A new set of spectroscopic constants of the 16O3 molecule (ωi, xij, yijk, γDD, iX, βijX,…), which determine vibrational dependence of band centres and rotational parameters, is derived from recent accurate analysis of high-resolution experimental ro-vibrational spectra through the theoretical approach based on second-order perturbation expansions in normal coordinates accounting for Darling–Dennison resonance interactions. These values are used to update empirical values of anharmonic coefficients (kijl, kijlm) of the potential function expansion in normal coordinates. Quadratic frr, fr, frr′, f as well as cubic frst and quartic frstl force constants in internal (bond lengths, bond angle) coordinates are also derived. A detailed discussion is devoted to the accuracy of parameter determination for each of four steps of calculations. It is emphasised that the conventional method based on the inversion of formulae of the perturbation theory gives the largest uncertainties at the last step of calculations: the determination of the anharmonic force field in internal coordinates. 相似文献
It has been known from the very beginning of the thermal analysis that the transport processes can significantly influence the thermoanalytical results. In this paper, three characteristic examples are given to show that this problem is more complex and arises more frequently than it is generally believed. The studied reactions are the carbon monoxide evolution from calcium oxalate, the thermal degradation of polytetrafluoroethylene, and the thermal decomposition of azodicarbonamide. TG and DSC experiments were carried out with sample masses varying between 0.05 and 8 mg. The necessity of the development of new kinetic models is concluded.
Zusammenfassung Seit den Anfängen der Thermoanalyse ist bekannt, dass Transportprozesse die thermoanalytischen Ergebnisse weitgehend beeinflussen können. Es werden hier drei Beispiele beschrieben, die zeigen, dass dieses Problem weitauf komplizierter ist und häufiger auftritt als allgemein angenommen wird. Die untersuchten Reaktionen sind die Kohlenmonoxidabspaltung aus Calziumoxalat, die thermische Zersetzung von Polytetrafluoräthylen und der thermische Zerfall von Azodicarbonamid. Die TG- und DSC- Untersuchungen wurden mit Probenmassen zwischen 0.05 und 8 mg durchgeführt. Es wird auf die Notwendigkeit der Entwicklung neuer kinetischer Modelle geschlossen.
Specific rate of methane conversion into C2-hydrocarbons and deep oxidation products in its interaction with O2 or N2O decreases with growing surface area of catalysts that are metal-like compounds of transition elements. This regularity is interpreted in terms of a heterogeneous-homogeneous mechanism.
The reaction of K[H6ReL2] with [RuHCl(CO)(PPh3)3−x {P(OPri}3)x](L2 = (PMePh2)2, dppe, (AsPh3)2, or (PPh3)2; x = 0, 1 or 2) leads to [L2(CO)HRe(μ-H)3RuH(PPh3)2−y{P(OPri)3}y] (x = 0 or 1, Y = 0; X = 2, Y = 1(L2 = PPh3)) in a first step. Under the reaction conditions most of these complexes react rapidly with the liberated phosphine giving [L2(CO)Re(μ-H)3Ru(PPh3)3−y- {P(OPri)3}y] (L2 = (PMePh2)2 or dppe, Y = 0; L2 = (PPh3)2, Y = 1) as the only iso complexes. The structure of [(PMePh2)2(CO)Re(μ-H)3Ru(PPh3)3] has been establishedby X-ray structure analysis. The complex [(PPh3)2(CO)Re(μ-H)3Ru(PPh3)2(P(OPri)3)] reacts with molecular hydrogen under pressure to generate [L2(CO)HRe(μ-H)3RuH(PPh3)(P(OPri)3) as the sole product. 相似文献
The reasons why the starting temperature of thermal decomposition cannot be utilized for the estimation of the thermal stabilities of co-ordination compounds are discussed. To establish the sequences of kinetic or thermodynamic stabilities of co-ordination compounds in thermal dissociation processes, it is indispensable to calculate the kinetic and thermodynamic parameters of the processes.
Zusammenfassung Der Grund, weshalb die Ausgangstemperatur der Thermolyse nicht zur Schätzung der Thermostabilität von Koordinationsverbindungen eingesetzt werden kann, wird erörtert. Um die Reihenfolge der kinetischen oder thermodynamischen Stabilität von Koordinationsverbindungen in thermischen Dissoziationsvorgängen zu ermitteln ist es unumgänglich die kinetischen und thermodynamischen Parameter der Vorgänge zu errechnen.
