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1.
Effect of SiCl 4-modified silica/MAO-supported Et[Ind] 2ZrCl 2 metallocene catalyst on copolymerization of ethylene with -olefins was investigated. Effect of SiCl 4 on activities was diminished with higher -olefins. Molecular weights of copolymers decreased with SiCl 4 modification. SiCl 4 modification also resulted in a lower molecular weight distribution. 13C NMR showed that ethylene incorporation in all systems gave copolymers with similar triad distribution. In addition, a narrow branching distribution can be achieved with SiCl 4 modification. 相似文献
2.
The reaction between SiCl 4 and O 2 at 1 atm between 25 and 1200°C has been followed by mass spectrometry. Below 600°C no reaction with O 2 is noted. Above 600°C the reaction proceeds in two steps. Between 800 and 1000°C the 28Si/ 32O 2 peak height ratio is constant with no evolution of Cl 2. It is suggested that silicon oxychlorides are being formed in this temperature regime. Above 1000°C the reaction between SiCl 4 and O 2 intensifies with concomitant production of Cl 2. It is suggested that above 1000°C the reaction SiCl 4 + O 2 → SiO 2 + Cl 2 becomes important. At low temperatures (<800°C) adsorbed H2O and OH groups from the surface of the fused silica tube react with SiCl4 to form HCl. The importance of this reaction decreases with increasing temperature. The increased production of HCl above 1000°C is ascribed to H2O and H2 diffusing from the tube. 相似文献
3.
Absolute differential photoabsorption oscillator strengths (cross sections) for the F 1s, C 1s, and Cl 2p, 2s inner shells of the freon molecules CF 3Cl, CF 2Cl 2 and CFCl 3 have been derived from high resolution electron energy loss spectra obtained under dipole dominated conditions of high impact energy (3 keV) and zero degree mean scattering angle. Differential oscillator strengths have also been obtained from earlier reported electron energy loss spectra for CF 4 and CCl 4. The spectra are analyzed using the MO picture and the potential barrier model. 相似文献
4.
Chiral δ-hydroxy-β-ketoesters are easily available through the enantioselective vinylogous aldol reaction of Chan’s diene promoted by a SiCl 4/chiral phosphoramide catalytic system. The procedure is conveniently exploited for a very rapid approach to (+)-kavain, a natural bio-active -pyrone compound. 相似文献
5.
The preparation of a series of immobilized transition-metal catalysts are reported. The catalysts were obtained by chemisorption of either rhodium(I) or iridium(I) complexes [MX(C 2H 4) 2] n (M = Rh, Ir; X = Cl, OAc, acac, f 3-acac, f 6-acac) on SiO 2 or MgO supports. The oxides were also activated by SiCl 4 or TiCl 4 to give support materials in which the acidic nature of the surface is substantially increased. The activity of the immobilized catalysts was tested, particularly in the reaction of ethene with diphenyldiazomethane which yields a mixture of 1.1-diphenylpropene (8) and 1.1-diphenylcyclopropane (9). It was found that the most active and most selective (highest ratio 8:9) catalyst B1 was formed support material B (SiO 2 activated by SiCl 4) and [RhCl(C 2H 4) 2] 2 (1) and that both the activity and selectivity of B1 was comparable with that of complex 1 in solution. In contrast, the supported catalysts A2, D2 and A3, D3 obtained from [Rh(OAc)(C 2H 4) 2] 2 (2) and [Rh(acac)(C 2H 4) 2] (3) were less active than compounds 2 and 3 in solution. The immobilized catalysts A6, A7, D7 and E7, which were generated from the chloro- and acetatoiridium(I) complexes [IrCl(C 2H 4) 2] 2 (6) and [Ir(OAc)(C 2H 4) 2] 2 (7), possessed a lower activity than the rhodium counterparts. With diazoalkanes other than Ph 2CN 2, the activity of the supported catalyst B1 was partly higher and partly lower than that of complex 1 in the homogeneous phase. 相似文献
6.
Exposure of a dilute solution of SiCl 4 in adamantane to 60Co γ-rays at 77 K gave anisotropic ESR features which are shown to be characteristic of SiCl −4 anions with a trigonal bipyramidal structure. 相似文献
7.
