Diborane (4) derivatives via coupling of amine monobromocyanoboranes: Study of the bromination of amine cyanoborane and molecular structures of the amine dibromocyanoboranes

The first examples of diborane (4) compounds derived from amine cyanoboranes are described. A series of monobromo derivatives of amine cyanoboranes (A:BHBrCN), and dibromo derivatives (A:BBr₂CN), 1-7, were prepared. Lithiation of the monobromo derivative of trimethylamine cyanoborane, using n-BuLi, did not produce the C-lithiated intermediate Li⁺ [CH₂NMe₂BHBrCN]⁻, but instead the B-lithiated intermediate Li⁺ [Me₃NBHCN]⁻, was obtained. This intermediate, when allowed to react for 16 h, coupled with the un-lithiated trimethylamine monobromocyanoborane (Me₃NBHBrCN) and resulted in diborane (4) derivative formation as the 2LiBr complex. The same result was obtained when one equiv of the trimethylamine monobromocyanoborane was added to the reaction mixture 1 h after lithiation. Following the same procedure, novel diborane (4) derivatives of amine cyanoboranes were successfully obtained, 8-11, as their 2LiBr complexes from the monobromo derivatives of the corresponding amine cyanoboranes. Molecular structures of the trimethylamine dibromocyanoborane, 6, and the triethylamine dibromocyanoborane, 7, were determined using X-ray crystallography.     

富烯碳原子簇的石墨层间闭合形成机理

本文提出了富烯碳原子簇的石墨层间闭合形成机理，由该机理推出的许多结果与实验事实符合很好。我们认为碳原子簇自由基的快速淬灭及其淬灭速度是富烯碳原子簇形成及其丰度的决定因素。由此得出富烯碳原子簇在给定实验条件下产生的必然性，并预言不同大小的富烯碳原子簇可以通过优化实验条件选择性地合成。     

Anomalous hydroalumination of methyl nopol ether with a LiAlH4-3AlBr3 system

Hydroalumination of methyl nopol ether with a LiAlH₄-3AlBr₃ system is accompanied by a skeleton rearrangement and gives 6-dibromoalumo-7-methoxymethyl-2-menthene. Further hydroalumination affords a mixture of 2,6- and 2,5-bis(dibromoalumo)-7-(methoxymethyl)menthanes in 8020 ratio. Hydrolysis and oxidation of these organoaluminum compounds were carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 506–510, March, 1994.     

An Electrostatic Bond Energy Model for Enthalpies of Formation of Chloroalkanes in Gaseous States

An electrostatic bond energy model is formulated to fit the enthalpies of formation and dipole moments of the alkanes and chloroalkanes. In this model, the charge distributions are calculated by an electrostatic approach similar to the "MSE" method, and the enthalpy of formation of a molecule is the sum of the bond energy terms plus the electrostatic energy of the interactions between the charges on all atoms. All parameters of this model are obtained by parameterization. The calculated dipole moments for 13 chloroalkanes and enthalpies of formation for 19 alkanes and non-geminal chloroalkanes agree with the determined values very well. To calculate the enthalpies of formation of geminal chloroalkanes, a correction mainly attributed to the van der Waals interactions in the geminal substituted group, about 24 kJ/mol per pair of geminal chlorine atoms, is introduced.     

用动力学方法研究8,9-苯并-2-亚甲基-1,4,6-三氧螺[4,4]壬烷的聚合反应机理

根据在自由基引发剂存在下,8,9-苯并-2-亚甲基-1,4,6-三氧螺(4,4)壬烷(Ⅰ)可能存在的竞争反应,推导了动力学方程式。用红外光谱法测定了单体的消失速率和苯酞的生成速率。实验结果与推导动力学方程式相符。进一步证明了单体(Ⅰ)的增长反应由加成聚合和开环—异构化—加成这两个反应组成。这两个反应对总速率的相对贡献与单体浓度有关。得到了共聚物的结构。     

Controlled Rate Thermal Analysis of Hydrated Borates

Quasi-isothermal-isobaric analysis was applied as a main method for investigation of thermal decomposition of borates. The structural mechanism of the dehydration and dehydroxylation of selected borates is considered. It has been found that they consist of two independent stages: formation of gaseous water molecules localized into the structural framework and their release. The internal pressure of gaseous water molecules is the factor influencing the course of these processes. The strengths of the chemical bonds of the components and the freedom of their displacement also determine thermal stability of hydrated borates. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetic model ofCO oxidation on nonuniform surface analyzed regardingCOads spillover, 2. homotopic method. Effect ofm1 surface portion

The homotopic method has been used to analyze the kinetic model of three-stageCO oxidation on two nonuniform surface patches conjugated byCO ₂ spillover. Diagrams of steady states depending on the portion of surface patchm ₁ at various temperatures and pressure ratiosP(O ₂)/P(CO) have been constructed. The ratios of different type patches corresponding to the maximum overall reaction rate have been found.     

Plasma-chemical decomposition of methane during diamond synthesis

Using a mass spectrometric sampling method, we have observed the decomposition of CH₄ in an rf plasma usedfor diamond deposition. The gas samples were extracted through an orifice located downstream of the plasma zone and analyzed online. For the experiments a dilute mixture of H₂ and CH₄ containing 0.1–3% CH₄ has been used. CH₄ is converted to C₂H₂ and C₂H₄ quantitatively. Small amounts of heavier hydrocarbons are formed. A comparison of the experimental results with a recent kinetic model treating a purely thermal environment is made and the differences between our experiment and the model are explained. The role of acetylene as a species formed in an atmosphere rich in atomic hydrogen is proposed. The electron impact dissociation process is suggested as the rare-determining step in the plasma-chemical decomposition of methane.     

On the mechanism of solute retention in RP-HPLC systems with B+AB1+AB2 type eluents

Summary Intermolecular interactions between the solute and the moieties constituting the mobile phase significantly contribute to the overall retention pattern of a given solute in a given chromatographic system. In this paper retention of solute is discussed in the case of the B+AB₁+AB₂ type mobile phase, which, in a quasithermodynamic way, can be divided into seven individual moieties. One evaluates the influence of each moiety on solute retention, and refers these regularities to the polarity of the solutes.     

纳米分辨率的三维形貌检测仪

从光干涉方式，瞳窗关系和光源带宽等基本关系出发，利用空间不变系统理论解析了相移显微干涉检测系统中衍射效应的影响。为了减小横向分辨率对纵向分辨率的影响，利用相关信息提取或数字滤波的方法，获得了纳米分辨率的三维形貌。