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1.
The proton magnetic resonance spectra of alkyl-substituted stannanes RnSnH4-n have been studied. The hydride proton resonance appears always lower field with respect to stannane itself and the downfield shift increases with n. A theoretical interpretation of this trend in terms of the magnetic anisotropy of Sn-C bond is temptatively given.  相似文献   

2.
The 19F and 1H high resolution NMR spectra of the (p-fluorophenyl)chlorostannanes (FC6H4)nSnCl4-n have been observed at room temperature. The NMR parameters have been compared with the molecular structures and are in accord with the view that p{π}-d{π} interaction occurs between the phenyl ring π-orbital and the empty 4d tin orbital when n > 2.  相似文献   

3.
Résumé La phénothiazine et son radical sont probablement pliées le long de l'axe passant par les deux hétéroatomes centraux. Des calculs sont effectués par la méthode des orbitales moléculaires sur la modification des caractéristiques électroniques de la phénothiazine en fonction du pliage. On montre, que les densités de spin calculées pour les différentes configurations spatiales possibles du radical phénothiazinique permettent, par comparaison avec les densités expérimentales, de choisir la configuration la plus probable. C'est la configuration pliée dans laquelle le proton attaché à l'azote se trouve placé entre les deux cycles latéraux. L'étude des potentiels d'oxydation polarographique montre qu'au contraire dans les dérivés 10-substitués de la phénothiazine, le substituant aliphatique trop volumineux est placé hors des cycles latéraux.
Phenothiazine and its free radical are probably folded along the axis passing through the two central heteroatoms. Calculations are carried out by the molecular orbital method on the modification of the electronic characteristics of the phenothiazine ring as a result of folding. It is shown, in particular, that the spin densities calculated for the different possible geometrical configurations of the phenothiazine free radical permit, by comparison with experimental spin densities, to deduce which configuration is the most probable. In the present case, this is the folded configuration in which the proton attached to the nitrogen atom is placed between the two lateral rings. The energy of the highest filled molecular orbital is also a sensitive function of the geometrical configuration of the molecule. The study of the polarographic oxidation potential of substituted phenothiazines shows that, in contrast to the parent molecule, in the N-alkyl substituted derivatives the voluminous alkyl substituent is probably pushed out to an external position with respect to the lateral rings.

Zusammenfassung Phenothiazin und sein Radikal sind wahrscheinlich längs der N-S-Verbindungslinie geknickt. Wir berechneten nach der MO-Methode die Änderungen der elektronischen Eigenschaften des Moleküls mit dem Knickwinkel. Der Vergleich der für die verschiedenen denkbaren Konfigurationen des Radikals berechneten Spindichten mit Meßwerten erlaubt, eine von ihnen als am wahrscheinlichsten auszuwählen. Es ist die geknickte Form, in der das H-Atom am Stickstoff zwischen den aromatischen Ringen liegt. Die Untersuchung der polarographischen Oxydationspotentiale zeigt dagegen, daß in den N-alkyl-substituierten Phenothiazinderivaten die aliphatische Gruppe von den Seiten-Ringen wegsteht.


Ce travail a bénéficié de la subvention CY-3073 du Public Health Service des Etats-Unis (National Cancer Institute).  相似文献   

4.
The ethylene and tetrafluoroethylene polymerization in a “cold plasma” leads to polymers with considerable deficiencies of hydrogen or fluorine atoms. With electronic spin resonance, the various kinds of radicals trapped in the macromolecular structure have been detected and in some cases identified and determined. The mechanisms could be partly explained in thermodynamic terms. Irradiation of the corresponding commercial polymers gives some information about degradation processes in the plasma.  相似文献   

5.
《Comptes Rendus Chimie》2002,5(6-7):493-505
The characterisation of the surface electrical properties of membrane materials is critical for understanding and predicting the filtration performances of membranes. In this paper, four simple experimental methods – streaming potential, electro-osmosis, pore conductivity and membrane potential –, allowing the characterisation of the charge state of membrane pore walls are presented. The four experimental parameters provide information about the sign of the electrical net charge. Examples illustrating the influence of the pH, electrolyte concentration and nature on the four experimental parameters are given. The zeta potential can be then deduced from these measurements by means of a model.  相似文献   

