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1.
Using the ab initio LCAO—SCF—MO method and the 6–31G extended basis set, the CN radical and its possible dimers (NCCN, CNNC or CNCN) have been studied in terms of nuclear equilibrium geometries, normal modes of vibration, IR spectrum and thermodynamic properties. The results show that quantum chemical calculations enable these parameters to be obtained with adequate accuracy. Working properly, one can build a local potential energy surface on which to perform a harmonic vibrational analysis. Hence all the required information to apply the principles of statistical thermodynamical analysis is available. 相似文献
2.
《Materials Chemistry》1982,7(1):35-42
Electrical measurements of corrosion scales growing on copper and nickel in SO2O2 atmospheres show a different behaviour for both metals. For copper, the electrical conductivity indicates that Cu2S is formed in pure SO2 and Cu2O in SO2O2 mixtures (ratio PSO2/PO2 = 105). In the case of nickel, the high conductivity of product scales in atmospheres containing pure SO2 or SO2O2 is consistent with an interconnected Ni3S2 phase in NiO. In all cases the corrosion scales have a positive Seebeck coefficient. 相似文献
3.
Resumé Les lois de mélange classiques valables en général pour de très faibles fractions volumiques en matière dispersée sont étendues aux fortes concentrations par la méthode de Bruggeman. On indique les relations obtenues pour la distribution aléatoire d'ellipsoïdes au sein d'un milieu continu. Le cas des ellipsoïdes anisotropes est considéré ainsi que celui des systèmes multidispersés á plusieurs constituants.En illustration on a étudié par analyse numérique le cas des ellipsoïdes isotropes de révolution dispersés dans un milieu isolant en mettant l'accent sur l'influence du rapporta/b des demi-axes.
Blending laws derived for very small volume fractions of dispersed medium are extended to high concentrations, using Bruggeman method. Derivation is made in the case of a random distribution of ellipsoids dispersed in a continuous medium. The case of non isotropic ellipsoids and the case of multicomponent systems are also considered.As an example, a numerical analysis is made in the case of isotropic ellipsoids of revolution dispersed in an insulating medium; particularly, the effect of the semi-axis ratioa/b is pointed out.相似文献
4.
The results of the conformational study of a benzothiazolinic dimethinmérocyanine (open form) are described. Variations of electron π energy (Pariser-Parr-Pople method) and of non bonding energy are considered.All possible conformations have been investigated and the results of computations give evidence for a twisted structure, confirming a previous study taking account of σ and π electrons (Extended Huckel method). 相似文献
5.
P. Claudy J.M. Letoffe S. Vilminot W. Granier Z. Al Ozaibi L. Cot 《Journal of fluorine chemistry》1981,18(3):203-212
Fluorides and some mixed halogen fluorides of tin(II) have been studied by X-ray diffraction, differential scanning calorimetry, and conductimetry. From a consideration of structural properties a relationship has been established between the co-ordination sphere, ionic mobility and entropy of fusion. 相似文献
6.
《Annales de Chimie Science des Materiaux》2002,27(1):19-32
Influence of pH on the chemical and structural properties of the oxide films formed on 316L stainless steel, alloy 600 and alloy 690 in high temperature aqueous environments. The oxide films formed on 316L stainless steel, alloy 600 and alloy 690 at 320°C in high temperature aqueous environments of different pH have been examined by glow discharge optical spectroscopy, scanning electron microscopy, atomic force microscopy and capacitance measurements. The analytical study reveals that the films formed at pH 5 are mainly composed of chromium oxides. When the pH increases the chromium concentration decreases and those of the other two elements (Ni and Fe) tend to increase. The films formed at pH 5 on 316L stainless steel and alloy 600 are thick and powder-like. The film formed at the same pH on alloy 690 is thin and is composed of a compact protective inner layer and a less-compact outer layer formed by crystals of mixed iron-nickel-chromium oxides. The morphological appearance of the thick films and that of the thin films is very different. However, equivalent morphologies can be observed for the relatively thin duplex films formed at pH8 and pH9.5 on the 316L stainless steel and nickel-base alloys. The evolution of the chemical composition of the films is accompanied by important changes from the point of view of their semiconductivity. 相似文献
7.
