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1.
Isothermal compressibilities T and isobaric thermal expansion coefficients p have been determined for mixtures of ethylbenzene+n-nonane, +n-decane, and +n-dodecane at 25 and 45°C in the whole range of composition. The excess functions
and
have been obtained at each measured mole fraction. The first one
is zero for ethylbenzene +n-nonane, positive for ethylbenzene +n-decane, and +n-dodecane and increases with chain length n of the n-alkane. The
function is positive for the three studied systems and nearly constant with n. Both mixing functions increase slightly with temperature. From this measurement and supplementary literature data of molar heat capacities at constant pressure C
P
, the isentropic compressibilities S, the molar heat capacities at constant volume C
V
and the corresponding mixing functions have been calculated at 25°C. Furthermore, the pressure dependence of excess enthalpy H
B
,
at zero pressure and at 25°C has been obtained from our experimental results of
and experimental literature values for excess volume V
E
. 相似文献
2.
G. I. Golodets 《Theoretical and Experimental Chemistry》1967,1(6):506-510
A correlation has been found between the ease of reduction of oxides,
(where
is the reciprocal of the absolute temperature at which reduction by hydrogen commences), and their catalytic activity in relation to the oxidation of hydrogen, propylene, methane and the dehydrogenation of isopropyl alcohol. In the oxidation of hydrogen, propylene, and methane, the catalytic activity in the series of oxides investigated increases with increase in
; in the cases of the oxidation of ammonia and naphthalene, the dependence of the catalytic activity on
is represented by an inverted-V curve. 相似文献
3.
Previously developed additivity schemes for nonelectrolytes have been used to estimate
and
for tetraalkyl and tetraphenyl methanes in methanol and water. Corrections have been applied to the thermodynamic values of these model compounds to account for a variation in size of the central atom, and these were used to ascertain the effect of charge on
and
of alkyl and phenyl quaternary ions having N, P and B as central atoms. Investigations of R4NBr, (R=methyl to heptyl) salts show that the charge effect on
and
of R4N+ ions is large and relatively independent of ion size suggesting that the solvent molecules penetrate the ions. The ability to estimate
and
of the quaternary ions in the bromide salt solutions has made it possible to make ionic assignments with some confidence;
(Br–) has been evaluated as 19.7±2 and 30.2±7 cm3-mol–1 and
(Br–) as –83±7 and –68±30 J-K–1-mol–1 in methanol and water, respectively. The use of organic ions for making ionic assignments of
and
is critically examined and comparisons with other assignments are made. The scaled particle theory is employed to divide the heat capacities of electrolytes into cavity and interaction contributions. 相似文献
4.
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
5.
The difference between the partial molal entropies of ferrocene and ferricinium
has been determined in nine solvents from the temperature dependence of the formal potential of the ferricinium-ferrocene redox couple using a nonisothermal electrochemical cell arrangement in order to probe possible structural reasons for the limitations of the ferrocene assumption for estimating the transfer thermodynamics of single ions between different solvents. In contrast to the uniformly small positive values of
predicted by the Born model, the experimental quantities varied widely from small or even negative values in hydrogen-bonded solvents (–5 to 3 e.u.) to substantially larger values (11–14 e.u.) in dipolar aprotic media. These variations appear to arise chiefly from additional solvent ordering in the vicinity of the ferricinium cation compared to the ferrocene molecule which is enhanced in the aprotic solvents. The variations in
between water and a number of nonaqueous solvents provide a predominate contribution to the differences between the free energies of single ion transfer calculated using the ferrocene and alternative extrathermodynamic assumptions. 相似文献
6.
Summary A general definition of reaction graphs is presented. For a pair of isomeric molecular graphs
and
, related by a chemical transformation
, the reaction graph
is determined using a maximal common subgraph defined for vertex mapping
. A binary operation defined for graphs constructed over the same vertex set enables us to decompose the reaction graph
into the sum of prototype reaction graphs. A decomposition of an overall reaction graph can be advantageously used for the construction of a reaction network. An oriented path in this network beginning at
and ending at
corresponds to a breakdown of the transformation
into a sequence of intermediates. 相似文献
7.