Medium-resolution spectra of the N 2 b 1Π u-X 1Σ g+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Π u state: Δν 0 = 0.50 ± 0.05 cm −1, Δν 1 = 0.28 ± 0.02 cm −1, Δν 2 = 0.65 ± 0.06 cm −1, Δν 3 = 3.2 ± 0.5 cm −1, Δν 4 = 0.60 ± 0.07 cm −1, and Δν 5 = 0.28 ± 0.02 cm −1. From these linewidths, predissociation lifetimes τ ν were obtained: τ 0 = 16 ± 3 ps, τ 1 > 150 ps, τ 2 = 10 ± 2 ps, τ 3 = 1.6 ± 0.3 ps, τ 4 = 9 ± 2 ps, and τ 5 > 150 ps. Band origins and rotational constants for the b 1Π uν = 0 and 1 levels were determined for the 14N 2 and 14N 15N molecules. 相似文献
8.
Inner- and valence-shell electron energy loss spectra of gaseous SF 6, SeF 6 and TeF 6 have been measured at high impact energy (2.0–3.7 keV) and zero degree scattering angle. The resulting inner-shell excitation spectra include F 1s, S 2s and 2p in SF 6: F 1s, Se 3s, 3p and 3d in SeF 6 and F 1s, Te 4s, 4p, 4d and 3d in TeF 6. The results for each of these hexafluorides are interpreted, in the framework of the potential barrier model, as excitations to resonances involving a common manifold of virtual valence (inner-well) orbitals and also to Rydberg (outer-well) orbitals. The below-edge shape resonances in corresponding inner-shell excitation spectra of these hexafluorides show very similar variations in intensities in accord with expectations based on electric-dipole selection rules. This is an indication that these below-edge resonances in SeF 6 and TeF 6 are of the same symmetry as those in SF 6 (i.e. a 1g and t 1u). The continuum (above-edge) shape resonances in SeF 6 also show similar spectral behavior to those of SF 6 and can be understood by including Se 4d and S 3d orbitals in the basis for the respective MO schemes. However, in TeF 6 completely different spectral behavior is observed for the continuum resonances. In particular, there is a dramatic series of intense resonances observed above the Te 3d and 4d edges. The TeF 6 spectrum can only be understood by extending the MO basis set to include the Te 4f orbitals which are even lower lying than the Te 5d orbitals. Therefore, these continuum resonances which are also seen in the F 1 s and Te 3p spectra of TeF 6 are assigned to l=3 (f-type) continuum shape resonances due to involvement of the 4f orbitals rather than the l=2 (d-type) continuum resonances observed in SF 6 and SeF 6. This is the first reported observation of such f-type continuum shape resonances and such considerations will likely prove to be important in the understanding of near-edge spectra of heavy atom containing species. The VSEELS spectra which are very similar for the three hexafluorides also show significant continuum shape resonances. A consideration of both the ISEELS and the VSEELS spectra indicates that there is a weakening of the potential barrier in going through the series from SF 6, SeF 6 to TeF 6. 相似文献
9.
New efficient routes to the generation of silanones at relatively low temperatures are based on the following reactions: 1. (1) reaction of linear and branched perhydrocarbyldisiloxanes and oligosiloxanes, and of some of their C-functional derivatives, with gallium or indium iodides or bromides; 2. (2) reaction of hydrocarbylchlorosilanes R4−nSiCln (n = 2–4) and SiCl4 with dimethylsulphoxide (with or without Mg or Zn); 3. (3) Autodecomposition of organosilicon compounds containing
and
groups; 4. (4) reaction of R4−nSiCln with metal oxides of high redox potential (with or without the presence of CH3CN).
Insertions of dialkylsilanones into Si---O---Si and Si---O---C linkages as well as into the Si---Cl bond have been studied. 相似文献
10.
Effective homo-metathesis of a series of dichloro-substituted vinylsilanes H 2C = C(H)SiCl 2R (where R = Me, OSiMe 3, C 6H 5, C 6H 4–Me-4, C 6H 4–CF 3-4) in the presence of second generation Grubbs catalyst [Cl 2(PCy 3)(IMesH 2)Ru(=CHPh)] (I) and Hoveyda–Grubbs catalyst (II) leads to selective formation of E-1,2-bis(silyl)ethenes and ethene. On the basis of the results of experiments with deuterium-labelled reagents, a metallacarbene mechanism has been suggested for these reactions. 相似文献
11.