Thermal decomposition of lorazepam begins by lose of a water mole between two groups NH-OH and occurs at different temperatures depending on the formes of polymorphs. Melting temperature of a form can be determined only if it is below that of decomposition.The thermoanalytical and spectral study of lorazepam commercial drugs (a) and (b) recrystallisation product at 20°C in benzine (c), in carbon tetrachlorid (d), in acetonitrile (e) were carried out.Thermal behaviour, RX diffraction, IR spectroscopy allow us to identify polymorph (a, b, c) and two solvates (d and e). The solvates stoechiometry (d and e) has been determined by thermogravimetry (3-2) d, (2-1) e, and confirmed by magnetic nuclear resonance for (e).
Nous exprimons nos vifs remerciements à Madame Eliane Toreilles, Directeur de recherche au CNRS (Laboratoire de Chimie Organiques UA 458 CNRS, Ecole Nationale Supérieure de Chimie de Montpellier) pour sa collaboration personnelle en spectroscopie. 相似文献
8.
Résumé Les auteurs rappellent et comparent quatre méthodes de minéralisation des composés organiques en vue d'y doser le soufre: ce sont la méthode de combustion oxhydrique, la combustion dans l'oxygène, soit en tube droit vide, soit en fiole du type «Schöniger» et la minéralisation réductrice en tube scellé par le potassium. Ils les associent aux méthodes de titrage des ions SO4
2– ou S2–.Leur étude leur permet de sélectionner parmi les méthodes décrites la minéralisation réductrice par le potassium associée au titrage iodométrique des ions S2– comme la plus universelle et la plus sûre d'entre elles.Résumé Four methods of mineralization of organic compounds are recalled and compared with respect to determining sulfur in them; they are the oxyhydrogen combustion method, combustion in oxygen, in an empty tube, or in a flask of the Schöniger type, and the reductive mineralization in a sealed tube by potassium. They are combined with the titration methods for the SO4
2– or S2– ions. This study has enabled the authors to select the reductive method of mineralization by means of potassium followed by the iodometric titration of S2– ions as the most general and most reliable among the various procedures.
A M. le ProfesseurJureek, D. Sc. à l'occasion de son 60ème anniversaire. 相似文献
Zusammenfassung Die Verfasser berichten vergleichend über vier Methoden zur Mineralisierung organischer Verbindungen, deren Schwefelgehalt bestimmt werden soll, und zwar die Verbrennung in der Knallgasflamme, im Sauerstoffstrom im leeren Rohr, im Schönigerkolben und die reduktive Zerstörung mit Kalium im verschlossenen Röhrchen. Diese Methoden wurden mit der maßanalytischen Bestimmung des Sulfats bzw. Sulfids kombiniert. Daraus ergab sich, daß die Reduktion mit Kalium und die nachfolgende jodometrische Bestimmung des Sulfids am allgemeinsten anwendbar und am sichersten ist.
A M. le ProfesseurJureek, D. Sc. à l'occasion de son 60ème anniversaire. 相似文献
9.
The Gibbs thermodynamic variables which we have determined for thirteen brass alloys (Cu, Zn) are in good accord with the literature. The experimental conditions were as close as possible to those of sublimation in static vacuum. The application of the test of the third law in β-brass shows that our free enthalphy measurements are in agreement with the measurements of specific heat by Moser. The primary solid solution α copper of the binary brasses shows quasi-regular behaviour over the whole composition range. Our measurements seem to indicate the existence of a β′/(α + γ) eutectoïd at a temperature less than 100°C. The high degree of order of the γ phase is seen in the large negative values of excess entropy. 相似文献
10.
Progressive addition of sodium sulphide to a sulphur solution in dimethylsulphoxide results in the formation of polysulphide ions, identical to those obtained by electrochemical reduction of sulphur in the same solvent. Conversely, electrochemical oxidation of sulphide leads to the formation of sulphur-sulphur bonds, and cyclooctasulphur S8 is finally obtained. 相似文献
11.
C. Duprez-Quesnoit 《International journal of quantum chemistry》1977,11(3):381-391
A quantum calculation of the optical activity and gyrotropic birefringence is used in a molecular crystal to deduce symmetry properties. A study of the variation of the components of these tensors, when a change of origin occurs, is used to account for the formula for the electric excitation proposed by Landau and Lifchitz. It is shown that the results obtained are valid in the case of crystals with nonlocalized electrons. 相似文献
12.
The syntheses of [4]rotane and polycyclopropylspiranic derivatives are reported. One route involves the formation of cyclopropane rings from C4-acyloins; a second route uses the dimerisation of bicyclopropylidene. Spectroscopic data do not point to any particular electronic interactions between cyclopropane rings in these compounds. 相似文献
13.
