共查询到20条相似文献,搜索用时 62 毫秒
1.
Summary Bifunctional methylenebis(diphenylphosphine oxide) (mdpo) on reaction with iron(III) perchlorate forms the complex, [Fe(mdpo)3](ClO4)3 · H2O. This has been characterized through elemental analysis, i.r., far-i.r., u.v. and visible spectroscopy and by x-ray diffraction, magnetic moment, molar conductance and e.s.r. data. The e.s.r. spectrum consists of five lines with transitions from: ¦–5/2¦–3/2¦–3/2¦–1/2, ¦–1/2¦+1/2¦+1/2¦+3/2 and ¦+3/2¦+5/2 centred at a g-value of 2.00. On the basis of these studies, a chelated octahedral structure has been assigned to the cation, [Fe(mdpo)3]3+. 相似文献
2.
A. V. Chernova G. M. Doroshkina R. R. Shagidullin B. E. Abolonin 《Russian Chemical Bulletin》1990,39(4):846-848
Short-wavelength nSe * and long-wavelength nSe * bands are observed in the UV spectra of saturated trialkylarsine selenides in the near-UV region. The nx * band in going from arsine selenides to arsine sulfide and then to arsine oxides is shifted hypsochromically, as in the corresponding phosphorus compounds. The nx * band is only slightly sensitive to the chalcogen. Saturated trialkylarsines, in contrast to alkylphosphines, absorb in the near UV region (the nAs * band is at 208 nm).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 940–942, April, 1990. 相似文献
3.
The effects of protonation on the charge distributions of pyridine and cytosine are investigated with the help of the Iterative Extended Hückel technique. The polarization of the -electrons is then included explicitly in a Pariser-Parr-Pople computation of the -
* transition energies of the pyridinium and cytosinium ions.
This work was supported by grant n GM-12229 of the U.S. Public Health Service (National Institute of General Medical Sciences). 相似文献
Zusammenfassung Mit Hilfe der IEH-Methode wird die Auswirkung der Protonierung auf die Ladungsverteilung bei Pyridin und Cytosin untersucht. Die Polarisierung der -Elektronen wird dann in eine PPP-Rechnung der - *-übergangsenergie beim Pyridinium- und Cytosiniumion übernommen.
Résumé On étudie, à l'aide de la méthode de Hückel étendue iterative, les effets de la protonation sur la répartition des électrons dans les molécules de pyridine et de cytosine. On introduit ensuite explicitement la polarisation des électrons dans le calcul des énergies de transition - * des ions pyridinium et cytosinium par la méthode de Pariser, Parr et Pople.
This work was supported by grant n GM-12229 of the U.S. Public Health Service (National Institute of General Medical Sciences). 相似文献
4.
Remi Chauvin 《Journal of mathematical chemistry》1996,19(2):147-174
Within the prospect of quantifying the geometrical dissimilarity of molecular models on the basis of a thermodynamical formalism, the algebra of stereogenic pairing equilibria is reviewed and applied to molecular geometry: developing Rassat's proposition, an interaction energy of two figures F and F is taken as proportional tod
H
Emphasis>/2
(F, F), whered
H denotes the Hausdorff distance. IfG is a group of rotations in E
n
the geometrical version of the general equation (E) of the chemical algebra defines a distance extensionD
p(F,F) ofd
H(F,F), which is independent of the orientations of F and F, and where the coefficientp is interpreted as the reciprocal of a temperature-like parameter:p 1/T. At K (p = ), no formal entropy contributes to the definition of the uniform distanceD
. At K (p = 0), the discrimination between homo- and hetero-pairing of figures by the harmonic distance Do is averaged over orientation states. Temperature-dependent chirality measuresc
p are derived fromD
p, andc
is analogous to Mislow's chirality measure. If T and oT are normalized enantiomorphic triangles with coincident centroids inE
2,c
p(T) =D
p (T, T) is calculated forp = 0 andp = , and discussed for 0 <p < . Finally, the Hausdorff interaction model is putatively related to energy profiles versus dihedral angle inmeso- anddl-molecules. 相似文献
5.
The kinetics of many solid state reactions can best be explained in terms of an order of reaction; this is particularly true in the case of polymer degradation. The methods currently available for the determination ofn andk, from isothermal data, are either limited in the range of which can be used or are difference-difference techniques where the data must of necessity be highly accurate. This paper presents a review of these methods and introduces a new approach by whichn andk can be obtained directly, giving results which are unique and objective in that they provide a best fit to the experimental data.