6.
The electronic structure of typical organomagnesium compounds is calculated by the SCF molecular orbital method, using a set of gaussian atomic orbitals. The most stable conformation of MgX2 compounds is found to be linear for all the basic orbitals. A comparaison is made for the energy and structure of MgF, MgCl and MgC bonds; the analysis of the electronic density curves suggests a pronounced ionic character for those bonds.  相似文献   

7.
The chemical shifts of acetylenic proton and of methyl protons attached to a triple bond in mono- and poly-acetylenic derivatives of groups IVb, Vb and VIb elements, have been carried out at 60 MHz, in carbon tetrachloride or deuterochloroform at infinite dilution.The heteroatom-proton coupling through the acetylenic system has been observed for phosphorus, silicon, tin and lead derivatives.The results are discussed on the basis of electronic effects.  相似文献   

8.
Divalent manganese ion Mn2+ is paramagnetic and has played an important role in the history of Nuclear Magnetic Resonance and in Magnetic Resonance imaging (MRI). In another way it can be taken up by neurons as an analog to Ca2+. So, particular interest in the use of Mn2+ stems from its potential as an MRI contrast for cerebral studies on normal rodent and on experimental models of diseases. This work presents the three major classes of applications of the Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) for brain experimental studies. The utility of MEMRI method for following development of the brain in physiological and pathological states is particularly pointed out.  相似文献   

9.
A complete assignment is given for the i.r. and Raman spectra of pyrimidine in the liquid state. It depends upon comparison with the spectra of some pyrimidino-chloride complexes of iridium (III) in the 3500-350 cm−1 range. The 17a (A2) fundamentals have been identified and new frequencies are proposed for the 4, 7b, 10b, 18b modes. Previous interpretations are discussed in the light of the new data.  相似文献   

10.
11.
The authors have studied the potentiometric curves obtained during the neutralization, in dilute alcoholic media, of acid solutions containing 2-phenyl-8-quinolinol and metallic cations, with sodium hydroxide. By thermogravimetric analysis the number of water molecules and regions of stability for hydrates and anhydrous compounds were also established.Moreover these results were compared with those previously obtained for oxinates and methyl-2 oxinates.  相似文献   

12.
FT-IR Characterization of superficial and acidic properties of phosphated zirconia. The nature of phosphate species formed by impregnation of zirconia by (NH4)2HPO4 followed by decomposition at 400°C was studied by IR spectroscopy. These species present hydroxyl groups characterized by a ν(OH) band at 3666 cm−1 due to the P-OH stretching vibration. The structure of phosphate species was examined using H218O isotopic exchange. Acid-base properties of phosphated zirconia was investigated by CO2, pyridine and acetonitrile adsorption followed by FT-IR spectroscopy. The introduction of phosphated species, creates Brønsted acid sites on zirconia. A slight increase in Lewis acidity and a strong decrease in basicity is also detected.  相似文献   

13.
《European Polymer Journal》1985,21(10):903-908
One can characterize the large-scale displacements of a macromolecule by the time required for the chain to renew completely its conformation. These displacements are displayed by changing the topological orientation of the condensation reactions. This effect is produced by putting the medium through a sound wave or an alternating electric field that is in resonance with the Brownian motion of the macromolecule. The physical contact between the chains is enhanced and the intermolecular reactions are more frequent than the intramolecular reactions. The application of a sound wave or an electric field of a characteristic frequency on the elastomers during chemical crosslinking produces a noticeable change in the crosslinking density.  相似文献   

14.
Résumé La théorie L.C.A.O. améliorée est appliquée à l'étude des éthers vinylique et divinylique. La grande différence d'électronégativité entre les orbitales atomiques entrant dans la liaison entre l'oxygène et le carbone nous a conduits à introduire la déformation réciproque de ces orbitales. Les énergies calculées pour la première transition N V, 6,5 et 6,3 eV, sont en excellent accord avec l'expérience.
The improved L.C.A.O. theory is applied to the vinyl and divinyl ethers. The large differences of electronegativity between the atomic orbitals which enter the-bond between oxygen and carbon led us to the introduction of the mutual deformation of these orbitals. The calculated energies for the first N V transition, 6,5 and 6,3 eV are in excellent agreement with experiment.