《Journal of fluorine chemistry》1986,31(1):1-7
Lithium pentafluorotellurate (IV) LiTeF5 has been prepared by different methods:
- •slow evaporation of a 1/1 mixture of lithium fluoride and tellurium dioxide or tellurium tetrachloride in anhydrous hydrogen fluoride,
- •heating a 1/1 mixture of lithium fluoride and tellurium tetrafluoride. LiTeF5 is orthorhombic
14.
Some diazapolyoxamacrocycles have been polycondensed with different difunctional compounds to give polymers and gels. Their synthesis and their complexing properties towards alkali metals and calcium cations are reported. 相似文献
15.
A. Elfakir M. Quarton B. Monnaye R. Bouaziz 《Journal of Thermal Analysis and Calorimetry》1989,35(5):1561-1569
A partial study of the Li2O-P2O5 and ZnO-P2O5 binary diagrams led to establishment of the polymorphism of Li3PO4 and of Zn3(PO4)2. Three crystalline forms were found for Li3PO4, differring from one another only on the cation distribution at the tetrahedral sites of the almost hexagonal compact arrangement of the anions. Li3PO4 differs from the isostructural compounds Li3VO4 and Li3AsO4 in its irreversible transformation at low temperature. Zn3(PO4)2 is dimorphic, with a reversible transformation. It displays a slight non-stoichiometry through a ZnO deficiency.
Zusammenfassung Aufgrund einer teilweisen Untersuchung der binären Diagramme von Li2O-P2O5 und ZnO-P2O5 konnte der Polymorphismus der Verbindungen Li3PO4 und Zn3(PO4)2 näher beschrieben werden. Für Lithiumorthophosphat wurden drei kristalline Formen gefunden. Sie unterscheiden sich voneinander nur in der Kationenverteilung in den tetraedrischen Gebilden der fast hexagonal kompakten Anordnung der Anionen. Li3PO4 unterscheidet sich von den isostrukturellen Verbindungen Li3VO4 und Li3AsO4 durch seinen irreversiblen Übergang bei niedriger Temperatur. Zinkorthophosphat ist dimorph und zeigt eine reversiblen Umwandlung. Es weist wegen ZnO-Mangels eine geringe Abweichung von der stöchiometrischen Zusammensetzung auf.
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16.
The reaction of cyclopentadienylthallium with chlorophosphines yields cyclopentadienyl phosphines 1, 4, 6 and 8. Some of their derivatives (oxides, sulfides and methyl iodides) have been prepared. Their NMR shows that phosphorus is mainly bonded to the first position of the cyclopentadiene nucleus. Starting with diphenyl (1,3-cyclopentadienyl) phosphine sulfide 2 we have also studied the Diels-Alder reactivity, the bromination and the metalation of the cyclopentadienyl group. This last reaction allows the synthesis of some new phosphorus substituted fulvenes 16, 17 and 18. We have also prepared the new cyclopentadienylid 19 from the dimeric methyliodide 11. 相似文献
17.
A series of N-dimethylgallylazoles have been prepared by treatment of azoles (imidazoles, benzimidazoles, pyrazoles, s-triazole and benzotriazole) with trimethylgallium.The structure (monomeric, dimeric, polymeric) of the resulting compounds depends on the position of the nitrogen atoms in the azole moiety. In the case of pyrazolyl derivatives, the NMR study in acetone or acetonitrile shows the existence of an equilibrium between the monomeric and dimeric forms. 相似文献
18.
We have already studied some physicochemical properties of aliphatic polythioamides and the contribution of the thioamide group to some of them. We now report the thermal behaviour of these condensation polymers and determine the functional group participation to molar melt and glass transition functions. These results allow us to compare polyamides, polyesters and polythioamides. We have also studied some polythioamides containing ether-linkages. Thermal degradation has been studied by thermogravimetric analysis. 相似文献
19.
Marianne Chevrier Olivier Bensaude Jean Guillerez Jacques-Emile Dubois 《Tetrahedron letters》1980,21(35):3359-3362
In contrast to what observed with mono hydroxy-pyridines and -pyrimidines the lactim-lactam equilibrium of uracils is not found to be markedly influenced by solvent polarity. 相似文献
20.
Selenium and tellurium isotopes formed by thermal neutron irradiation have longer half-life than the copper isotope. The non-destructive
analysis fails even after the complete decay of copper because of the other radioisotope present. The radioisotopes were separated
by ion exchange chromatography on Dowex 1X8 (200–400 mesh) and “Pertitanic” resins in order to obtain a highly sensitive analysis.
The limits of detection of 5 ppb for tellurium and 0.5 ppb for selenium were obtained.
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