The calculations presented in this paper were performed on an ICL 4130 computer using the program SOLITER. This program was written in ALGOL 60. 相似文献
Zusammenfassung Die Kinetik vieler Reaktionen in fester Phase kann am besten an Hand einer Reaktions-Ordnung erklärt werden; dies besteht besonders bei dem Abbau von Polymeren. Die für die Bestimmung vonn undk aus isothermen Daten zur Verfügung stehenden Methoden sind entweder auf den verwendbaren Bereich von beschränkt oder sind Differenz-Differenz-Methoden, bei welchen es äußerst genauer Angaben bedarf. Die vorliegende Veröffentlichung gibt eine übersicht dieser Methoden und führt eine neue Annäherung ein, durch welchen undk unmittelbar erhalten werden können. Diese Methode ergibt einzigartige und zielgerechte Ergebnisse, indem diese sich den Versuchsdaten am besten anpassen.
Résumé Pour de nombreuses réactions dans l'état solide l'ordre de réaction constitue un très bon moyen pour exprimer leur cinétique; c'est le cas, en particulier, de la dégradation des polymères. Les différentes méthodes dont on dispose pour déterminern et k à partir des données isothermes sont limitées à l'intervalle d'utilisation de ou opèrent par différences successives ce qui nécessite des données très précises. L'article présente une revue de ces méthodes et introduit une nouvelle approche oùn etk peuvent Être obtenus directement, en donnant des résultats uniques et objectifs qui assurent un meilleur accord avec les données expérimentales.
; . , n ,k . , « — », . , n k. .
The calculations presented in this paper were performed on an ICL 4130 computer using the program SOLITER. This program was written in ALGOL 60. 相似文献
6.
Egorochkin A. N. Skobeleva S. E. Bogoradovsky E. T. Zubova T. P. 《Russian Chemical Bulletin》1994,43(6):976-982
The resonance donor effect of the , conjugation of R3M and R3MCH2 (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R3MC=CX and R3MCH2CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial + charge on the triple bond enhances , conjugation; a partial – charge on the triple bond has practically no effect on the resonance properties of R3M substituents, whereas the , conjugation of R3MCH2 substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372). 相似文献
7.
M. S. Prasada Rao A. Rama Mohan Rao P. Vani 《Reaction Kinetics and Catalysis Letters》1992,48(2):519-528
The kinetics and mechanism of reduction of thallium(III) by hydrogen peroxide has been studied in 1.0 mol dm–3 perchloric acid medium. The reaction is first order with respect to thallium(III) and second order with respect to hydrogen peroxide. A negative hydrogen ion and chloride ion catalysis is observed. Bromide ion is found to catalyze the reaction in low concentration. There is no effect of ionic strength on the rate of the reaction. A plausible mechanistic pathway for the reaction is suggested which leads to the following rate law: Rate=–d[T1(III)]/dt=kK[T1(III)][H2O2]2/[H+] where K is the formation constant of the complex between thallium(III) and hydrogen peroxide and k is the rate constant of the reaction between that complex and hydrogen peroxide. The computed values of Ea and S# are 44.8±6.5 kJ mol–1 and –107.8±22.2 JK–1 mol–1, respectively.
(III) - - . - (III) . - - . . -- . , - :=–[T1(III)]/dt=kK[T1(III)][H2O2]2/[H+], - (III) - . EA S# 44,8±6,5 / –107,8±22,1 /·, .相似文献
8.
A. A. Medvinskii Yu. M. Baikov N. N. Bulgakov G. G. Saveliev E. K. Shalkova 《Reaction Kinetics and Catalysis Letters》1981,17(3-4):413-417
The mechanism of hydrogen isotope exchange in aqueous alkaline solutions (AAS) of D2 has been studied using Interacting Bonds Method (IBM) data obtained for hydrogen interaction with the molecular ion H3O
2
–
. Models for the activated and metastable intermediate complexes are described.
- D2 (). () H3O 2 – . .相似文献
9.
Klaus Helfrich 《Theoretical chemistry accounts》1984,65(5-6):449-454
If x denotes an exact solution of the quantum mechanical two centre Coulomb problem, we optimize a normalized LCAO approximation by making the overlap S = (x¦) a maximum. In this context we study how a weight factor (r
a
r
b
)–1 in the definition of the inner product changes the approximation and the expectation value of electronic energy. Finally we compare the lower bound given by the Eckart criterion with the exact overlap. Results are reported for H
2
+
states 1sg and 2pu.Dedicated to Professor Hermann Hartmann on occasion of his 70th birthday on May 4th, 1984 相似文献
10.
M. I. Krivopustov J. Adam V. Bradnova R. Brandt V. S. Butsev P. I. Golubev V. G. Kalinnikov J. Karachuk B. A. Kulakov E.-J. Langrock G. Modolo M. Ochs R. Odoj A. N. Premyshev V. S. Pronskich Th. Schmidt V. I. Stegailov J. S. Wan V. M. Zupko-Sitnikov 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):267-270
First experiments on the transmutation of long-lived129I and237Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:129I(n,)130I and237Np(n,)238Np. The isotopes130I (T
1/2-12.36 h) and238Np (T
1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (129I(n,))=(10±2)b and (237Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna. 相似文献
11.
