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1.
V. M. Bzhezovskii N. N. Il’chenko M. B. Chura L. G. Gorb L. M. Yagupol’skii 《Russian Journal of General Chemistry》2005,75(1):86-93
The potential functions of internal rotation around the C
-S bond in the C6H5S(O)CH3 and C6H5S(O)CF3 molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C
-S-C
bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C
-S bond, corrected for the zero-point vibration energy, are 21.29 [C6H5S(O)CH3] and 28.98 [C6H5S(O)CF3] kJ mol−1. The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C
SO), 106.3 (C
SO) in C6H5S(O)CH3; 93.5 (CSC), 108.2 (C
SO), 105.2 (C
SO) in C6H5S(O)CF3. The bond lengths are as follows (Å): 1.520 (S=O), 1.804 (C
-S), 1.810 (C
-S) in C6H5S(O)CH3; 1.507 (S=O), 1.799 (C
-S), 1.870 (C
-S) in C6H5S(O)CF3. According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent σ bond (S→O) and an almost ionic bond. An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)→σ*(C
-S) and n(O)→σ*(C
-S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 96–104.Original Russian Text Copyright © 2005 by Bzhezovskii, Il’chenko, Chura, Gorb, Yagupol’skii. 相似文献
2.
G. A. Oweimreen 《Journal of solution chemistry》1982,11(2):105-118
Infinite dilution solute activity coefficients
o
2
, partial molar excess enthalpies
and entropies
, and partial molar enthalpies (
) and entropies (
) of solution, obtained using gas-liquid chromatography (GLC), are reported for thirty nonmesomorphic solutes in the nematic and isotropic phases of p-n-hexyl-p-cyanobiphenyl (6CB). The solutes studied include normal and branched alkanes, alkenes and hexadienes (with some cis and trans isomers), and benzene. The results corroborate earlier studies on other members of the p-n-alkyl-p-cyanobiphenyl homologous series of liquid crystals. The results demonstrate the effect that solute structure (size, shape, flexibility, polarizability and polarity) has on the solution process. Thermodynamic data for the cis and trans isomers of 2-pentene and 2-hexene are examined. A method for the simultaneous examination of the effects of both solute and solvent structures on the solution process is suggested. 相似文献
3.
We derive two expansions of the Randles–Sevcik function
: an asymptotic expansion of
for x and its Taylor expansion at any x
0
. These expansions are accompanied by error bounds for the remainder at any order of the approximation. 相似文献
4.
Group contributions to
in seven solvents and to
in three solvents have been tabulated. The variation of
group parameters is discussed in terms of the solvent compressibility coefficient, T. The scaled particle theory (SPT) is used to calculate cavity contributions to
and C
p2
o
. Interaction contributions are obtained from the cavity terms and
and
values estimated through the additivity schemes.
values are more sensitive to solute-solvent interactions than
in water and less sensitive in methanol. The SPT results for heat capacities support the concept of structural promotion by hydrophobic solutes in water. 相似文献
5.
The apparent molal volumes (v) and compressibilities (K) of CaSO4 solutions have been determined at 25°C from precise density and sound-speed measurements. The large deviations of the values of v and K from the limiting law and various additivity estimates for the free ions (Ca2+, SO
4
2–
) have been used to estimate the partial molal volume (
) and compressibility (
) for the formation of the CaSO
4
0
ion pair. Values of
= 25 ± 3 cm3-mole–1 and
= (54±21)×10–4 cm3-mole–1-bar–1 were found. Since these values are larger than the value for the formation of MgSO
4
0
, the results indicate that more inner-sphere ion pairs are formed when SO
4
2–
complexes with Ca2+ than with Mg2+. Using a simple model for ion-water interactions, the percent of inner-sphere or contact ion pairs in CaSO4 solutions is estimated to be 36 to 37%. 相似文献
6.
