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1.
The crystal structure of NF4BF4 has been reexamined. The low-temperature X-ray structure and solid-state 19F MAS NMR spectra are in agreement with the conclusions reached from the vibrational spectra, that solid NF4+ salts contain only tetrahedral NF4+ cations. The alleged observation of two kind of nontetrahedral NF4+ cations in several previous crystal structures is attributed to incorrectly solved structures and, possibly, problems caused by disorder or twinning. It is further evidence for the dangers of over-reliance on crystal structures. Flawed crystal structures can give rise to either bad or unwarranted theory. 相似文献
2.
G. Czupińska 《Journal of Thermal Analysis and Calorimetry》2000,60(1):199-202
The phase equilibria in the part of the ternary system YPO4–K3PO4–Mg3(PO4)2 over the composition range YPO4–K3PO4–KMgPO4 were examined and determined by differential thermal analysis, X-ray powder diffraction and microscopic analysis in reflected
light.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
D. Piotrowska T. Znamierowska I. Szczygieł 《Journal of Thermal Analysis and Calorimetry》2013,113(1):121-126
The phase equilibria occurring in the ErPO4–K3PO4 system were investigated by the thermal analysis, FTIR, and X-ray powder diffraction methods. On the basis of obtained results, the related phase diagram is proposed. This system includes one intermediate compound, K3Er(PO4)2; the double phosphate melts incongruently at 1355 °C and occurs in two polymorphic forms; transformation β/α-K3Er(PO4)2 proceeds at 420 °C. The eutectic occurs at the composition of 58.5 wt% K3PO4, 41.5 wt% ErPO4 at 1317 °C. 相似文献
4.
W. Szuszkiewicz E. Radomińska T. Znamierowska P. Wilk 《Journal of Thermal Analysis and Calorimetry》2013,111(1):63-69
The phase equilibria occurring in the YPO4–Rb3PO4 system were investigated by thermoanalytical methods, X-ray powder diffraction, and ICP-OES. On the basis of the obtained results, its phase diagram is proposed. It was found that the system includes two intermediate compounds Rb3Y(PO4)2 and Rb3Y2(PO4)3. The Rb3Y(PO4)2 compound melts congruently at 1300 °C. The Rb3Y2(PO4)3 orthophosphate was previously unknown. This intermediate compound is high-temperature unstable and decomposes within the temperature range 1300–1330 °C to YPO4 and Rb3Y(PO4)2. The decomposition process is irreversible. It was found that the Rb3Y2(PO4)3 orthophosphate is isostructural with Rb3Yb2(PO4)3 and crystallizes in the cubic system (a = 1.70226 nm). 相似文献
5.
Lebedukho A. Yu. Kuritsyn L. V. Sadovnikov A. I. 《Russian Journal of General Chemistry》2004,74(2):222-224
Equations relating the N-acylation rate constants of glycine, L--alanine, DL-threonine, and L-proline with 4-nitrophenyl 4-nitrobenzoate in water-acetonitrile, water-2-propanol, and water-2-methyl-2-propanol solvents to the composition of the medium were obtained, and reaction rate constants in water were calculated. 相似文献
6.
L. M. Babkov I. I. Gnatyuk G. A. Puchkovskaya S. V. Trukhachev 《Journal of Structural Chemistry》2004,45(3):374-381
The conformational lability of 4-ethyl-4-cyanobiphenyl molecules in solid crystal (SC) and isotropic liquid (IL) states was investigated by IR spectroscopic techniques (experiment and theory). IR absorption spectra were measured at 28°C–95°C in the frequency range 400 cm–1–4000 cm–1. Spectrum simulation was performed using the fragment method with allowance for the conformational fluctuations of molecules. The experimental and calculated spectra were compared and analyzed, and it was shown that in the IL, the samples are mixtures of conformers. The temperature changes in the spectra in the stated range are caused by the conformational lability of molecules.Original Russian Text Copyright © 2004 by L. M. Babkov, I. I. Gnatyuk, G. A. Puchkovskaya, and S. V. TrukhachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 398–405, May–June, 2004. 相似文献
7.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1977,33(8):771-774
Far-infrared study on the NH4BrNH4I mixed crystals revealed the librational frequencies of 314 cm−1 for 1 (bromide):3 (iodide) and of 322 cm−1 for 1:1 crystals. The phase transitions of the 1:3 mixed crystal occurred at around 205 and 235 K. The potential barrier heights for the NH+4 librations have been estimated to be 3.58 and 3.83 kcal/mol for the 1:3 and 1:1 mixed crystals, respectively. 相似文献
8.
Different physical chemical methods were used to study the thermochemical processes in a system involving a natural phosphate and complex acid salts of ammonium sulphate. The products of decomposition of the double ammonium salt and the products of their interactions with the phosphate were identified. The formation of ammonium and calcium polyphosphates and the disproportionation of P3O 10 5? and P2O 7 4? to PO 4 3? and PO 3 ? were found to depend on the circumstances of the thermal interactions. 相似文献
9.
10.
