spektren der übrigen Komplexe enthalten hingegen neben den Hauptbanden auch Schultern bzw. ist die anwesende Bande zusammengesetzt, so daß diese Spektren mit einer planaren Struktur im Einklang sind. Die annähernden Werte für den Parameter 10Dq wurden berechnet; sie liegen im Bereich von 7,1 bis 7,8 kK.
Mit 1 Abbildung
6. Mitt.:M. Quastlerová-Hvastijová, J. Kohout undJ. Gao, Z. anorg. allgem. Chem., im Druck. 相似文献
Ligand field spectra of some cyanato-copper(II) complexes with ligands from the quinoline- and isoquinoline group
The ligand field spectra of complexes of the type Cu(NCO)2 L 2 (L=ligand from the quinoline or isoquinoline group) in the solid state were recorded. Only the spectrum of Cu(NCO)2(Quin)2 exhibits a single band and indicates a pseudooctahedral structure, while the spectra of the remaining complexes also contain shoulders in addition to the main band, or this band is composite, thus being in accordance with a planar structure. The approximate values of the parameter 10Dq were calculated and found to be in the range of 7.1 to 7.8 kK.
Mit 1 Abbildung
6. Mitt.:M. Quastlerová-Hvastijová, J. Kohout undJ. Gao, Z. anorg. allgem. Chem., im Druck. 相似文献
170.
N. V. Gérbéléu V. B. Arion Yu. A. Simonov V. E. Zavodnik K. I. Turté S. S. Stavrov A. A. Pasynskii O. G. Ellert D. I. Grédinaru M. S. Byrke 《Theoretical and Experimental Chemistry》1991,27(3):327-332
Sodium acetylacetonate reacts with S-metliylisothiosemicarbazidium nitrate and Fe(NO3)3 · 9H2O in ethanol to make [Fe(HL)NO]NO3, in which H3L is bis(S-methyl-isothiosemicarbazone)-2,4-puntandione. The [Fe(HL)NO]+ cation has a square pyramidal structure with the HL2- arranged around the central ion in the basal plane and the nitrogen atom of the NO group in the apical position, with the iron atom diverging from the plane of the base of the pyramid by 0.477 Å. The FeN0 moiety has a linear structure (FeNO = l72.7°). XRD, IR, and Mössbauer spectroscopy have been combined with calculations on the electronic structure to demonstrate that the Fe-NO bond is covalent.Chemical Institute, Academy of Sciences of Moldavian SSR. Applied Physics Institute, Academy of Sciences of the Moldavian SSR. Kishinev. Institute of Crystallography, Academy of Sciences of the USSR. Kurnakov Institute for General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No, 3, pp. 376–381, May–June, 1991. Original article submitted February 18, 1991. 相似文献