B. Szczepaniak J. Goralski J. Grams W. Maniukiewicz T. Paryjczak 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(12):1992-1996
A series of ZrO2-TiO2 mixed oxides with different weight ratios (5, 20, and 30% ZrO2) were prepared by wet impregnation of TiO2-P25 Degussa with certain amounts of ZrO(NO3)2·6H2O (Fluka) dissolved in deionised water. The samples were characterized by the XRD,
,
,
, and BET methods. An increase in ZrO2 content shifted the phase transition temperature (anatase into rutile) toward higher temperatures. X-ray diffraction using
an Anton Paar XRK900 reactor chamber indicated that, in the case of samples containing ZrO2, an additional diffraction peak appeared after cooling down to 25°C. This peak could be attributed to a polymorph of TiO2 such as in the single crystal of anatase or hexagonal form of TiO2 which appears in the presence of ZrO2. Generally, the preparation of dioxide systems can modify the properties of pure compounds or generate new catalytic sites
as a result of strong interaction between ZrO2 and TiO2 oxides. The binary systems exhibit advantages like strong acidity, extended specific surface area, and high thermal stability
in comparison with TiO2.
The article is published in the original. 相似文献
7.
In this brief work we express the cycle index of the molecular point groups as a function of a limited number of initial geometrical parameters. Such parameters are the number
of elements composing the domain D of sites of substitutions in the molecule belonging to the point group G, and the numbers
of sites of D lying on the symmetry elements
for G. 相似文献
8.
Zusammenfassung Bei niedrigen Umsätzen und einer Polymerisationstemperatur von 50°C erhaltene Polyvinylacetate sind unverzweigt; das gleiche gilt für Polyvinylchoracetate. Bei diesen wurde die bei höheren Umsätzen auftretende Verzweigung durch Verseifung und Acetylierung der Polymeren sowie durch Messung von []-,
und
Werten an den Polymeren bestimmt. Eine Selbstverzweigung der wachsenden Kette konnte nicht gefunden werden. *** DIRECT SUPPORT *** A3615144 00012
Chain branching in vinyl chloroacetate and vinyl acetate polymerization
Polymerization of vinyl acetate and vinyl chloroacetate to low conversions at 50°C gave unbranced polymers. The branching of polyvinyl chloroacetates at higher conversions was determined by hydrolysis and acetylation of the polymers and by measuring [], and . No self-branching of the growing chains could be found.相似文献
9.
O. V. Frank-Kamenetskaya I. V. Rozhdestvenskaya L. A. Yanulova 《Journal of Structural Chemistry》2002,43(1):89-100
The crystal structures of three minerals (arsenosulvanite, V,As-germanite, and colusite) of the general crystal chemical formula
(As, Ge, Sn, Sb, V)6S32, where CuM, VM are cations at interstitial positions, 0.2 x 2.0, 2.7 y 0, (space group
, a = 10.527; 10.600; 10.653 ; R = 0.066; 0.046; 0.033) have been determined using single-crystal X-ray diffraction data. The minerals are the two structural modifications of the compound with the ideal formula V2Cu24As6S32; they differ from each other in the occupancy of the interstitial position 2a. In colusite, this position is occupied by the V5+ cations; in arsenosulvanite and V,As-germanite, by Cu2+. A characteristic feature of the structures is the presence of octahedral [
S4]Cu6 (
= V, Cu) complexes not directly interacting with each other and lying inside the Laves polyhedra. In the structures of arsenosulvanite and V,As-germanite, a sulvanite framework consisting of interpenetrating Laves polyhedra
T3S4 (
= V, Cu; T = Cu, As, Ge) has been found. The sulvanite framework is statistically distributed over the sphalerite matrix. The variable composition of the minerals is due to heterovalent isomorphism in the sphalerite position 6c. Charge disbalance arising from substitution of the pentavalent arsenic cations by cations of lower valence is compensated by the appearance of additional Cu2+ cations. The nonstoichiometry of the compositions is explained by the presence of vacancies in the interstitial and sphalerite positions. 相似文献
10.