Résumé On discute les raisons pour lesquelles on ne peut pas se servir de la température du début de la décomposition thermique pour estimer la stabilité thermique des composés de coordination. Pour établir l'ordre de succession des stabilités des composés de coordination dans les processus de dissociation thermique, il est indispensable de calculer les paramètres cinétiques et thermodynamiques des phénomènes.
A study was made of the change in the properties of tin-antimony and bismuthmolybdenum oxide catalysts during the partial reduction of their surfaces with propylene and a propylene-ammonia mixture. Different characteristics of the interaction of ammonia with the surface of the catalysts studied were established.
The experiments have been performed by a microreactor pulse method at 623 K. The activity and selectivity of the catalysts, alumina/metal chloride and silica gel/metal chloride or oxide, have been found to depend on the donor-acceptor properties of their surfaces.
It is suggested that besides its traditional application to describe random nucleation, the first-order equation F1 can be used for the diffusion kinetics of gas-solid small particles reactions.
A new chromophore, C1 , based on a similar DπA‐structure as in the FTC ‐chromophore but with a hydroxyalkyl spacer perpendicular to the direction of the dipole moment was synthesized. Both chromophores and the CLD ‐chromophore were used to prepare high Tg nonlinear optical vinyl polymers. The influence of the position of the spacer on the DπA‐system on the NLO response of the resulting polymers was investigated.
The least distance of the closest approach, b*, of the Laidler-Landskroener equation has been evaluated by application of the Singh-Jha equation in case of acid catalyzed hydrolysis of benzyl formate in water-DMSO solvent system. The values obtained are quite reasonable.
Summary The Clemmensen reduction of dubinidinone (II) leads to the hydrogenolysis of the dihydrofuran ring with the predominant formation of -methoxy--methyl-,-dihydropyrano-2-quinolone.An explanation of the characteristics of the fragmentation of the products of the reduction of dubinidinone has been found.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 217–223, March–April, 1976. 相似文献
Some characteristics of the kinetic equation of dissolution are discussed, bearing in mind that in the course of the process, along with the concentration of the solution, the surface of the soluble substance is also changed. The opportunity for the appication of an exponential kinetic equation is pointed out. Methods are proposed for calculating the solubility and also for using the integral forms of the exponential equation. The meaning of the coefficient of proportionality is explained.
Using the CNDO method, a number of hydroxy-containing systems were calculated. The results are compared with IR spectroscopic data on the frequencies and acidity of surface OH groups and their dependence on the electronegativity of the atom to which the OH group is bonded.
Particle aggregation in polydisperse colloids is studied theoretically. It is assumed that the aggregation follows phase transition scenario with the formation of dense uniform colloidal phases. Bidisperse model corresponding to the system of relatively large and small particles is considered. Van der Waals attraction between large particles and the action of relevant entropy forces due to the presence of depleted layers of small particles are taken into account. The diagrams of equilibrium phase transitions of gas–liquid and gas–solid types occurring in the ensemble of large particles are constructed. The influence of size and concentration of small particles on the pattern and structure of phase diagrams is studied. It is shown that an increase in the concentration of small particles leads, on the one hand, to a rise of phase transition temperature and, on the other hand, to an increase in the threshold concentration of large particles. 相似文献
The electronic structure of the triphenylgallium molecule in the ground and electronically excited states has been calculated in the framework of the CNDO/S-CI method in sp and spd bases. The electron density in the AO's and atoms, the first ionization potential the energies and matrices of the changes in the electron density of the Sn and Tn states, the matrix elements of the spin-orbit coupling operator
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and
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, the intensities and directions of polarization of the Sn So and T2 Tn transitions, and the phosphorescence lifetimes have been calculated. The following spectroscopic parametrization has been proposed for the Ga atom in the sp and spd bases: 1/2(Is + as) = 10.075 eV, 1/2(Ip + Ap) = 4.265 eV, 1/2(Id + Ad)=0,
Gap
=5 eV,
Gad
=O,
Gasp
=–7 eV,
Gaspd
=–10 eV, and s,p,d=1.433. The influence of the d AO's on the shaping of the orbital nature of the S1 and T2 states has been analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 584–590, September–October, 1985. 相似文献
Both enantiomers of the antidepressant tranylcypromine, trans 2-phenyl-cyclopropy-lamine 1, were prepared in enantiomerically pure form by a chemoenzymatic approach starting from racemic (±)-(1RS, 2RS)-trans ethyl 2-phenyl-cyclopropane carboxylate (±)-3. 相似文献
The study describes the mathematical model, calculation and optimization of the technological scheme of the regeneration of the catalytic solution in the liquid-phase oxidation of hydrocarbons.
