ICP-AES法测定石灰石、白云石中的Al_2O_3,CaO,TFe_2O_3,MgO,MnO,SiO_2,TiO_2

采用无水碳酸钾＋硼酸处理样品,电感耦合等离子体发射光谱法同时测定石灰石及白云石中7种组分,筛选了不同仪器参数条件,对各组分分别选用2条相对谱线强度适中的谱线进行分析,并以元素平均值的模式输出数据结果,测定的相对标准偏差小于0.60%.经对国家一级石灰石及白云石标准物质分析验证,结果与标准值吻合.     

连续二氧化碳激光敏化氧化CF2HCL,CF2=CF2,CF2=CFCl,CHCl3,CHCl=CCl2和CH2=CH2

本文报道了连续二氧化碳激光敏化氧化CF_2HCl,CF_2==CF_2,CF_2==CFCL,CHCl_3,CHCl==CCl_2和CH_2==CH_2的反应,讨论了某些反应的机制。结果表明,激光敏化方法可以使不能直接吸收激光的反应物分子在气相中发生反应,并有可能产生卡宾。     

穴醚[2, 2, 2]和穴醚[2, 2]对镉离子萃取行为的研究

本文研究了穴醚[2,2,2]和穴醚[2,2]在硝基甲烷中对镉的萃取行为。探讨了溶剂、穴醚浓度,碱浓度,无机酸浓度,盐效应及共存离子对镉萃取的影响。实验结果表明,硝基甲烷ε=35.6,μ=3.4德拜宜作为穴醚的溶剂。当穴醚[2,2,2]——硝基甲烷的浓度为2×10~(-3)M,Me_4NOH浓度为4×10~(-2)M时对镉的萃取最为有利。无机酸的引入使穴醚质子化程度加大,盐效应对镉的萃取无明显影响。十八种共存离子对镉萃取无干扰,因而选择性高。实验结果为用穴醚[2,2,2]萃取镉提供了依据。     

CRYSTAL STRUCTURE OF 2, 4-DITHIONE-3-AMINO-1, 3, 2-OX-AZAPHOSPHORINEBENZO-2-THIONO PYRIDINIUM

<正> The structure of title compound [C7H6N2OPS3]-·[HNC5H5]+ was determined by x-ray diffraction. It belongs to monoclinic system with space group P21/a, a = 16.745(2), b= 8.563(2), c=21. 050(5)(?), β=93.32(1)°, V= 3013. 6(?)3, Z = 8, Mr = 341. 4, F (000) = 1536, Dc=1. 504 g. cm-3,μ= 53. 0 cm-1. The crystal is composed of discrete cations C5H5NH+ and anions CrH6N2OPS3-. There are two pairs of the cations and the anions in each asymmetric unit. The stability of the anion is increased by the formation of (d-p)π bonding involving the 3d orbital of the P atom and the lone electron pairs of the S atoms.     

SiO2,Al2O3上涂载TiO2,ZrO2,La2O3制备Pd催化剂的研究

采用浸渍法制备了Ｌａ２Ｏ３，ＴｉＯ２，ＺｒＯ２以单层状态分散在ＳｉＯ２，Ａｌ２Ｏ３上的改性载体。用ＸＰＳ求得它们的最大单层分散阈值为：０．２２ｇＬａ２Ｏ３／１００ｍ＾２ＳｉＯ２，０．２７ｇＬａ２Ｏ３／１００ｍ＾２Ａｌ２Ｏ３，０．０４ｇＴｉＯ２／１００ｍ＾２ＳｉＯ２，０．０３６ｇ ＴｉＯ２／１００ｍ＾２Ａｌ２Ｏ３，０．０７ｇＺｒＯ２／１００ｍ＾２ＳｉＯ２，０．０８ｇＺｒＯ２／１００ｍ＾２Ａｌ２Ｏ３．     

Aggregation Stability of SiO2, FeOOH, ZrO2, CeO2, and Natural Diamond Sols and Their Binary Mixtures: 2. The Photometric Study of Heterocoagulation of SiO2–FeOOH, SiO2–ZrO2, SiO2–CeO2, and CeO2–Natural Diamond Binary Systems in KCl Solutions

The aggregation stability of 1 : 1 and 3 : 1 (by volume) binary mixtures of two hydrophobic (SiO₂–FeOOH), one hydrophobic and one hydrophilic (SiO₂–ZrO₂, SiO₂–CeO₂), and two hydrophilic (CeO₂–natural diamond) sols was studied by photometry over a wide range of KCl concentrations at pH 6 and 3. The stability of the mixed binary sols was determined by the stability of the sol with a predominant particle number concentration. In the SiO₂–FeOOH system, the phenomenon of heteroadagulation stabilization was caused by the electrostatic factor of the stability of adsorbed SiO₂ particles and, in the SiO₂–ZrO₂ system, by the structural factor of the stability of adsorbed hydrophilic ZrO₂ particles. The stability of binary mixtures containing one or two hydrophobic components is qualitatively explained in terms of the Derjaguin theory of heterocoagulation of hydrophobic colloids. The stability of the binary system of two hydrophilic components (CeO₂–natural diamond) is determined by the structural component of the interaction energy of particles.     