The promotion of the branched-chain decomposition of nitrogen trichloride by molecular hydrogen additives at room temperature and 20 torr manifests itself in a decrease in the induction period and the acceleration of reactant consumption with an increase in the hydrogen concentration in the NCl3+ H2+ He mixtures. The emission spectrum of the H2+ NCl3flame contains the intense bands of NCl
(b
1+– X
3–, = 1 – 0, = 0 – 1, and = 0 – 0, where is the vibrational quantum number) and the bands of a hydrogen-free compound. The latter bands can be assigned to electronically excited NCl
2radicals formed in the H + NCl3reaction. The calculations restrict the number of elementary reactions favoring promotion. The promotion effect in the system studied should be due to the side reaction of linear branching. The occurrence of the H + NCl3reaction via two pathways (NHCl
+ 2Cl and NCl
2+ HCl) ensures the qualitative agreement between the experimental data and calculation. 相似文献
11.
《Reaction Kinetics and Catalysis Letters》1984,24(1-2):157-160
The effect of the amount of diethylamine and triethylamine on the degree of poisoning of a hydrogenation catalyst 10% Pt on silica gel was examined. The dependence of the selectivity of competitive catalytic hydrogenation of 2-methyl-3-butene-2-ol and 1-hexene in methanol and cyclohexane on the degree of poisoning was investigated.
(10% Pt ), 2--3--2- 1- .相似文献
12.
Analytic expressions relating the concentration of a light-sensitive component and the intensity of exposure UV light to the sample thickness and exposure time of light-sensitive materials with the restricted mobility of reactants were found. The processes of image formation were considered, which involve the following reversible photochemical reactions: (1) both steps are photochemical,
; (2) a thermal reaction acts as a reversible step,
; and (3) both thermal and photochemical reactions are reversible steps,
.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 218–222.Original Russian Text Copyright © 2005 by Zelentsov, Simdyanov. 相似文献
13.
István Szalkai 《Journal of mathematical chemistry》1999,25(1):31-46
The phases of multicomponent systems (mixtures, states, etc.) containing the compounds
are
, where
and
. For
(quaternary or higher dimensional systems), the displaying methods and visual investigations in the
dimensional Euclidean space
are tangentially or not at all described in the literature. In this paper we first develop the theoretical (both mathematical and computational) background in any dimension in
. We focus not only on the important points, lines, surfaces of these systems, and computing method of the states of some processes in such systems, but also on the approximating methods of the above mentioned lines and surfaces, and, finally, on the question which is the region where a state (a point) falls into. Using the above results a computer program for PC's was created for evaluating and displaying the approximated surfaces. This program is described in I. Szalkai, SALT3DIM.exe – A program for handling 4 component mixtures, Preprint No. 047, University of Veszprém (1996), and the computing results are planned to be published in a forthcoming paper (I. Szalkai, Handling multicomponent systems in
. II: Computational results, J. Chem. Inf. Comput. Sci., submitted). 相似文献
14.
Carbonate stability constants for yttrium and all rare earth elements have been determined at 25°C and 0.70 molal ionic strength by solvent exchange and inductively coupled plasma–mass spectrometry (ICP–MS). Measured stability constants for the formation of
and
from M3+ are in good agreement with previous direct measurements, which involved the use of radio-chemical techniques and trivalent ions of Y, Ce, Eu, Gd, Tb, and Yb. Direct ICP–MS measurements of
and
formation constants are also in general agreement with modeled stability constants for the metals La, Pr, Nd, Sm, Dy, Ho, Er, Tm, and Lu, based on linear-free energy relationship (LFER). The experimental procedures developed in this work can be used for assessing the complexation behavior of other geochemically important ligands such as phosphate, sulfate, and fluoride. 相似文献
15.
For cyclopentane used as a model hydrocarbon, solubility in water and aqueous solutions of various salts (chlorides, bromides, iodides, rhodanides, alkali metal acetates and sulfates, and calcium and zinc chlorides) at 20±1°C has been determined. Variations of the increment of the methylene group (
) induced by salt additions to water, are calculated. When the salt is added to the solution, the increment
increases drastically irrespective of the nature of the ions, thus stabilizing the structure of the solution. The increase, however, depends significantly on the nature of the salt, which is explained by different degrees of structuring of the aqueous solution caused by the ions of the salts. 相似文献
16.