Zusammenfassung Es wird ein isothermer Schnitt im System Nb2O5 -Li2O-Sc2O3 untersucht. Dabei wurde die neue Verbindung Li0.5Sc0.5Nb2O6 gefunden. Die Röntgenreflexionsaufnahmen ergaben unter Annahme eines orthorhombischen Gitters die Parameter a=1433.6/2/ pm, b=572.96/6/ pm und c=505.76/4/ pm.Bei 1453 K wurde der LiNbO3-Homogenitätsbereich bestimmt, der sich vom binären System Li2O-Nb2O5 bis zu 5 mol% Sc2O3 im Dreikomponentensystem erstreckt. Im Homogenitätsbereich wurde die Variation der Gitterkonstanten gemessen. Das Volumen der Elementarzelle nimmt mit steigendem Sc2O3-Gehalt zu.
An isothermal section was investigated in the system Nb2O5-Li2O-Sc2O3. The new compound Li0.5Sc0.5Nb2O6 was found The x-ray reflection pattern could be indexed with the assumption of an orthorhombic lattice with the parameters of a=1433.6(2) pm, b=572.96(6) pm, c=505.76(4) pm.The LiNbO3-homogeneity range was determined at 1453 K. It extends from the binary Li2O-Nb2O5 to 5 mole-% Sc2O3 in the ternary system. The variation of the lattice constants of LiNbO3 was measured in the homogeneity range. The volume of the unit cell increases with increasing content of Sc2C3.
Nb2O5-Li2O-Sc2O3, Li0,5 Sc0,5Nb2O6. , $ = 1433,6/2/ , =572,96/6/ =505,76/4/ . 1453 LiNbO3, $ Li2O-Nb25 $ 5 %. $ . .相似文献
12.
The first vertical ionization potentials (I) of halides HalX (Hal = Cl, Br, I; X is an inorganic or organic substituent) are linearly related to the inductive (I), resonance (R
+), and polarizability () constants of the substituents X (I = a + bI + cR
+ + d). As the atomic number of the Hal element in the Hal·+X radical cations increases, the inductive interaction is strengthened while the polarizability interaction is weakened. Conjugation remains virtually independent of the Hal atom. The resonance R
+-constants of the MX3 (M = Si, Ge, Sn, Pb) substituents bound to the Hal·+ radical cation centers were first calculated. 相似文献
13.
Ya. S. Yakhyaev S. N. Khadzhiev T. M. Gairbekov S. E. Spiridonov 《Reaction Kinetics and Catalysis Letters》1986,30(2):263-268
The effect of hydrothermal treatment of decationized superhigh-silica zeolite on the mechanism of n-hexane conversion has been studied. It has been established that thermosteam modification sharply decreases the cracking activity and increases the selectivity to aromatization reactions. Zeolite acidity markedly decreases, but its crystal structure does not become amorphous.
-. . .相似文献
14.
A. V. Gribanov L. A. Shibaev A. I. Koltsov R. E. Teeiaer Yu. N. Sazanov N. G. Stepanov E. P. Lippmaa T. Székely 《Journal of Thermal Analysis and Calorimetry》1987,32(3):815-823
The mechanisms of thermal degradation processes in polypromellitimide films were investigated by mass-spectrometric thermal analysis and high-resolution NMR spectroscopy in the solid state. Both the structures of the solid residues of pyrolysis products of the PM polyimide and the process of carbonization proper up to 1200° were studied. It was established that the breaking of the Car-O-Car bond in the diamine moiety is not the primary act of degradation of the molecular structure of the polymer, as might be expected on the basis of the value of the bond energy. The process of intermolecular crosslinking following polymer degradation under high-temperature conditions is completed by the formation of a complex nitrogen-containing heterocyclic structure.
Zusammenfassung Der Mechanismus der in Polypyromellitfilmen ablaufenden thermischen Zersetzungsprozesse wurde durch massenspektrometrische thermische Analyse und hochauflösende Festkörper-NMR-Spektroskopie untersucht. Sowohl die Struktur des festen Rückstandes des Pyrolyseproduktes des PM-polyamids als auch der Prozeß der Verkokung bis 1200 °C wurden Untersucht. Es wurde festgestellt, daß das Aufbrechen der Bindung C ar ,-O-C ar im Diaminteil nicht der primäre Schritt der Zersetzun der molekularen Struktur des Polymers ist, wie nach dem Wert der Bindungsenergie zu erwarten wäre. Der auf die Hochtemperatur-Polymerzersetzung folgende Prozeß der intermolekularen Vernetzung endet mit der Bildung einer komplexen stickstoffhaltigen heterozyklischen Struktur.
