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71.
The synthesis of CF(3)OC(O)OOC(O)F is accomplished by the photolysis of a mixture of (CF(3)CO)(2)O, FC(O)C(O)F, CO, and O(2) at -15 degrees C using a low-pressure mercury lamp. The new peroxide is obtained in pure form in low yield after repeated trap-to-trap condensation and is characterized by NMR, IR, Raman, and UV spectroscopy. Geometrical parameters were studied by ab initio methods [B3LYP/6-311+G(d)]. At room temperature, CF(3)OC(O)OOC(O)F is stable for many days in the liquid or gaseous state. The melting point is -87 degrees C, and the boiling point is extrapolated to 45 degrees C from the vapor pressure curve log p = 8.384 - 1715/T (p/mbar, T/K). A possible mechanism for the formation of CF(3)OC(O)OOC(O)F is discussed, and its properties are compared with those of related compounds. 相似文献
72.
The trioxide, CF(3)OC(O)OOOC(O)OCF(3), reacts with NO(2) at 0 degrees C to yield the new peroxynitrate, CF(3)OC(O)OONO(2), which is stable for hours at room temperature. It is spectroscopically characterized and some thermal properties are reported. From the vapor pressure, ln(p/p(0)) = 14.06 - 4565/T, of the liquid above the melting point of -89 degrees C, the extrapolated boiling point is 52 degrees C. CF(3)OC(O)OONO(2) dissociates at higher temperatures and low pressures into the radicals CF(3)OC(O)OO and NO(2) as demonstrated by matrix isolation experiments. The matrix-isolated peroxy radicals consist in a rotameric mixture of trans,trans,trans-CF(3)OC(O)OO and trans,trans,cis-CF(3)OC(O)OO, where trans and cis denote dihedral angles of ca. 180 degrees and 0 degree, respectively, around beta F-C-O-C, beta C-O-C-O, and beta O-C-O-O, with an equilibrium composition dependent on the thermolysis temperature. The radical trans,trans,cis-CF(3)OC(O)OO is found to be ca. 3 kJ mol(-1) higher in enthalpy than trans,trans,trans-CF(3)OC(O)OO. DFT calculations are performed to support the vibrational assignments and to provide structural information about CF(3)OC(O)OONO(2). 相似文献
73.
I. L. Davies M. W. Raynor D. J. Urwin K. D. Bartle M. Tolay E. Ekinci H. E. Schwartz 《Journal of separation science》1988,11(11):792-799
This work describes the analysis of a pyrolysis product of a lignite sample obtained from the Turkish Goynuk reserve. The aliphatic, aromatic and polar compounds present in the tar are separated and identified by various chromatographic techniques: Capillary gas chromatography/mass spectrometry (GC/MS), on-line high performance microbore liquid chromatography/capillary gas chromatography (LC/GC) and capillary supercritical fluid chromatography (SFC). The suitability of each technique for this particular application is discussed, and semi-quantitative results are presented for the major components detected. 相似文献
74.
A. Gustavo González M. Ángeles Herrador Agustín G. Asuero 《Accreditation and quality assurance》2005,10(7):386-391
The uncertainty evaluation of mass measurements when using “in-house” calibrated analytical balances is revisited according
to the Guide to the expression of Uncertainty Measurement (GUM). The calibration of analytical balances is discussed according
to the guidelines of several bodies such as ASTM, UKAS and DKD/PTB. The remainder components of uncertainty can be estimated
from the balance data sheet specifications. 相似文献
75.
We employ the Laplace-transformed second-order Moller-Plesset perturbation theory for periodic systems in its atomic orbital basis formulation to determine the geometric structure and band gap of interacting polyacetylene chains. We have studied single, double, and triple chains, and also two-dimensional crystals. We estimate from first principles the equilibrium interchain distance and setting angle, along with binding energy between trans-polyacetylene chains due to dispersion interactions. The dependence of the correlation corrected quasiparticle band gap on the intrachain and interchain geometric parameters is studied, obtaining that the gap of the compound structures is substantially reduced with respect to the single chain polymer. 相似文献
76.
