DFT Studies on the addition reaction between germylene and furan

The mechanism of the addition reaction of germylene H₂Ge and furan has been investigated with B3LYP/6-311+G* method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. From the surface energy profile, it can be predicted that there are four reactions (1)–(4). Reactions (1) and (2) are similar, which are reactions between H₂Ge and C=C of isolated furan. Furthermore, H₂Ge can react with oxygen atom of furan to form a stable complex H₂Ge-Furan. Reactions (3) and (4) are similar, which are reactions between H₂Ge and C=C of the complex H₂Ge-Furan. All the reactions consist of two steps: the two reactants first form an intermediate (INT) through a barrier-free exothermic reaction; this intermediate then isomerizes to a product (P) via a transition state (TS). The article is published in the original.     

A theoretical study on the mechanism of the addition reaction between carbene and epoxyethane

The mechanism of addition reaction between carbene and epoxyethane has been investigated employing the MP2 and B3LYP/6-311+G* levels of theory. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Based on the calculated results at the MP2/6-311+G* level of theory, it can be predicted that there are two reaction mechanisms (1) and (2). In the first reaction carbene attacks the atom O of epoxyethane to form an intermediate 1a (IM1a), which is a barrier-free exothermic reaction. Then, IM1a can isomerize to IM1b via a transition state 1a (TS1a), where the potential barrier is 48.6 kJ/mol. Subsequently, IM1b isomerizes to a product epoxypropane (Pro1) via TS1b with a potential barrier of 14.2 kJ/mol. In the second carbene attacks the atom C of epoxyethane firstly to form IM2 via TS2a. Then IM2 isomerizes to a product allyl alcohol (Pro2) via TS2b with a potential barrier of 101.6 kJ/mol. Correspondingly, the reaction energies for the reactions (1) and (2) are −448.4 and −501.6 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate. The results based on the B3LYP/6-311+G* level of theory are paralleled to those on the MP2/6-311+G* level of theory. Furthermore, the halogen and methyl substituent effects of H₂C: on the two reaction mechanisms have been investigated. The calculated results indicate that the introductions of halogen or methyl make the addition reaction difficult to proceed.     

Effect of reaction temperature on intercalation of octyltrimethylammonium chloride into kaolinite

The structural property, thermal behavior, and morphology of octyltrimethylammonium chloride–kaolinite complexes prepared at different reaction temperatures were studied by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry–differential scanning calorimetry, and scanning electron microscope. The present study demonstrated that the arrangement model of octyltrimethylammonium cations (OTAC⁺) within the kaolinite interlayer space was independent of reaction temperature. The alkyl chains adopted a similar rigid paraffin-bilayer arrangement with different tilted angles. Although the intercalation led to an increased number of gauche conformers, the number of nonlinear conformers remained constant with increasing temperature. With increasing temperature, the number of trans conformers continuously augmented and resulted in decreased gauche/trans ratio. Therefore, the molecular environment remained solid like. Simultaneously, the surfactant packing density gradually increased, along with the decreasing water content in the organoclays. This effect improved thermal stability and hydrophobicity. The thermal decomposition processes of the kaolinite–OTAC⁺ complex can be divided into four steps. Furthermore, SEM images showed that the morphology of these complexes was strongly dependent on the given temperature. In general, increasing the temperature within the limited given temperature (≤70 °C) promoted the transformation from platy layers to nanoscrolls. Most of the transformed nanoscrolls were acquired in the products prepared at 70 °C, and further increasing in temperature decreased the nanoscrolls yield. Nevertheless, the packing density increased in the process, thereby demonstrating that the packing density not only promoted nanoscrolls transformation but also prevented the progress.

     

肼黄与牛血清白蛋白相互作用的光谱研究

本文用荧光光谱法和紫外-可见吸收光谱法研究了肼黄与牛血清白蛋白(BSA)结合反应的光谱行为,发现肼黄因对BSA有较强的荧光猝灭作用,且肼黄的紫外吸收光谱和BSA的荧光发射光谱有一定程度的重叠,据此得出了其结合反应的结合常数、结合位点数和基本热力学参数等,并研究了二者的相互作用机理。     

The mechanochemical reactions between CsF and kaolinite

The grinding of a mixture containing kaolinite and CsF was carried out by three different techniques, short manual grinding, Fisher mechanical mortar and Retsch ball mill. In addition to different cesium aluminium silicates which were detected by X-ray powder diffraction, a new type of intercalation complex was identified by FTIR spectroscopy. The X-ray diffractogram of this complex did not show any basal spacing, which may characterize the complex but the 0.715 nm characteristic peak of the untreated kaolinite became very weak. The Retsch ball mill led to a slight destruction of the kaolinite and the formation of small amounts of the new intercalation complex. The delamination of book-like kaolinite assemblages was observed after the manual and Fisher mortar grindings. In the latter grinding techniques the kaolin-like layers persisted and served as the framework for the intercalation complexes. Received: 4 February 1998 Accepted: 11 March 1998     

