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1.
2.
High-resolution infrared studies of isotopic ethylenes below 2000 cm?1 have been commenced with a Nicolet FTIR spectrometer. Accurate vibration and rotation parameters for the v12 fundamentals of C2H4 and C2D4 are determined from spectra recorded with 0.05 cm?1 resolution. Excellent band contour simulations confirm that these bands are unperturbed throughout their range.  相似文献   

3.
Experimental differential cross sections for 40 keV electrons scattered by C2H2, C2H4 and C2H6 molecules were measured using the gas electron diffraction method in the range of the scattering variable s from s = 1 A?1 to s = 30 A?1. The differential cross sections for neon were also measured and compared with calculated differential cross sections to calibrate the diffractograph. Experimental differential cross sections show significant deviations with respect to theoretical differential cross sections calculated from the Debye-Ehrenfest model, mainly in the range of small scattering angles. The observed differences are connected to chemical binding effects. From the experimental data, an estimation of the binding energy was carried out. The deduced values: ?0.58 ± 0.20 au for C2H2, ?0.94 ± 0.30 au for C2H4 and ?1.23 ± 0.40 au for C2H6 are in agreement with those obtained by thermochemical methods.  相似文献   

4.
C2(a 3πu) disappearance rate constants of 1.44, 0.96, 0.0296, 0.0130 and < 10?6(x10?10cm3s?1) are reported for reactions with C2H4, C2H2, O2, C2H6, and CH4, respectively at 298 K. C2(a 3πu) fragments are generated by multiphoton ArF excimer laser photodissociation at C2H2, and monitored by dye laser induced fluorescence. Arguments are presented which favor chemical reactions over the C2(a 3πu) → (X 1σ+g) quenching channel. C2 + C2H2 represents the one possible exception to the reactive channel.  相似文献   

5.
A simple one-step preparation of the sulfones of Leukotriene C4, D4 and E4 has been developed by the direct oxidation of the parent compounds. An alternative synthesis of these sulfones has also been carried out by reduction of an acetylenic precursor.  相似文献   

6.
The adsorption of C2H4 on W(100) has been studied by ultraviolet photoelectron spectroscopy with hν = 21.22 eV. The spectrum measured after in initial saturation exposure at 80 K exhibits structure which correlates well with energy levels recently calculated by Demuth and Eastman (DE) for sp3 rehybridized C2H4. Dehydrogenation of the adsorbate, either by subsequent heating to 295 K or direct adsorption at 295 K, yields a spectrum which correlates with DE's calculation for sp2 rehybridized C2H2. These results suggest that C2H4 and C2H2 may be distorted from their planar and linear structures respectively and that the CC bonds on these molecules are stretched by adsorption on W(100). Qualitative arguments suggest that the bonding site for both melecules is directly over a W atom and that the Dewar—Chatt model for πd bonding in organometallic compounds is applicable.  相似文献   

7.
The results of several MC SCF calculations on CH4, C2H4 and C2H6 with minimun bases of Slater type AO's are reported. The computing method is a quadratically convergent process. Better final energies are obtained if localized MO's are used.  相似文献   

8.
High pressure vapour-liquid equilibrium data for the C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2 systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.  相似文献   

9.
Au/H 相似性的研究是现代化学中的一个热门话题. 我们从理论上报道Au/H 相似的新成员: 共价化合物B2Au4, 离子化合物Al2Au4和BAlAu4. 采用密度泛函和波函数理论方法对比研究了缺电子体系B2Au4、Al2Au4和BAlAu4的几何和电子结构. 详细讨论了它们基态结构的轨道、适应性自然密度划分(AdNDP)和电子局域函数(ELF)分析. 计算结果表明稍微扭曲变形的C2B2Au4是基态结构, 在这个共价化合物中含有两个B―Au―B三中心二电子(3c-2e)键. 然而C3v Al+(AlAu4)-和C3v Al+(BAu4)-被研究证明是含有三个X―Au―Al 三中心二电子键的类盐化合物(在Al2Au4中X=Al, BAlAu4中X=B). Al2Au4和BAlAu4是至今为止首例报道的在离子缺电子体系中含有金桥键的化合物. 同时计算了B2Au4-、Al2Au4- 和BAlAu4- 阴离子基态结构的绝热剥离能和垂直剥离能, 为实验表征提供依据. 文中报道的金桥键为共价键和离子键相结合的缺电子体系提供了一个有趣的键合模式, 有助于设计含有高度分散金原子的新材料和催化剂.  相似文献   

10.
A gas phase electron diffraction study of the cage hydrocarbon, basketene, is reported. A least squares treatment of molecular intensities has been carried out in terms of a geometrically consistent rα structure. The mean amplitude values and shrinkage corrections have been calculated using the force field parameters estimated from the data on simpler molecules.Structure refinement of the C2v molecular model yields the following parameter values (bond lengths, ra, in nm; angles, rα in degrees): <C2—C3, C4—C5?av 0.1609(14); C3—C4 0.1563(6); C9C10 0.1360(9); C1—C10 0.1511(13); C1—C2 0.1517(9); <C-H>av. 0.1092(8); <C3C4C7 88.5(1.0); dihedral angle C3C4C7/C3C5C7 153.8(1.0). Parenthesized are three times the standard deviation values, 3σ.In addition to the geometric parameters listed, the mean amplitudes for all bonded and C· C nonbonded distances have been determined by the least squares method. All the other amplitudes (C· H and H· H) have been fixed at the values estimated from the spectral data.Comparison of the results obtained with the literature data on similar polycyclic molecules points to the stronger internal strain in the basketene molecule.  相似文献   

