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951.
Conductance data for sodium nitrite, chloride, and acetate in water andN,N-dimethylformamide (DMF)-water mixtures (74.82D42.48) for the concentration range 0.001–0.04N, as well as the densities, viscosities, and dielectric constants of the solvent mixtures at 35°C, are reported. The data have been analyzed by the Fuoss (1975) equation. The existence of a maximum in the viscosity at a 13 mole ratio of DMF and water is indicated. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with increasing DMF content. The maxima in the Walden product are attributed to the dehydration of ions by the cosolvent (DMF).Part I:Indian J. Chem.
14A, 1015 (1976).Deceased. 相似文献
952.
The first thermodynamic dissociation constants of o-phthalic acid were determined at five temperatures from 278.15 to 318.15 K in 10, 14.93 and 20 wt% isopropanol-water solvent mixtures, by precise e. m. f. measurements of hydrogen-silver chlorld electrodes in cells without liquid junction. On the basis of Pitzer's theory, the method of polynomial approximation was used to determine the dissociation constants of H_2P and the results obtained were compared with traditional extrapolation according to the extended Debye-Huckel equation Results obtained from both methods agree within experimental error. The dependence of the first thermodynamic dissociation constant on temperature was given as a function of the thermodynamic temperature T by the empirical equation: pK_1=A_0+A_1/T+A_2/T. The thermodynamic quantities of dissociation in the mixed solvents have been calculated, and the results have been discussed. 相似文献
953.
Martina Dotzler Astrid Schmidt Jochen Ellermann Falk A. Knoch Matthias Moll Walter Bauer 《Polyhedron》1996,15(24):4425-4433
BiBr3 or SbI3 react at 20°C with LiN(PPh2)2 (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph2P---N=PPh2---PPh2=N---PPh2 (2). The reaction of AsI3 with 1 at room temperature formed yellow needles of the eight-membered heterocycle
(3), whereas AsI3 interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI3 and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis. 相似文献
954.
The performance of a PTV injector operated in the solvent venting mode with Tenax in the glass insert was evaluated with synthetic mixtures containing 5 to 50 ng of n-alkanes, ethyl esters, n-alcohols, and carboxylic acids. The influence of the sampled amount, the injected volume, and the nature of the solvent on accuracy and precision were studied. Coefficients of variation of relative (normalized) peak areas and absolute peak area ratios of each compound to the standard are of the order of 5 %. 相似文献
955.
956.
V. V. Lipson V. V. Borodina M. G. Shirobokova S. M. Desenko O. V. Shishkin R. I. Zubatyuk 《Chemistry of Heterocyclic Compounds》2007,43(4):490-495
Interaction of 3-amino-5-methylpyrazole, 3-amino-5-methylthio-, and 3,5-diamino-1,2,4-triazole with Meldrum’s acid, acetone,
ethyl methyl ketone, and cyclohexanone leads to alkyl-substituted pyrazolo[3,4-b]pyridin-6-ones and 1,2,4-triazolo[1,5-a]pyrimidin-7-ones
respectively. The structure of 5,5-dimethyl-2-methylthio-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidin-7-one was demonstrated
by an X-ray structural investigation.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 595–601, April, 2007. 相似文献
957.
Junyong Wu Jingchang Zhang Zhaoxu Wang Weiliang Cao 《International journal of quantum chemistry》2007,107(9):1897-1906
By counterpoise‐corrected optimization method, the interactions of BrCl with the first‐row hydrides (HF, H2O, NH3) have been investigated at the MP2/6–311++G(3d,3p) level. To understand that the X? Br‐type (X = F, O, N) structure is more stable than the corresponding hydrogen‐bonded structure in these complexes, the electronic properties were also investigated. Symmetry‐adapted perturbation theory (SAPT) analysis has been carried out to understand the nature of the weak hydrogen bond and X? Br‐type interactions. On the other hand, for the weak hydrogen‐bonded complexes and the X? Br‐type complexes charges transfer is well correlated with the total induction energies. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
958.
Multiple zigzag chains of length n and width m constitute an important class of regular graphene flakes of rectangular shape. The physical and chemical properties of these basic pericondensed benzenoids can be related to their various topological invariants, conveniently encoded as the coefficients of a combinatorial polynomial, usually referred to as the ZZ polynomial of multiple zigzag chains . The current study reports a novel method for determination of these ZZ polynomials based on a hypothesized extension to John–Sachs theorem, used previously to enumerate Kekulé structures of various benzenoid hydrocarbons. We show that the ZZ polynomial of the multiple zigzag chain can be conveniently expressed as a determinant of a Toeplitz (or almost Toeplitz) matrix of size consisting of simple hypergeometric polynomials. The presented analysis can be extended to generalized multiple zigzag chains , i.e., derivatives of with a single attached polyacene chain of length k. All presented formulas are accompanied by formal proofs. The developed theoretical machinery is applied for predicting aromaticity distribution patterns in large and infinite multiple zigzag chains and for computing the distribution of spin densities in biradical states of finite multiple zigzag chains . 相似文献
959.
The considered mathematical model of the decomposition of valerate presents three unknown kinetic parameters, two unknown
stoichiometric coefficients, and three unknown initial concentrations for biomass. Applying a structural identifiability study,
we concluded that it is necessary to perform simultaneous batch experiments with differenitial conditions for estimating these
parameters. Four simultaneous batch experiments were conducted at 55°C, characterized by four different initial acetate concentrations.
Product inhibition of valerate degradation by acetate was considered. Practical identification was done optimizing the sum
of the multiple determination coefficients for all measured state viariables and for all experiments simultaneously. The estimated
values of kinetic parameters and stoichiometric coefficients were characterized by the parameter correlation matrix, the confidence
interval, and the student's t-test at 9% significance level with positive results except for the saturation constant, for which more eperiments for improving
its identifiability should be conducted. In this article, we discussekinetic parameter estimation methods. 相似文献
960.
(Z)-γ-Cyano-β-perfluoroalkyl-β,γ-unsaturated esters have been synthesized by the reaction of perfluoroacylated phosphonates with organozinc reagent in 50-71% (three steps) yields. 相似文献