Anna Rita Campanelli Fabio Ramondo Aldo Domenicano István Hargittai 《Structural chemistry》1999,10(1):29-40
The molecular structure and conformation of p-bis(trimethylsilyl)benzene have been investigated by gas-phase electron diffraction, ab initio MO calculations at the HF/6-31G*, MP2(f.c.)/6-31G*, and B3LYP/6-31G* levels, and MM3 molecular mechanics calculations. The calculations indicate the syn- and anti-coplanar conformations, with two
bonds in the plane of the benzene ring, to be energy minima. The perpendicular conformations, with two
bonds in a plane orthogonal to the ring plane, are transition states. The two coplanar conformers have nearly the same energy with a low interconversion barrier, 0.3–0.5 kJ mol–1. The calculated lengths of the
and
bonds differ by only a few thousandths of an angstrom, in agreement with electron diffraction results from molecules containing either
or
bonds. The geometrical distortion of the benzene ring in p-bis(trimethylsilyl)-benzene may be described by superimposing independent distortions from each of the two SiMe3 groups. The electron diffraction intensities from a previous study (Rozsondai, B.; Zelei, B.; Hargittai, I. J. Mol. Struct.
1982, 95, 187) have been reanalyzed, imposing constraints from the theoretical calculations, and using a model based on a 1:1 mixture of the two coplanar conformers. The effective torsion angles of the SiMe3 groups may indicate nearly free rotation. Important geometrical parameters from the present electron diffraction analysis are
, and
. While the mean bond lengths are virtually the same from the previous and present analyses, the new ipso angle is in better agreement with the MO calculations [HF, 116.9° MP2(f.c.), 117.1° B3LYP, 116.9°]. 相似文献
8.
M. Baudler und P. Stuhlmann 《Fresenius' Journal of Analytical Chemistry》1963,195(3):186-195
Zusammenfassung Die papierchromatographische Trennung von Mono- und Diphosphorsäuren (einschließlich der Triphosphorsäure
) in Gemischen wird durch die Verwendung eines Laufmittels mit Methanol als organischer Komponente wesentlich verbessert. Mit einem wäßrig-ammoniakalischen Methanol-Dioxan-haltigen Fließmittel gelingt nach der absteigenden Arbeitsweise die Trennung sämtlicher in Betracht kommender Säuren, während nach der aufsteigenden Methode nur die
und
-Säure nicht befriedigend trennbar sind.Daneben werden einige Erfahrungen zur Arbeitsmethodik, vor allem über die Papiersorte, die Entwicklung und die Nachweisbarkeitsgrenze, mitgeteilt.Auszug aus der Diplomarbeit F. Stuhlmann, Köln 1962Der Deutschen Forschungsgemeinschaft und dem Fonds der chemischen Industrie danken wir für die Unterstützung dieser Arbeit. 相似文献
9.
Summary The oxidation of H2O2 by [W(CN)8]3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law,
, strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k
s, given by
, involves the formation of [W(CN)8· H2O2]3–, [W(CN)8· H2O2·W(CN)8]6– and [W(CN)8· HO]3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)8·HO]3– (k
a) and its conjugate base [W(CN)8·O]4– (k
b). At 25 °C, I = 0.20 m (NaCl), the rate constant
with H
a
=40±6kJmol–1 and S
a
=–151±22JK–1mol–1; the rate constant
with H
b
=36±1kJmol–1 and S
b
=–136±2JK–1mol–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)8·HO]3–, K
5
=(5.9±1.7)×10–10
m, with
and
is the first acid dissociation constant of H2O2. The second pathway, with rate constant, k
f, involves the formation of [W(CN)8· HO2]4– and is followed by a formal two-electron redox process with [W(CN)8]3–. The pH-dependent rate constant, k
f, is given by
. The rate constant k
7
=23±6m
–1
s
–1 with
and
at 25°C, I = 0.20 m (NaCl). 相似文献
10.
The reaction of ethyleneimine with sulfenyl chlorides RSCl at –10 C in the presence of a hydrogen chloride acceptor (triethylamine) leads to the formation of N-organylthioaziridines
. Compounds with R=n-C5H11, C6H5, o-O2NC6H4 and C6H6CH2 have been obtained by this method.
and
. have been synthesized analogously.The properties and IR spectra of these compounds have been studied. The action of methyl iodide on N-phenylthioaziridine leads to disproportionation of the molecule with the formation of diphenyl disulfide, -iodoethyltrimethylammonium iodide, and free iodine.For communication VI, see [I]. 相似文献
11.