Valence and core ionization energies for the molecules SiH 4, H 3SiCl and H 3CCl have been obtained from RHF-SCF and PNO-CEPA wavefunctions. The calculated vertical ionization energies IE nv( n = 1, 2, 3) agree within about 0.2 eV with the PE spectroscopically determined values for SiH 4, H 3SiCl and H 3CCl. The increase in IE 1v for H 3SiCl relative to H 3CCl, which has been previously ascribed to a different d-orbital participation in the two molecules, is already reproduced by calculations with (s, p) basis sets. The ΔSCF method has been used to predict several core ionization energies. In addition, relative intensities calculated for the ionizations into the 2A 1 states of SiH 46 are compared with available experimental data, and some spectroscopic constants for SiH 4 and its ionic states are predicted. 相似文献
12.
The 1H and 13C NMR spectra of acetylserine, acetylphosphoserine and acetylphosphothreonine have been measured and completely analysed as a function of pD. For pD> 4 the NMR parameters are only slightly pD dependent. The second titration step of the phosphate group (pK 2 = 6.5) is much more difficult to detect in AcPSer (AcPTher) than in PSer (PThr). The ionization of the phosphate is of minor direct influence on the NMR parameters, their comparatively much larger changes in PSer (PThr) are due to conformational changes caused by the electrostatic interaction between the amino and phosphate group. The conformation in which the atoms H-C-Cβ-O-P form a planar W-type arrangement predominates at all pD values in the studied region from 4 to 14 in contrast to the non-cetylated phosphoamino acids in which its percentage passes a minimum at pD 8. 相似文献
13.
The vibrationally resolved mass analyzed threshold ionization (MATI) spectra of jet-cooled 7-azaindole have been recorded by ionizing via four different intermediate levels. The adiabatic ionization energy of this molecule is determined to be 65 462±5 cm −1, which is greater than that of indole by 2871 cm −1. The vibrational spectra of 7-azaindole in the S 1 and D 0 states have been successfully assigned by comparing the measured frequencies with those of indole as well as the predicted values from the ab initio calculations. Detailed analysis on the MATI spectra shows that the structure of the cation is somewhat different from that of this species in the neutral S 1 state. 相似文献
14.
研究了黄豆黄素和黄豆黄苷在不同pH条件下的吸收光谱和荧光光谱, 从分子结构的角度解释了二者呈现不同光谱特征的原因. 黄豆黄素分子基本无荧光. 在弱碱性时, 黄豆黄素分子发生7-OH质子的电离, 导致吸收光谱中320 nm的吸收峰红移至348 nm. 采用pH-光度法测得7-OH质子的电离常数p Ka1=7.08±0.04. 黄豆黄素一价阴离子呈现较强荧光, 最大激发和发射波长 λex/ λem分别为334 nm/464 nm, 荧光量子产率为0.049. 在碱性溶液中, 黄豆黄素4'-OH质子电离, 导致吸收光谱中254 nm的吸收峰红移至260 nm, 电离常数p Ka2=9.96±0.01. 黄豆黄苷分子基本无荧光. 在碱性条件下, 黄豆黄苷分子的4'-OH质子发生电离, 导致吸收光谱中256 nm的吸收峰红移至 280 nm, 电离常数p Ka=9.81±0.03. 黄豆黄苷阴离子基本无荧光, 但在热碱性条件下发生 γ-吡喃酮环裂解反应而产生较强荧光, λex/ λem为288 nm/388 nm, 裂解产物的荧光量子产率为0.056. 虽然, 黄豆黄苷与黄豆黄素是苷与苷元的关系, 但黄豆黄苷不能在热碱性条件下通过糖苷水解转变为黄豆黄素, 二者的荧光增强机理存在本质不同. 相似文献
15.
When 2-chloro-1,1,1,3,3,3-hexaphenyltrisilane is treated with an excess of HCl in a stainless steel autoclave, two phenyl groups per silicon atom are substituted by Cl yielding 1,1,2,3,3-pentachloro-1,3-diphenyltrisilane. All phenyl groups are replaced upon treatment with HCl/AlCl 3 in benzene solution. Coupling of the resulting trisilanes with ( tBu) 2Hg leads to branched hexasilanes (XCl 2Si) 2SiClSiCl(SiCl 2X) 2 (X = Ph, H), which are converted to the corresponding silicon hydrides by LiAlH 4. From the reaction of 1,4-diphenyl-2,3-bis(phenylsilyl)tetrasilane with HCl or HBr the tetrahalohexasilanes (ClH 2Si) 2SiHSiH(SiH 2Cl) 2 and (BrH 2Si) 2SiHSiH(SiH 2Br) 2 can be obtained. 相似文献
16.