Kinetics of addition and allyl-hydrogen abstraction in the reaction between methyl radicals and 1-heptene

The rates for reactions between methyl radicals and 1-heptene have been studied and the kinetic parameters log (k₁/dm³ mol^–1s^–1)=8.4±0.1–(33.3±1.0) kJ/RT In 10 and log (k₃/dm³ mol^–1s^–1)=7.5±0.2)–29.7±1.5) kJ/RT In 10 have been determined for addition and allyl-hydrogen abstraction, respectively.

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1- log (k₁/^{3 –1 –1})=(8,4±0,1)-(33,3±1,0) kJ/RT In 10 log (k₃/^{3 –1 –1})=(7,5±0,2)–(29,7±15) kJ/RT In 10 .

     

High melting thermoplastic/epoxy resin blends: Influence of the curing reaction on the crystallization and melting behavior

The influence of the cure process and the resulting reaction‐induced phase separation (RIPS) on the crystallization and melting behavior of polyoxymethylene (POM) in epoxy resin diglycidylether of bisphenol A (DGEBA) blends has been studied at different cure temperatures (180 and 145 °C). The crystallization and melting behavior of POM was studied with DSC and the simultaneous blend morphology changes were studied using OM. At first, the influence of the epoxy monomer on the dynamically crystallized POM was investigated. Secondly, a cure temperature above the melting point of POM (T_cure = 180 °C) was applied for blends with curing agent to study the influence of resulting phase morphology types on the crystallization behavior of POM in the epoxy blends. Large differences between particle/matrix and phase‐inverted structures have been observed. Thirdly, the cure temperature was lowered below the melting temperature of POM, inducing isothermal crystallization prior to RIPS. As a consequence, a distinction was made between dynamically and isothermally crystallized POM. Concerning the dynamically crystallized material, a clear difference could be made between the material crystallized in the homogeneous sample and that crystallized in the phase‐separated structures. The isothermally crystallized POM was to a large extent influenced by the conversion degree of the epoxy resin. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2456–2469, 2007     

高岭石与水分子相互作用的理论研究

为从微观角度深入探讨单个水分子与高岭石最易解理晶面不同暴露末端的作用特点,本工作通过密度泛函理论的计算方法对不同吸附形态的水分子与不同暴露末端的稳定作用构型进行几何结构与电子结构分析.吸附能的计算结果表明水分子在铝氧八面体羟基作为暴露末端的表面上最稳定的吸附方式为水分子的氧原子和氢原子分别与相邻两个羟基的氢原子和氧原子...     

Relation between aggregation kinetics and the structure of kaolinite aggregates

Dynamic and static light scattering were applied to the determination of the stability ratio and fractal dimension of kaolinite (KGa-2) at different kaolinite or/and electrolyte concentrations at pH 9.5. Dynamic light scattering was used to measure the kinetics of early stage aggregation to determine the stability ratio, W, as well as the cluster sizes which determine the fractal regime. Static light scattering was used to measure the fractal dimension, D(f). Results show that the two classes of "universality" (Lin et al. Nature 1989, 339, 360) characterizing the diffusion- and reaction-limited regimes of cluster-cluster aggregation do apply to colloidal kaolinite as limit cases when W approximately 1 or W > 100, respectively. In the intermediate regime where 5 < W < 100, the growth of the aggregate radius showed a power-law behavior similar to diffusion-limited cluster aggregation. For the intermediate aggregation regime, a scaling relation between fractal dimension and stability ratio, reflecting a continuous increase in particle packing density in the aggregate as the sticking probability of particles was reduced, was demonstrated.     

Quantum-chemical investigation into the geometric and energetic characteristics of kaolinite cluster models

A method of constructing molecular models for layered aluminosilicate crystals is put forward. The geometric and energetic characteristics of cluster models are calculated for the elementary kaolinite crystal layer using the MNDO approximation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 3, pp. 214–218, May–June, 1993.     

Photochemical control of a highly efficient addition reaction between electron-rich alkynes and tetracyanoethylene

The electron density of an alkyne moiety is enhanced by the photochromic ring closure of a diarylethene derivative, which allows the thermal addition reaction with a small π-acceptor, tetracyanoethylene, at room temperature.     