Excess molar volumes
for binary mixtures of acetonitrile + dichloromethane, acetonitrile + trichloromethane, and acetonitrile + tetracloromethane at 25°C have been used to calculate partial molar volumes
, excess partial molar volumes
, and apparent molar volumes
of each component as a function of composition. The V
m
Evalues are negative over the entire composition range for the systems studied. The applicability of the Prigogine–Flory–Patterson theory was explored. The agreement between theoretical and experimental results is satisfactory for the systems with dichloromethane and tetrachloromethane. For the unsymmetrical behavior of the system with trichloromethane, however, the agreement is poor. 相似文献
12.
Excess molar volumes
and viscosities (η) have been measured as a function of composition for binary liquid mixtures of 1-propanol, C3H7OH, with diethylene glycol diethyl ether(bis(2- ethoxyethyl)ether), C2H5(OC2H4)2OC2H5, and diethylene glycol dibutyl ether (bis(2-butoxyethyl)ether), C4H9(OC2H4)2OC4H9, at 288.15, 298.15, and 308.15 K and at atmospheric pressure. The excess volume results included the following mixing quantities
at all range of concentrations and at equimolar concentrations: α, volume expansivity;
, and
at 298.15 K. The obtained results were then compared with the calculated values by using the Flory theory of liquid mixtures.
The theory predicts the α values rather well, while the calculated values of
and
show variation with alkyl chain length of the polyether. The results are discussed in terms of order or disorder creation.
From the viscosity data, deviations in viscosity (Δη) have been calculated. These values are negative over the entire range
of composition. The results for
, and Δη are discussed in terms of interaction between components 相似文献
13.
Sarada Gopinathan Shilpa S. Deshpande Changaramponnath Gopinathan 《Transition Metal Chemistry》1993,18(6):585-587
Summary Hexacoordinated ruthenium(II) alkenyl complexes of the type Ru(CO)(CR=CHPh)(
)(PPh3)2 have been prepared from coordinately unsaturated -vinyl complexes [Ru(CO)Cl(CR=CHPh)(PPh3)2] (R = H or Ph) and the sodio-derivative of the
containing heterocyclic ligands [
= 3,4-substituted 1,2,4-triazole-5-thione and 5-alkylthio-1,3,4-thiadiazole-2-thione] in a CH2Cl2/MeOH mixture at ambient temperature. The complexes were characterized by their elemental analysis, i.r., 1H and 31P n.m.r. spectra. An octahedral structure with transphosphorus ligands has been assigned on the basis of the spectral data. 相似文献
14.
Yu. Yu. Samitov N. K. Tazeeva N. A. Chadaeva G. Kh. Kamai 《Chemistry of Heterocyclic Compounds》1973,9(4):422-427
The configuration and conformations often 2-, 4-, and 5-substituted 1,3,2-dioxaarsenanes were studied from their PMR spectra. Inversion of the shielding constants of protons in the 4, 6, and 5 positions and of methyl groups in the 5 position was established, and the axial orientation of the As-Cl and As-OR bonds, the equatorial orientation of the 4-CH3 group, and the chair conformation of the six-membered heteroring were proved. The anisotropies of the diamagnetic susceptibility were estimated for the first time:
and
(dipole approximation);
and
(nondipole approximation). The cyclic torsion angle (= 58°) as found for 2-chloro-1,3,2-dioxaarsenane by the R-factor method. Conclusions regardiwng the conformation of the ring and substituents were confirmed by a study of the specific effect of an aromatic solvent on the position of the resonance lines.Communication I from the series Investigation of the Stereochemistry of Organic Arsenic Compounds by NMR Spectroscopy.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 457–463, April, 1973. 相似文献
15.