C. J. Ballhausen 《Theoretical chemistry accounts》1963,1(4):285-293
Teltow'S [14,15] measurements of the permanganate bands are reanalyzed using the level scheme of Ballhausen and Liehr [2]. For KMnO
4 dissolved in KClO
4 the components of the first 1
T
2 state are found at 18050 cm–1 18078 cm–1 and 18043 cm–1. The breathing frequency of the MnO
–
4
unit is in this state 768 –1. The electronic origin of the second 1
T
2 state is found at 30723 cm–1 with a breathing frequency of 760 cm–1.Evidence is further found for a 1
T
1 state with its split components located at 14446 cm–1, 14526 cm–1 and 14600 cm–1. The breathing frequency is here found to be 800 cm–1.Finally for KMnO
4 dissolved in NaClO
4 there are indications that one or two spin-triplets are located near 13200 cm–1.
Zusammenfassung TeltowS Messungen des Permanganatspektrums [14, 15] werden mit Hilfe des Termschemas von Ballhausen und Liehr [2] von neuem analysiert. Für KMn 4 in KClO 4 findet man die zum ersten 1 T 2-Zustand gehörenden Komponenten bei 18050, 18078 und 18043 cm–1. Die Valenzschwingung des MnO – 4 liegt hier bei 768 cm–1. Der Ursprung des zweiten 1 T 2-Systems wird bei 30723 cm–1 gefunden, die dazugehörige Valenzfrequenz ist 760 cm–1.Bei 14446, 14526 und 14600 cm–1 liegen offenbar die Komponenten eines 1 T 1-Terms, wozu eine Valenzfrequenz von 800 cm–1 gehört.Schließlich findet man für KMnO 4 in NaClO 4 Anzeichen für ein oder zwei Spin-Tripletts um 13200 cm–1.
Résumé Les bandes d'absorption du permanganate, mesurées par Teltow [14,15], sont réanalysées à l'aide d'un système de termes proposé par Ballhausen et Liehr [2]. Pour KMnO 4 dans KClO 4, on trouve les composants du premier état 1 T 1 à 18050, 18078 et 18043 cm–1. La vibration symétrique du MnO – 4 dans cet état se situe à 768 cm–1. L'origine électronique du second état 1 T 2 est trouvé à 30723 cm–1, la fréquence oscillatrice correspondante est de 760 cm–1.Un état 1 T 1 avec ses composants à 14446, 14526 et 14600 cm–1 est mis en évidence, avec une vibration symétrique de 800 cm–1.Finalement, au cas du KMnO 4 dissous dans le NaClO 4, il y a des indications pour un ou deux triplets de spin vers 13200 cm–1.相似文献
11.
M. F. Butman L. S. Kudin V. B. Motalov D. A. Ivanov V. V. Sliznev K. W. Krämer 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(5):767-772
The thermodynamic stability of the LaBr 4 ? anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction $ LaBr_4^ - = Br^ - + LaBr_3 The thermodynamic stability of the LaBr4− anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The
experimental and theoretical enthalpies of the reaction were Δr
H°(298.15 K) = 302 ± 14 and 303 kJ/mol, respectively. The value Δf
H° (LaBr4−, g, 298.15 K) = −1105 ± 14 kJ/mol was recommended as the enthalpy of formation of the LaBr4− anion.
Original Russian Text ? M.F. Butman, L.S. Kudin, V.B. Motalov, D.A. Ivanov, V.V. Sliznev, K.W. Kr?mer, 2008, published in
Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 5, pp. 885–890. 相似文献
12.
G. Sh. Shekhtman E. I. Burmakin B. D. Antonov 《Russian Journal of Electrochemistry》2013,49(7):693-697
The lithium-conducting solid electrolytes in the Li4 ? 2x Cd x GeO4 (0 ≤ x ≤ 0.6) system are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The specimens with the highest conductivity have a γ-Li3PO4-derivative structure. The solid solutions with x = 0.15–0.25 are stable at the room temperature, whereas the specimens with x ≥ 0.3 decompose yielding Li2CdGeO4 below 310 ± 10°C. Li3.6Cd0.2GeO4 solid solution exhibits the highest conductivity (5.25 × 10?2 S cm?1 at 300°C). The factors, which affect the conductivity of synthesized solid electrolytes, are considered. 相似文献
13.
Michael Hartmann Rudolf Christian Erich Zbiral 《Monatshefte für Chemie / Chemical Monthly》1991,122(1-2):111-125
Summary While the reaction of the 4-oxo-Neu 5 Ac derivative2 a with tributoxy methyl zirconate led exclusively to equatorial 4-C-methyl derivative3 a, the analogous reaction with tetramethyl zirconate yielded a 3:2 mixture of both diastereoisomeres3 a and4 a. After removal of protecting groups the 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid5 a and 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-talo-2-nonulosonic acid6 a were obtained. The 4-C-methylene derivative was prepared by treatment of the same 4-oxo-derivative with CH2I2/Zn/Cp
2ZrCl2. Subsequent hydrogenation led to both epimeric 4-deoxy-4-C-methyl derivatives8 a and9 a. Final removal of protecting groups gave the 5-acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid10 a respectively the 5-acetamido-2,7-anhydro-4-C-methyl-3,4,5-trideoxy-D-glycero-D-talo-2-nonulosonic acid11 a. The -methylketosides of the 4-deoxy-4-C-methyl- (16) and 4-C-methylene-Neu 5 Ac (15) were prepared via the peracetylated derivatives to obtain modell substrates for enzymatic studies. Thus all free acids were tested for inhibition of CMP-sialate synthease. Only the 4-C-methylene compound15 showed most unexpectedly a strong competitive inhibition of this enzyme.