Geometric shielding corrections for calculation of electron scattering by CO2, C2H2, CHCl3, CH2Cl2, CH3Cl,CHF3, CH2F2 and CH3F at 30–5000 eV

Taking into account the changes of the geometric shielding effect in a molecule as the incident electron energy varies, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using the new additivity rule, the total cross sections of electron scattering by CO₂, C₂H₂, CHCl₃, CH₂Cl₂, CH₃Cl, CHF₃, CH₂F₂ and CH₃F are calculated at the Hartree–Fork level at 30–5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, especially above 100 eV.     

双核钯配合物Pd2L2和Pd2L2X2(L=Me2PCH2PMe2;X=F,Cl,Br,I,H)的量子化学理论研究

采用 ab initio HF,MP2方法和密度泛函理论方法,对Pd(0),Pd(Ⅰ)双核配合物Pd2L2和Pd2L2X2(L=Me2PCH2PMe2;X=F,Cl,Br,I,H)的儿何结构和电子结构进行了研究.研究表明Pd2L2中Pd原子间的相互作用丰要来自电子相关效应,Pd2L2X2中Pd原子问的相互作用则主要来自d轨道的成键作用.MP2方法和局域泛函Xa方法能对两类配合物的几何结构给予准确的描述.在Pd2L2中,Pd原子的4d电了组成一一对应的成键、反键轨道,轨道作用相互抵消使Pd原子间仅存在微弱的相互作用.x原子与Pd2L2的作用使Pd-Pd反键轨道电子占据数减少,成键作用加强.两类配合物的Pd-Pd键长与NAO键级之间存在很好的线性关系.还对Pd2L2和Pd2L2X2的低占据电子激发态进行了含时密度泛函理论计算,分析不同配合物的电子跃迁特征,并就卤素配体对Pd2L2X2光谱性质的影响进行了讨论.     

Rhodium-Catalyzed Chemo-, Regio-, Diastereo-, and Enantioselective Intermolecular [2+2+2] Cycloaddition of Three Unsymmetric 2π Components

We have developed the Rh⁺/H₈-binap-catalyzed chemo-, regio-, diastereo-, and enantioselective intermolecular [2+2+2] cycloaddition of three unsymmetric 2π components. Thus, two arylacetylenes react with a cis-enamide to yield a protected chiral cyclohexadienylamine. Moreover, replacing one arylacetylene with a silylacetylene enables the [2+2+2] cycloaddition of three distinct unsymmetric 2π components. These transformations proceed with excellent selectivity (complete regio- and diastereoselectivity and up to >99 % yield and >99 % ee). Mechanistic studies suggest the chemo- and regioselective formation of a rhodacyclopentadiene intermediate from the two terminal alkynes.     

Infrared spectra of Rh atom reaction products with C2H2: the HRhCCH, RhCCH, RhCCH2, and Rh-η2-C2H2 molecules

Laser-ablated Rh atoms react with C(2)H(2) upon co-condensation in excess argon and neon to form the insertion product HRhCCH, the alkyne RhCCH, the vinylidene RhCCH(2), and the metallacycle complex Rh-η(2)-(C(2)H(2)). These species are identified through (13)C(2)H(2), C(2)D(2), and mixed C(2)HD isotopic substitutions and density functional theory isotopic frequency calculations. The HRhCCH molecule is characterized by the CH stretching mode at 3306.2 cm(-1) (Ar) and 3310.9 cm(-1) (Ne), the Rh-H stretching mode at 2090.8 cm(-1) (Ar) and 2111.0 cm(-1) (Ne), and two CCH deformation modes at 584.3 and 573.3 cm(-1) (Ar) and 587.1 and 580.3 cm(-1) (Ne). The absorptions for the vinylidene RhCCH(2) complex are observed at 3150.9 (Ar), 3147.2 (Ne) (CH stretching), 1690.1 (Ar), 1694.3 (Ne) (CC stretching), and 804.9 (Ar), 810.5 cm(-1) (Ne) (CCH deformation). The metallacycle Rh-η(2)-(C(2)H(2)) complex is also identified through CC stretching and CCH deformation modes. The insertion reaction of ground Rh atom to the C-H bond is spontaneous on the basis of the growth of HRhCCH absorptions upon annealing in both solid neon and argon. Here, we show that atomic Rh can convert acetylene to the simple Rh vinylidene complex, analogous to that found for ligand-supported Rh complexes.     

