Planar Symmetrical XY3 and Boron Trihalides: Mean-Square Amplitudes and Keating Coordinates

The E' block of the mean-square amplitude matrix (Σ) for the planar symmetrical XY₃ molecular model is treated theoretically in terms of the Keating coordinates. A numerical example for ¹¹BF₃ is given. Also the mean amplitudes of vibration (ι) and Bastiansen-Morino shrinkage effect (Δ) are considered. New relations which connect the mean-square amplitudes and force constants are given. Previous works on mean amplitudes and related quantities for boron trihalides from vibrational spectroscopy and gas electron diffraction are reviewed, and some new calculations are reported.     

Synthesis of 6‐Bromocoumarins Using Tetrabutylammonium Tribromide as a Selective Brominating Agent and an Efficient Generator of HBr

A simple and efficient one‐pot synthesis of 6‐bromocoumarins was achieved in good yields via the three‐component reaction of phenols, 4‐substituted acetoacetate and tetrabutylammonium tribromide (TBATB) in CH₂Cl₂‐MeOH.     

高分子载体Lewis酸催化剂:聚苯乙烯-三溴化硼复合物——Ⅰ.制备及其在有机合成中的应用

用交联聚苯乙烯白球与三溴化硼反应制成了一种十分稳定的复合物,其中含溴1.99%,相当于每克复合物小球含7.91×10~(-5)mol BBr_3。它对缩醛、缩酮、酯化等有机合成反应有较好的催化效能,还可重复使用,是一种制备简单、使用方便的新型高分子载体 Lewis 酸多相催化剂。     

三溴甲基芳烃合成新方法的研究

报道了一种以三氯甲基芳烃与三溴化硼反应制备系列三溴甲基芳烃的新方法. 该方法反应条件温和, 收率高, 选择性好. 同时, 对影响该反应的因素进行了研究, 发现当芳环上连有强吸电子基团时, 不利于反应的进行, 而连有推电子基团时, 则有利于反应进行; 当取代基处于邻位时, 则明显阻碍反应的进行. 采用这种方法已合成了十多个三溴甲基芳烃, 其中1个是未见文献报道的新化合物.     

新型高选择性芳环溴化剂

苄基三甲基三溴化铵是新型高选择性的芳环溴化剂。在ＣＨ２Ｃｌ２－ＣＨ３ＯＨ或ＣＨ３ＣＯＯＯＨ－ＺｎＣｌ２中，它与酚，芳胺，酰胺，芳醚，芳烃及芳杂环化合物等反应，选择性得到对应的单，双或三溴化产物。     

CsBr与SmBr3在氢溴酸介质中反应的相化学

由于稀碱稀土卤化物特殊的材料性能，正日益受到各国科学家的关注［‘－3］．动年代初，M：y：：提出了下述4种类型卤化物A’RE？X7（1：2型）、AIREyXgta：2型）、AIRE”X6ta：l型）及AgRE”X。（2：l型）的合成方法（A为碱金属）分析Meyer等人的合成方法网；发现其初始反应是     

Molecular structure and force field of boron tribromide as determined from combined analysis of gas electron diffraction and spectroscopic data and supported by quantum-chemical density-functional calculations

The thermal-average parameters of BBr₃ at 21(1) °C were obtained from a conventional analysis of gas electron diffraction (GED) data (r_g(B---Br) = 190.0(4) pm). The equilibrium structure and the force constants were refined from a joint analysis of the GED intensities and vibrational frequencies using different approximations. The simplest approximation (quadratic potential function in rectilinear coordinates) is suitable for the refinements of the equilibrium bond length (r^h_e(B---Br) = 189.6(4) pm) and the force constants of BBr₃. The molecule is planar within the error limits. Quantum-chemical density-functional calculations supported planarity of the molecule.     

Synthesis and Crystal Structure of Potassium Indium Tribromide,KInBr3

KInBr₃, the first ternary indium bromide containing divalent indium, is synthesized from InBr₃, KBr, and elemental In at 450 °C. Its trigonal crystal structure (a = b = 853.24(1) pm, c = 1077.76(2) pm; P3¯; Z = 4) has been solved and refined from X-ray powder data. Indium atoms of oxidation state two are found in an [In₂Br₆]^2– unit with ecliptic ethane structure while potassium ions are located in two different polyhedra. There is an octahedral coordination by bromine anions for half of the K⁺ whereas the other K⁺ cations are located in trigonal Br^– prisms, tricapped by three additional Br^– anions.     

碱金属和稀土溴化物Meyer反应的相化学研究(Ⅰ)──四元体系CsBr-LaBr3-HBr(12％)-H2O(25℃)的研究

研究了四元体系CsBr-LaBr₃-HBr(12%)-H₂O(25℃)的相化学关系,绘制了相应的溶度图。在该体系中发现一种新型化合物5CsBr·2LaBr₃·22H₂O;对该化合物进行了偏光、X射线粉末衍射、TG及DTA等方面的测定。将本体系与四元系CsCl-LaCl₃-HCl(13%)-H₂O(25℃)相比较,发现两者在生成化合物的数量、种类和相化学行为方面均有较大的差异。     

Synthesis and Application of Poly(diallyldimethylammonium tribromide)as a Novel Polymeric Brominating Agent

In this study, the synthesis and applications of a new supported tribromide reagent based on poly(diallyldimethylammonium chloride) is reported. This supported tribromide is used in α‐bromoacetalization of ketones, bromination of alkenes and regioselective bromination of activated aromatic compounds. This method is mild and no Br₂ and HBr were used. Other advantages of this reagent are stability, high efficiency, simple filtera‐ bility and reusability.