Patrick Gredin Ariel De Kozak Michel Quarton Jean Renaudin Grard Ferey 《无机化学与普通化学杂志》1993,619(6):1088-1094
The liquid-solid phase diagram of the binary system BaF2? ScF3 is established by D.T.A. and radiocrystallography. Three fluorides are disclosed: Ba3Sc2F12, Ba5Sc3F19 and a cubic high temperature phase Ba1?xScxF2+x (x = 0.17), the structure of which derives from that of BaF2. A solid solution between BaF2 and ScF3 is also evidenced at high temperature. The ternary system BaF2? CuF2? ScF3 is investigated by radiocrystallography and an isothermal section at 670°C is given. It shows the existence of four phases: a complex quaternary fluoride Ba10Cu12ScF47, two “polytypic” phases the structure of which derives from that of BaCuF4 and a tetragonal solid solution Ba5Sc3?xCuxF19?x with 0 ≤ x ≤ 1. 相似文献
77.
Marco Biddau Marcella Massacesi Rosalba Pinna Gustavo Ponticelli 《Transition Metal Chemistry》1977,2(1):5-9
Summary Complexes of cobalt(II) and copper(II) with 5-amino-3,4-dimethylisoxazole (5-ADI) have been prepared and studied by means of magnetic susceptibility measurements, near and far i.r. spectra, electronic spectroscopy and, when possible, conductivity measurements. The 5-ADI generally behaves as bridging (Nring-, O- or Nring-, -NH2) ligand. All the complexes have an octahedral sterochemistry, except Co(5-ADI)2X2 (X = Cl, Br), Co2(5-ADI)7I4 which are tetrahedral and Cu(5-ADI)2 (ClO4)2 · 4 H2O which is square planar. 相似文献
78.
Mariana Ramos-Estrada Gustavo A. Iglesias-Silva Kenneth R. Hall F. Kohler 《Fluid Phase Equilibria》2006,240(2):179-185
We use the Clausius–Clapeyron equation to calculate third virial coefficients at low reduced temperatures. This procedure gives an alternative to predict third virial coefficients in a region where the third virial coefficient is difficult to measure. We compare the results of this method with published third virial coefficient data. Calculated third virial coefficients have average percentage deviations within 5% of the experimental values at reduced temperatures between 0.8 and 1.0. 相似文献
79.
Molecular dynamics simulations are used to calculate the melting point and some aspects of high-temperature solid-state phase transitions of ammonium nitrate (AN). The force field used in the simulations is that developed by Sorescu and Thompson [J. Phys. Chem. A 105, 720 (2001)] to describe the solid-state properties of the low-temperature phase-V AN. Simulations at various temperatures were performed with this force field for a 4 x 4 x 5 supercell of phase-II AN. The melting point of AN was determined from calculations on this supercell with voids introduced in the solid structure to eliminate superheating effects. The melting temperature was determined by calculating the density and the nitrogen-nitrogen radial distribution functions as functions of temperature. The melting point was predicted to be in the range 445 +/- 10 K, in excellent agreement with the experimental value of 442 K. The computed temperature dependences of the density, diffusion, and viscosity coefficient for the liquid are in good agreement with experiment. Structural changes in the perfect crystal at various temperatures were also investigated. The ammonium ions in the phase-II structure are rotationally disordered at 400 K. At higher temperatures, beginning at 530 K, the nitrate ions are essentially rotationally unhindered. The density and radial distribution functions in this temperature range show that the AN solid is superheated. The rotational disorder is qualitatively similar to that observed in the experimental phase-II to phase-I solid-state transition. 相似文献
80.
Patrick Gredin Gwenaël Corbel Jonathan P. Wright Nathalie Dupont Ariel de Kozak 《无机化学与普通化学杂志》2003,629(11):1960-1964
Ba3Cu2Al2F16 is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P21 (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with Fo/σ(Fo) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated [(AlF5)2]∞4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra [AlF6], linked by two vertices and distanced by a. The second one, formulated [Cu2AlF11]∞4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra [CuF6], linked by edges, which form infinite chains interconnected by three vertices of isolated [AlF6] octahedra. The stacking sequence of the sheets is (A, B, B)∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba3Cu2Al2F16 is closely related to that of Ba4Cu2Al3F21. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries. 相似文献