灰中焦对煤灰熔融特性的影响

采用连有电脑－摄像头的煤灰熔融特性测定装置，在Ar气氛下研究了灰中焦对煤灰熔融特性的影响。结果表明，灰中焦对灰熔融特征温度和灰熔融动态特征具有显著影响，影响程度与煤种以及煤焦的质量分数有关。掺焦的灰熔融温度高于不掺焦的熔融温度；掺焦量增加，其灰熔融温度升高。当掺焦量提高至20%时，在接近或高于煤灰熔融温度时由于焦与焦之间通过熔融煤灰的黏结作用形成了不熔骨架，使灰锥高度不再随温度的提高而发生变化，这也是灰锥很难出现或者根本不出现软化温度和流动温度的原因。     

Addition reaction of halogens to vinyl(pentafluorocyclopropanes): competition between a radical addition and an electrophilic addition

Vinylpentafluorocyclopropanes 1 react with I(2) to give the (Z)-1,5-adduct 2, whereas 1 reacts with Cl(2), Br(2) or I-Cl to produce (Z)-1,5-adduct 3 predominantly along with small amounts of 1,2-adduct 4, which are formed by a radical mechanism and an ionic mechanism, respectively.     

Topics on the preparation of HTSC via solid state reaction and melting process

The problems of the preparation of High Temperature Superconductors by sintering and melting are examined. Results of the thermal properties of the total substitution of Yttrium by a rare earth element are reported. The process of fabrication of HTSC after high temperature decomposition is indicated. The results of first characterisation are also reported.

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Zusammenfassung Probleme der Herstellung von Hochtemperatur-Supraleitern durch Sinter- und SchmelzvorgÄnge wurden untersucht.Es werden Resultate der thermischen Auswirkungen der vollstÄndigen Substitution von Yttrium durch Seltenerdelemente wiedergegeben. Der Prozess einer Herstellung von HT-Supraleitern nach thermischer Zersetzung im Bereich hoher Temperatur wird beschrieben, und es werden Resultate erster Charakterisierungen mitgeteilt.

     

Correlation between acoustic cavitation noise and yield enhancement of sonochemical reaction by particle addition

The mechanism of the effect of particle addition on sonochemical reaction is studied through the measurements of frequency spectrum of sound intensity for evaluating the cavitation noise and the absorbance for the liberation of iodine from an aqueous solution of KI as an index of oxidation reaction by ultrasonic irradiation in the presence or absence of alumina particles. As it is expected that both the acoustic noise and a rise in temperature in the liquid irradiated by intense ultrasound will increase with the number of collapsing bubbles, these are supposed to be the best tools for evaluating the relative number of bubbles. In the present investigation, it has been shown that the addition of particles with appropriate amount and size results in an increase in the absorbance when both the acoustic noise and the rise in the liquid temperature due to cavitation bubbles also increase. This suggests that the enhancement in the yield of sonochemical reaction by appropriate particle addition comes from an increase in the number of cavitation bubbles. The existence of particle in liquid provides a nucleation site for cavitation bubble due to its surface roughness, leading to the decrease in the cavitation threshold responsible for the increase in the number of bubbles when the liquid is irradiated by ultrasound. Thus, from the present investigation, it is clarified that the particle addition has a potential to enhance the yield in the sonochemical reaction.     

Effects of mechanical activation on the non-isothermal kinetics of mullite formation from kaolinite

The non-isothermal kinetics of mullite formation from both non-activated and mechanically activated kaolinite have been studied by differential thermal analysis (DTA). Kaolinite was mechanically activated in a planetary mill, while amorphization in the structure was studied by X-ray diffraction analysis. It was established that the mechanical activation especially affected the loss of structural water. The activation energies depending on the conversion for mullite formation have been calculated from the DTA curves by using the non-isothermal method of Coats and Redfern at heating rates of 5, 10, 15, and 20 °C min⁻¹. The mechanical activation and amorphization of the kaolinite brings to the formation of mullite at a lower heating temperature.     

Catalysts for heterogeneous oxidation reaction based on metalloporphyrins immobilized on kaolinite modified with triethanolamine

Raw kaolinite was modified with triethanolamine (TEA), in an attempt to create a new support for the immobilization of metalloporphyrins. Anionic metalloporphyrins containing Fe(3+) or Mn(3+) as metallic centers were immobilized on the prepared support, and the obtained solids were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), thermal analysis (thermogravimetric and differential thermal analyses--TGA/DTA), and scanning electron microscopy (SEM). The solids were used in heterogeneous oxidation catalysis of cyclooctene and cyclohexane. The yields from the oxidation of cyclooctene depended on the amount of TEA and/or water present in the solids. Good reaction yields were obtained for the oxidation of cyclohexane, with selectivity for the alcohol. In one specific case, a possible co-catalytic activity was verified for TEA during the oxidation of cyclohexane.