合成了2个新配体4-(4-硫代乙酸)甲苯基-6-苯基-2,2'-联吡啶HC^N^N(PhCH 2SCOCH 3)(L3)和6-(4-硫代乙酸)甲苯基-2,2'-联吡啶 HC^N^N (CH 2SCOCH 3)(L5)及其发光的铂(Ⅱ)配合物ClPtC^N^N(PhCH 2SCOCH 3)(C3)和ClPtC^N^N(CH 2SCOCH 3)(C5). 通过 1H NMR谱和质谱对它们的结构进行了表征, 采用X射线单晶衍射分析确定了C3的晶体结构. 利用紫外-可见吸收光谱、 发射光谱及激发态寿命测定研究了它们的光物理性质和电化学性质, 以及配合物作为光敏剂在光催化制氢中的应用. 通过系列配合物产氢效率的比较, 揭示了它们的产氢效率和激发态寿命的关系. 相似文献
17.
The orbital relaxation energy is defined for single and double ionizations of valence electrons, and is calculated for CH 4, NH 3, H 2O and HF molecules with the ab initio SCF method. It is shown that the orbital relaxation energy for the ionization from a bonding orbital is about half of that for a non-bonding orbital, and the orbital relaxation energy for the double ionization is about double of that for the single ionization. This result gives a theoretical foundation for the empirical method of interpret Auger electron spectra by using experimental single ionization potentials. 相似文献
18.
Protonated acetaldehyde is methylated on the oxygen during interaction with methanol in the gas phase. The ionic product of the ion/molecule reaction between methanol and protonated acetaldehyde is identical with C-protonated methylvinyl ether (high-pressure ionization), and with the (M − C 2H 5) + fragment ion of sec-butyl methyl ether (following electron ionization), and also with the (M − OCH 3) + fragment ion of acetaldehyde dimethylacetal (following electron ionization). The structures of these ions and the mechanism of their formation were established by isotope-labeling experiments and collision-induced dissociation mass spectra of model compounds obtained with three different types of tandem mass spectrometers (BEQQ, triple-quadrupole, and a penta-quadrupole instrument). Gas phase synthesis of the product ion from [ 2H 3]-methanol or [ 2H 4]-acetaldehyde provided insight into its mode of formation and collision-induced dissociation. 相似文献
19.
利用共振双光子电离( R2PI)技术和质量分辨阈值电离(MATI)技术来研究2, 5-二氟苯酚分子。实验所测得的顺式、反式2, 5-二氟苯酚分子电子激发能 E1分别为36448和36743 cm -1,绝热电离能分别为71164和71476 cm -1。这两个顺反转动同素异构分子在电子激发 S1态与离子 D0态活性振动主要是由于面内环变形和与取代基相关的弯曲振动。分析2, 5-二氟苯酚分子的振动光谱、 D0态离子光谱以及理论计算均表明这两个转动异构体在 D0态的几何构型与 S1态的中性几何构型相当相似。 相似文献
20.
Fe-immobilized polyelectrolyte microshells have been successfully constructed by alternative adsorption of Fe(III) and alginate sodium (ALG) onto the precursor shells composed of chitosan (CHI) and ALG templated on melamine formaldehyde (MF) particles. Confocal laser scanning microscopy (CLSM) directly demonstrated that the as-synthesized (ALG/CHI) 4(ALG/Fe) n ( n = 1, 2) shells could accumulate efficiently rhodamine B (RhB), methylene blue (MB) and acridine orange (AO) in well-defined internal space under moderate conditions via a simple mix processing. Further, H 2O 2 could cross the Fe-immobilized shell walls and react with the dyes concentrated in the interior of shells under visible radiation. The photodegradation of dyes accumulated in the microshells in the presence of H 2O 2 was characterized by UV–vis adsorption spectra and CLSM. More importantly, the photooxidative reaction occurring in the Fe-immobilized microshells can be performed at a wide range of pH from acid to neutral media, which is superior to the conventional Fenton reaction that allows taking effect only under acid condition of pH <4. Electron paramagnetic resonance (EPR) and other studies into the mechanism of the light-activated reaction process give tentative evidence that distinct from the photoreaction occurring in neutral medium, the photoreaction taking place in confined microshells in acid medium proceeds mainly through HO radicals with high oxidative potential. 相似文献
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