N. N. Zatsepina I. F. Tupitsyn A. I. Belyashova A. A. Kane N. S. Kolodina G. N. Sudakova 《Chemistry of Heterocyclic Compounds》1977,13(8):894-903
The IR and PMR spectra of an extensive series of methyl derivatives of aromatic and heteroaromatic compounds were investigated. With a few exceptions, the experimental data on the chemical shifts of the protons
and the intensity of the band of the symmetrical stretching vibration [(ACH)1/2] for five- and six-membered heterorings can be united in a single reaction series with polysubstituted toluenes within the framework of an additive scheme. The (ACH)1/2 values correlate satisfactorily with the calculated (by the CNDO/2 method) total charges on the carbon and hydrogen atoms of the methyl group. In contrast to the intensities of the IR bands, linear relationships between the chemical shifts and the charges on the hydrogen atoms are observed only within the limits of particular reaction series. The lack of a unified relationship was interpreted as being the result of the effect of the ring current, the contribution of which to the
value depends on the nature of the heteroatom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1110–1119, August, 1977. 相似文献
16.
By analyzing the topological structures of the three types of icosahedral fullerenes: (1)
, (2)
and (3)
k,\;h,k = 1,2,...} \right)$$
" align="middle" border="0">
, we have obtained theoretically the 13C NMR spectra with natural abundance for 13C of all the icosahedral (Ih and I) fullerenes. 相似文献
17.
Polosukhin A. I. Bondarev O. G. Lyubimov S. E. Shiryaev A. A. Petrovskii P. V. Lysenko K. A. Gavrilov K. N. 《Russian Journal of Coordination Chemistry》2001,27(8):591-597
Phosphorylation of (S)-prolinol with P(NEt2)3was used to synthesize aminophosphite (2R,5S)-
, which was reacted with the corresponding amino alcohols to afford (2S,5R)-
(Va) and (2S,5R)-
(Vb). Reaction of Vawith [Rh(CO)2Cl]2(P/Rh = 1) yields the mononuclear chelate [Rh(CO)(P^N)Cl] (VIIa), while the analogous reaction with Vbresults in a mixture of products with cis- and trans-orientation of the coordinated phosphorus and nitrogen atoms. Spectral characteristics of the products of coordination of ligands Vaand Vbwere compared with those for the binuclear reference complex [Rh(CO)(L)Cl]2(VIII), where L is P-monodentate ligand (2S,5R)-
(VI). The ligands and complexes were studied by IR, NMR, 31P and 13C spectroscopy, mass spectrometry, and elemental analysis methods. X-ray diffraction analysis of crystals VIIIwas performed. 相似文献
18.
A method of synthesizing hitherto unknown 1-aroxysilatranes
(R=aryl) is worked out. It is based on transesterification of lower tetraalkoxysilanes with an equimolecular mixture of triethanolamine and the appropriate phenol (naphthol). Using the method, 12 compounds of the indicated type have been prepared and characterized, the yields in the main exceeding 90%.For Part VII see [1]. 相似文献
19.
The enthalpies and entropies of evaporation of Al(CH3)3–Sn(CH3)4and Ga(CH3)3–Sn(CH3)4solutions were determined. It was established that solvates are formed in these systems and that the dissociation energies of specific interactions in them change in the following order:
(10.3) >
>
>
(4.08 kJ mol–1),
(6.52) >
(5.14) >
>
(4.08 kJ mol–1). 相似文献
20.
Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C 总被引:1,自引:0,他引:1
The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO3, KBr, KI, KNO3, CaCl2, SrCl2, BaCl2, Li2SO4, K2SO4, Mn(NO3)3)] as a function of concentration at 25°C. The solubilities, mol (kg-H2O)–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg–1)
where A and B are adjustable parameters and the activity coefficient of oxygen )O2) = [O2]0/[O2]. The limiting salting coefficient, k
S = (ln / m)m=0 = A, was determined for all salts. The salting coefficients for the chlorides and sodium salts showed a near linear correlation with the crystal molar volume V
cryst = 2.52 r
3. The salting coefficients determined from the Scaled Particle Theory were in reasonable agreement with the measured values. The activity coefficients of oxygen in the solutions have been interpreted using the Pitzer equation
where
is a parameter that accounts for the interaction of O2 with cations (c) and anions (a) with molalities m
a and m
c, and
accounts for interactions for O2 with the cation and anion pair (c-a). The
and
coefficients determined for the most of the ions are in reasonable agreement with the tabulations of Clegg and Brimblecombe. The values of
for most of the ions are a linear function of the electrostriction molar volume (Velect = V0 – V
cryst). 相似文献