Linear ethylene oxide-dimethylsiloxane PEO-PDMS-PEO triblock copolymers have been synthesized by hydrosilation of ,-dihydropoly(dimethylsiloxane)
) and -methyl--propargylpoly(ethylene oxide)
. Studies by optical microscopy, complementary small-angle x-ray scattering (SAXS), and differential scanning calorimetry (DSC) have shown that the copolymers mixed with water are characterized by lyotropic liquid crystalline phases according to composition and temperature. The binary phase diagrams with varying copolymer composition are reported. 相似文献
17.
Luminescence Behavior of Polynuclear Alkynylcopper(I) Phosphines 总被引:1,自引:0,他引:1
A series of soluble trinuclear and tetranuclear copper(I) complexes containing 3-l acetylides
, and
have been synthesized and shown to exhibit rich photoluminescent behavior at room temperature. The electrochemistry of the trinuclear Cu(I) acetylide complexes and the excited-state redox properties of
have been investigated. The X-ray crystal structures of
and
have been determined. 相似文献
18.
V. R. S. Rao G. Erdtmann H. Petri 《Journal of Radioanalytical and Nuclear Chemistry》1989,135(4):257-264
The extent of exchange of bromine-82 with bromamine-T in strong acid medium is low due to the formation of
at lower acid concentrations and bromine at higher acidities.
formation occurs over a narrow acid concentration range and is less stable than
. 相似文献
19.
Iron ions are shown to play a special role among transition metal ions in the oxidation of sulfite by oxygen. The thermodynamically favorable formation of chain carriers S
: FeOH2++ HSO3
– Fe2++ H2O +
, H
r
298
0 –250 kJ/mol accompanied by the regeneration of the active Fe(III) form in the reactions of Fe(II) with
and HSO5
–provides the efficient catalytic mechanism for sulfite consumption even at [Fe]0 10–8mol/l. Any aqueous solution contains iron ions in this amounts. Thus, the noncatalytic oxidation of sulfite is in fact the catalytic reaction involving unavoidable microadmixtures of iron ions. Other transition metal ions (Mn2+, Co2+, etc.) can only enhance the catalytic effect of iron admixture. 相似文献
20.
T. E. Kokina L. A. Glinskaya R. F. Klevtsova S. V. Larionov 《Journal of Structural Chemistry》2002,43(2):312-321
The reaction of Ni{(i-C4H9)2PS2}2 with imidazole and 3,5-dimethylpyrazole in ethanol gave paramagnetic (ef = 3.02 and 3.11 BM) mixed-ligand complex compounds [Ni(Im)2{(i-C4H9)2PS2}2] (I) and [Ni(Pyr){(i-C4H9)2PS2}2] (II). Single crystals were grown and the crystal structures of I and II were determined from X-ray diffraction data (CAD-4 diffractometer, Mo
radiation, 1483
, R = 0.0344 for I and 2630
, R = 0.0486 for II). The crystals are monoclinic with cell dimensions a = 12.845(2), b = 10.250(1), c = 13.431(1) , = 115.89(1)°, V = 1591(1) 3, Z = 2, d
calc = 1.281 g/cm3, space group
(for I); a = 11.152(3), b = 12.483(2), c = 23.389(4) , = 100.78(1)°, V = 3199(2) 3, Z = 4, d
calc = 1.191 g/cm3, space group
(for II). The structures consist of discrete monomer molecules. The coordination polyhedron of the Ni atom is a compressed octahedron NiN2S4 (in I) and a tetragonal pyramid NiNS4 (in II) formed by four S atoms of the two cyclic bidentate ligands i-Bu2
and the N atoms of two monodentate ligands (Im molecules in trans-positions) or the N atom of the monodentate Pyr ligand in complexes I and II, respectively. The character of interaction between molecules I and II and molecular packing modes are considered. The electronic spectra of the complexes are consistent with the symmetry of chromophores found from X-ray data. 相似文献