Structures, energies, bonding, and NMR properties of pnicogen complexes H2XP:NXH2 (X ═ H, CH3, NH2, OH, F, Cl)

Ab initio calculations have been carried out in a systematic investigation of P···N pnicogen complexes H(2)XP:NXH(2) for X ═ H, CH(3), NH(2), OH, F, and Cl, as well as selected complexes with different substituents X bonded to P and N. Binding energies for complexes H(2)XP:NXH(2) range from 8 to 27 kJ mol(-1) and increase to 39 kJ mol(-1) for H(2)FP:N(CH(3))H(2). Equilibrium structures have a nearly linear A-P-N arrangement, with A being the atom directly bonded to P. Binding energies correlate with intermolecular N-P distances as well as with bonding parameters obtained from AIM and SAPT analyses. Complexation increases (31)P chemical shieldings in complexes with binding energies greater than 19 kJ mol(-1). One-bond spin-spin coupling constants (1p)J(N-P) across the pnicogen interaction exhibit a quadratic dependence on the N-P distance for complexes H(2)XP:NXH(2), similar to the dependence of (2h)J(X-Y) on the X-Y distance for complexes with X-H···Y hydrogen bonds. However, when the mixed complexes H(2)XP:NX'H(2) are included, the curvature of the trendline changes and the good correlation between (1p)J(N-P) and the N-P distance is lost.     

XPS primary excitation spectra of Zn 2p,Fe 2p,and Ce 3d from ZnO, α-Fe2O3, and CeO2

Metal oxides are important for current development in nanotechnology. X-ray photoelectron spectroscopy(XPS) is a widely used technique to study the oxidation states of metals, and a basic understanding of the photoexcitation process is important to obtain the full information from XPS. We have studied core level excitations of Zn 2p, Fe 2p, and Ce 3d photoelectron emissions from ZnO, α-Fe₂O₃, and CeO₂. Using an effective energy-differential XPS inelastic-scattering cross section evaluated within the semiclassical dielectric response model for XPS, we analysed the experimental spectra to determine the corresponding primary excitation spectra, ie, the initial excitation processes. We find that simple emission (Zn 2p) as well as complex multiplet photoemission spectra (Fe 2p and Ce 3d) can be quantitatively analysed with our procedure. Moreover, for α-Fe₂O₃, it is possible to use the software package CTM4XAS (Charge Transfer Multiplet program for X-ray Absorption Spectroscopy) to calculate its primary excitation spectrum within a quantum mechanical model, and it was found to be in good agreement with the spectrum determined by analysis of the experiment.     

Heat capacities of 15Na2O·10(MgO,CaO, TiO2, ZrO2)·75SiO2 glasses

Heat capacitiesC _p of title glasses were measured for temperature ranging from 50 to 550°C. True linear temperature dependences were observed for all studied glasses at temperatures sufficiently lower than the glass transition temperature. The temperature-compositionalC _p dependence was described by the linear model with only statistically significant coefficients retained. The parameters were estimated using the standard least squares procedure. The results obtained may be used for evaluation of viscosity values according to Adam and Gibbs theory.This work was supported by the Slovak Grant Agency for Science under the grant No. 1171/95.     

Complexes H2CO:PXH2 and HCO2H : PXH2 for X=NC,F, Cl,CN, OH,CCH, CH3, and H: Pnicogen Bonds and Hydrogen Bonds

Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to investigate H₂CO : PXH₂ pnicogen-bonded complexes and HCO₂H : PXH₂ complexes that are stabilized by pnicogen bonds and hydrogen bonds, with X=NC, F, Cl, CN, OH, CCH, CH₃, and H. The binding energies of these complexes exhibit a second-order dependence on the O−P distance. DFT-SAPT binding energies correlate linearly with MP2 binding energies. The HCO₂H : PXH₂ complexes are stabilized by both a pnicogen bond and a hydrogen bond, resulting in greater binding energies for the HCO₂H : PXH₂ complexes compared to H₂CO : PXH₂. Neither the O−P distance across the pnicogen bond nor the O−P distance across the hydrogen bond correlates with the binding energies of these complexes. The nonlinearity of the hydrogen bonds suggests that they are relatively weak bonds, except for complexes in which the substituent X is either CH₃ or H. The pnicogen bond is the more important stabilizing interaction in the HCO₂H : PXH₂ complexes except when the substituent X is a more electropositive group. EOM-CCSD spin-spin coupling constants ^1pJ(O−P) across pnicogen bonds in H₂CO:PXH₂ and HCO₂H : PXH₂ complexes increase as the O−P distance decreases, and exhibit a second order dependence on that distance. There is no correlation between ^2hJ(O−P) and the O−P distance across the hydrogen bond in the HCO₂H : PXH₂ complexes. ^2hJ(O−P) coupling constants for complexes with X=CH₃ and H have much greater absolute values than anticipated from their O−P distances.