Zusammenfassung Die verbesserte L.C.A.O.-Theorie wird auf Vinyl- und Divinyläther angewandt. Die große Elektronegativitätsdifferenz zwischen den an der-Bindung zwischen Sauerstoff und Kohlenstoff beteiligten Atomzuständen hat uns veranlaßt, die gegenseitige Deformation dieser Zustände einzuführen. Die für die erste N V-Elektronenbande berechneten Energien, 6,5 und 6,3 eV, stimmen ausgezeichnet mit der Erfahrung überein.
  相似文献   

15.
The i.r. and laser Raman spectra of pyrazine and some pyrazine-complexes of iridium (III) have been investigated in the frequency range of the internal vibrations of the diazine. Samples were examined in the gaseous, liquid, or solid states or in solution. A complete and coherent vibrational assignment is deduced for pyrazine and previous interpretations are discussed in the light of the new data.  相似文献   

16.
The improved LCAO method is used to study the electronic structure of phenol, phenoxide ion, and phenol perturbed by a hydrogen bond. The calculated transition energies are in good agreement with experiment. A new method is proposed to determine the differences of reactivity between the different atoms of the aromatic ring. The results are satisfactory.  相似文献   

17.
Viruses of the Nepovirus group have a bipartite genome. In the case of the tomato black ring (TBRV) subgroup, the two RNA of MW 1.5 × 106 and 2.5 × 106 daltons are respectively diistributed in two nucleoproteins B and M. Some severe TBRV strains have an additional small RNA of 0.5 × 106 daltons called RNA3 encapsidated in two special nucleoproteins M′ and T′.TBRV-S strain containing such an RNA3 was specially investigated here. Elimination of RNA3 from this strain is difficult, and requires polyacrylamide gel electrophoresis under denaturing conditions (urea 8 M, 65°C). Elimination of RNA3 from the strain does not result in any modification of symptoms. RNA3 has all the characteristics of a satellite RNA which does not multiply by itself. Its multiplication needs the presence of the two RNA of the S strain: it cannot be introduced in another strain naturally free of a small satellite RNA or in 2 pseudorecombinant strains containing respectively one of the major RNA of the S strain. Its only role in the infection process, is to modify the relative proportions of the virus RNA.  相似文献   

18.
The Raman spectra of three 2-butynes: CH3CCCH3, CH3CCCD3 and CD3CCCD3, and four 2-pentynes: C2H5CCCH3, C2H5CCCD3, C2D5CCCH3 and C2D5CCCD3 in the liquid state have been measured. From a comparative analysis of the spectra, together with previous work on 1-butynes, a vibrational assignment is derived. The analysis of the 2000–2400 cm−1 range allowed us to precise the Fermi resonance interaction between ν(CC) and 2νa(CC
CC). An assignment of the several bands shown by the Raman spectrum of 3-hexyne in this range has been proposed.  相似文献   

19.
Photoionization studies on solid solutions of various aromatic molecules S have shown —besides the S+ optical absorption spectra—those of SH+ (in the case of anthracene in boric acid) and of S2+ (for tetramethyl-paraphenylene-diamine (TMPD) in glassy ethanol).From thermoluminescence experiments on photoionized durene in methylcyclohexane, it may be estimated that approximately one-half of all electrons having an initial kinetic energy of about 1 eV travel at least 60 Å before stabilization.Electron spin resonance analyses have indicated that for HBO2 glass, practically all the solute photoelectrons are trapped by the acidic protons of the matrix. The recorded thermoluminescence would thus be a chemiluminescence sensitized by excited molecular hydrogen. For the system TMPD-ethanol, the thermoluminescence emission is very weak, and most of the negative species formed would be S or (and) solvent radical-anions.  相似文献   

20.
The authors prepared phenyloxin by three different methods. They obtained a product whose melting point was 59° C and then another form melting at 72° C. Ultraviolet absorption spectra were determined in cyclohexan and in alcohol-watermixtures; from these determiaations, the solubilities of phenyloxin in water and in alcohol-water mixtures of different concentrations were obtained. If ultraviolet absorption spectra are plotted for different pH values (from 1.1 to 13.7) several isobestic points are noted.  相似文献   

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