- (MTA) (MP BPTT) , 1200 °C. . , C ap -C ap , , .相似文献
15.
Egorochkin A. N. Voronkov M. G. Skobeleva S. E. Zderenova O. V. 《Russian Chemical Bulletin》2001,50(1):35-42
The first vertical ionization potentials (I) of phosphorus compounds P(Xi)3, OP(Xi)3, SP(Xi)3, (4-XC6H4)3P, and PCX are related to the inductive, resonance, and polarizability parameters of inorganic, organic, and organometallic substituents X by dependences of the type I = I
H + aI + bR
+ + c, where I
H is the I value for X = H. The I values are also affected by hyperconjugation. The ratio of the contributions of the resonance (bR
+) and polarizability (c) effects to the I value is determined by the degree of delocalization of the unpaired electron and the positive charge in the radical cations formed upon ionization of neutral molecules. The R
+ resonance parameters of organosilicon, organogermanium, and organotin substituents bound to the P
·+ radical cation center were calculated for the first time. 相似文献
16.
The ability of various approximate coupled cluster (CC) methods to provide accurate first-order one-electron properties calculated as expectation values is theoretically analysed and computationally examined for BH and CO. For actual calculations the infinite number of terms of the expectation value expansion (O=¦exp (T
+)O exp (T)¦c) was truncated so that T
1
T
2, T
3, and (1/2) T
2T2 clusters were retained on both sides of O. The role of individual clusters is carefully discussed. Inclusion of T
1, is unavoidable, but if triples are essential in the energy evaluation, they may play an even more important role in the property expansion, as shown in the case of CO. It is shown that the CC wave function, which is exact to second order, effectively satisfies the Hellmann-Feynman theorem. 相似文献
17.
D. Andrae U. Häußermann M. Dolg H. Stoll H. Preuß 《Theoretical chemistry accounts》1991,78(4):247-266
Summary Recently published nonrelativistic and quasirelativistic energy-adjustedab initio pseudopotentials representing the M(Z–28)+ cores of the second row transition metal atoms and the M(Z–60)+ cores of the third row transition metal atoms have been tested in SCF, CI(SD) and CEPA1 calculations of the spectroscopic constants (R
e
,D
e
, and
e
) of the ground states of the neutral and singly charged silver and gold dimers, and in state averaged CASSCF and multi-reference CI(SD) calculations of the spectroscopic constants (R
e
,D
e
,
e
,
e
, /R). Comparison is made with experimental and reliable theoretical data where available; in the case of the hydrides, additional calculations with pseudopotentials published by other groups have been made for comparison. 相似文献
18.
O. A. Kizas V. V. Krivykh V. V. Vorontsov A. A. Koridze 《Russian Chemical Bulletin》1993,42(6):1102-1103
Protonation of triosmium clusters Os3(-H)(CO)9(3-,2-CC-R) (R=CMe2OH, C(Me)=CH2) affords a cationic complex containing a six-electron propargyl ligand which has been detected for the first time.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1144–1145, June, 1993. 相似文献
19.
I. M. Issa Dr. K. A. Idriss M. M. Seleim 《Monatshefte für Chemie / Chemical Monthly》1977,108(6):1461-1469
The reaction of 1,4-(2-sulpho-4-methylanilino)anthraquinone (quinizarin green,QG) and its non-sulphonated derivative (NSQG) with Ce(III), Th(IV), and U(VI) was investigated. Spectrophotometric and conductometric studies were carried out to investigate the stoichiometry of the complexes formed. The studies revealed the formation of 11 and 12 (ML) complexes. The apparent stability constants of the different complexes were determined. The structure of the ligand in the solid chelates was studied by IR spectrophotometry which showed that the chelate formation takes place through the oxygen of the C=O group and the -imino nitrogen.
Mit 6 Abbildungen 相似文献
Mit 6 Abbildungen 相似文献
20.
C. Gascó M. P. Antón A. Espinosa A. Aragón A. Alvárez N. Navarro E. García-Toraño 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):81-86
Plutonium isotopic ratios have been calculated in soils contaminated by the Palomares accident which occurred in 1966 (Almería, Southeastem Spain). Contrasted techniques have been used to determine the radionuclide activities:238Pu and238+240Pu were analysed by -spectrometry prior purification on anion-exchange resins, the ratio239Pu/240Pu was estimated by -spectra deconvolution and241Pu was directly measured by liquid scintillation counting and indirectly through quantification of in-grown241Am from aged plutonium discs. The mean activity ratios238Pu/239Pu,239Pu/240Pu,241Pu/239Pu, backdated to 1966, were 0.027±0.002 (1), 4.5±0.2 (1) and 8.2±0.8 (1), respectively, characterizing the accident of Palomares as the source term of the measured plutonium. 相似文献