11.
We present a new experimental determination of the Compton profiles of CH4 and C2H4 molecules using high energy electron impact. The observable q range has been extended up to 10 au (6 au for C2H4). Good agreement is found with an earlier X-ray scattering experiment and with new theoretical calculations.  相似文献   

12.
13.
Enthalpies of formation of ground states of the gaseous particles CF, CF2, C2F5, CF4, CF3I, C2F4, and C2F6 were calculated by ab initio method in the CCSD(T) approximation with extrapolation to the full basis and regard to the correlation energy. Their equilibrium geometrics, frequencies of normal vibrations, and other values were found by the B3LYP/aug-cc-pvdz method, from which thermodynamic functions within the range of 0–6000 K were calculated. Equilibrium constants were calculated from these functions, and then the information on the rate constants in the limit of high pressures was obtained.  相似文献   

14.
The IR and Raman spectra of solid and dissolved S4N4, S4N4H4, S4N4D4 and S3N3Cl3 have been recorded and are assigned according to D2d, C4v and C3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.  相似文献   

15.
The low-lying isomers of Al2H4 and their anions are investigated with the hybrid density functional B3LYP, the coupled-cluster CCSD and CCSD(T) methods, and the electron propagator theory. The positive adiabatic electron affinities 5,798 and 10,112 cm−1 are predicted for the neutral C2v and D2d symmetric isomers, respectively. The D2h symmetric anion is more stable by 852 cm−1 than the C2v symmetric anion. The photodetachment spectra for Al2H4 anions at the C2v and D2h symmetries are simulated on the basis of the Franck–Condon factor calculations, indicating a reasonable way to study the transition state of the intramolecular torsion process  相似文献   

16.
Results of valence electron SCF-MO calculations in the INDO approximation predict a value of 102° for the apex angle of C2v-‘V’ structure of B2O3, assuming bond lengths obtained from electron diffraction work. Calculated results for the dipole moment are reported and electron population analysis is used to discuss bonding.  相似文献   

17.
The vibrational spectra of nickel and magnesium α-pyrophosphates and of potassium and sodium α-pyroarsenates were found. A normal coordinate analysis was carried out for both P2O7 and As2O7 molecular systems using the force field of the Urey-Bradley-Shimanouchi type and the C2v symmetry model. On the basis of the results obtained the significant differences between the temperatures of the α/β phase transitions observed for Mg (68 °C) and Ni (565 °C) pyrophosphates have been explained.  相似文献   

18.
An experimental study on the conversion of NO in the NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N2 system, NO decomposition to N2 and O2 is the dominating reaction; NO conversion to NO2 is less significant. O2 produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O2 produced decreases at 298 K, but slightly increases at 523 K. In the NO/O2/N2 system, NO is mainly oxidized to NO2, but NO conversion becomes very low at 523 K and over 1.6% of O2. In the NO/C2H4/N2 system, NO is reduced to N2 with about the same NO conversion as that in the NO/N2 system but without NO2 formation. In the NO/C2H4/O2/N2 system, the oxidation of NO to NO2 is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO2 selectivity in the energy density range of 317–550 J L−1. It finally decreases gradually at high energy density. A negligible amount of N2O is formed in the above four systems. Of the four systems studied, NO conversion and NO2 selectivity of the NO/C2H4/O2/N2 system are the highest, and NO/O2/C2H4/N2 system has the lowest electrical energy consumption per NO molecule converted.  相似文献   

19.
The molecular structure of tungsten oxytetrafluoride has been studied in the gas phase by electron diffraction. A square pyramidal model with molecular symmetryC4v, as indicated by vibrational spectroscopy, gives a good fit to the experimental data. Least squares refinement on the molecular intensity curves gives the following results for the principal geometrical parameters (uncertainties in parentheses are 2σ):ra(W=O) = 1.666 (0.007)Å,ra(W-F)= 1.847 (0.002)Å, ∠OWF = 104.8 (0.6)°, ∠FWF = 86.2(0.3)°.  相似文献   

20.
Differences between SiH+5 and CH+5 are more significant than the similarities. The proton affinity of SiH4 exceeds than of CH4 by ≈25 kcal/mol. but the heat of hydrogenation of SiH+3 is smaller than that of CH+3 by nearly the same amount. Like CH+5 the C5 structures of SiH+5 are preferred, but SiH+5 is best regarded as a weaker SiH+3—H2 complex. D3h, C2v, and C4v forms are much higher in energy and SiH+5 should not undergo hydrogen scrambling (pseudorotation) readily, as does CH+5 The neutral BH5 is only weakly bound toward loss H2, and the D3h. C2v, and C4v forms are also high in energy. The contral-atom electronegativities, C+ > B > Si+, control this behavior. The electronegativities also determine the ability to bear positive charges. Thermodynamically. SiH+5 and SiH+3 are more stable than CH+5 and CH+3, respectively; hydride transfer occurs from SiH4 to CH+3 and proton transfer from CH+5 to SiH4.  相似文献   

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