Strukturelle Abwandlungen an N-Acetylneuraminsäure, 19. Mitt.: Synthese der beiden Epimerenpaare der 4-C-Methyl- und 4-Deoxy-4-C-methyl- sowie des -Methylketosids der 4-Deoxy-4-C-methylen-N-acetylneuraminsäure. Verhalten gegenüber CMP-Sialat-Synthase
Zusammenfassung Während die Umsetzung des 4-Oxoderivates2 a mit (BuO)3 MeZr ausschließlich zur equatorialen 4-C-Methylverbindung3 a führt, wurde bei der Reaktion mitMe 4Zr ein 3:2-Gemisch der beiden Diastereomeren3 a und4 a erhalten. Das 4-C-Methylenderivat7 a wurde durch Reaktion derselben 4-Oxoverbindung mit CH2I2/Zn/Cp 2ZrCl2 erhalten. Eine anschließende Hydrierung (H2-Pd/C) führte zu einem trennbaren Germisch der beiden 4-Deoxy-4-C-methylderivative8 a und9 a. Diese Verbindungen konnten durch das Entfernen der Schutzgruppen einerseits in die 5-Acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonsäure10 a und 5-Acetamido-2,7-anhydro-4-C-methyl-3,4,5-tridoxy-D-glycero-D-talo-2-nonulosonsäure11 a umgewandelt werden. Die Verbindungen Methyl-5-acetamido-4-C-methylen-3,4,5-trideoxy--D-manno-2-nonulopyranosidonat (15) und Methyl-5-acetemido-4-C-methyl-3,4,5-tridoxy--D-glycero-D-talo-2-nonulopyranosidonat (16) wurden als Modellverbindungen für enzymatische Untersuchungen über peracetylierte Zwischenstufen hergestellt. Überraschenderweise zeigte nur die 4-C-Methylenverbindung15 eine starke kompetitive Hemmung gegenüber CMP-Sialat-Synthase.相似文献
14.
Oğuz Gürbulak 《Journal of Dispersion Science and Technology》2018,39(5):655-664
The influence of surface coverage to the structural properties of 4-n-octyl-4´-cyanobiphenyl (8CB) monolayer at the air/water interface was studied by full atomistic molecular dynamics simulations. These properties include density profiles, interface thickness, monolayer width, orientational order parameters, and atom-pair radial distribution functions. The calculated tilt angles of the cyanobiphenyl and alkyl parts are in fairly good agreement with the experiments. The simulation results exhibit the general trends in the previous experimental and simulation data. 相似文献
15.
《Solid State Sciences》2000,2(4):495-500
The polythermal diagram of the ternary system H2ONa2HPO4Na2SO4 has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow. 相似文献
16.
17.
Erich Kleinpeter Matthias Heydenreich Andreas Koch Torsten Linker 《Tetrahedron》2012,68(10):2363-2373
The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R–COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by 1H and 13C NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial/equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount. 相似文献
18.
Structural Chemistry - Charge transport and electronic properties of 4-nitro-4′-amino-azobenzene compounds with donor-acceptor backbone were examined at the molecular level. Optical... 相似文献
19.
L. M. Delitsin V. A. Sinelshchikov V. M. Batenin T. I. Borodina G. E. Valiano 《Doklady Chemistry》2015,465(2):303-307
In the course of segregation smelting of rare-earth and rare metal raw materials with a fluxing agent (NaF), two immiscible melts form, one of which is a silicate melt and the other is a phosphate–salt melt. The silicate melt is enriched with Fe2O3, Al2O3, SiO2, and Nb2O5, and the phosphate–salt melt is dominated by P2O5, TR2O3, Sc2O3, and Y2O3, and also with Ca, Sr, and Ba oxides. Chemical reactions between lanthanum orthophosphate and sodium fluoride in the LaPO4–NaF system were studied for developing a technology for processing the phosphate–salt (rare-earth metal) melt. It was found that a metathesis reaction gives double phosphate Na3La[PO4]2 and binary fluoride NaLaF4. The products of crystallization of melts in the LaPO4–NaF system decompose in weak mineral acids unlike those in conventional technology for processing monazite raw material. 相似文献
20.
1 INTRODUCTION Semiconductor silicon materials are vital for mi- croelectronic and information industry. Silicon has many advantages, for example, rich resource, out- standing quality and sophisticated processing tech- nology. So it has been widely used in semiconduc- tor industry. One of the key techniques of mo- dern microelectronic industry is epitaxial growth of single crystal thin film on single crystal silicon and its ba- cking materials. In the chemical vapour deposition of Si, g… 相似文献