溴代稠环芳烃的氧化溴化法合成

以HBr/H2O2为溴化体系,采用氧化溴化法合成了6种稠环芳烃的溴化物。 合成反应无需催化剂,通过控制反应温度和溴化试剂用量,可以在稠环芳烃化合物的活性位选择性地单溴化或双溴化,产率可达51.1%～94.2%。 产品经熔点和1H NMR法确认,合成操作简单安全,环境污染少,有工业应用前景。     

芳香化合物氧化溴化研究进展

芳香化合物的氧化溴化反应是合成芳香溴化物的重要方法之一.综述了近年来芳香化合物氧化溴化的研究进展,主要包括化学计量的氧化溴化和催化氧化溴化等部分,其中后者主要包括H2O2和O2作氧化剂的催化氧化溴化.     

聚吡唑硼酸盐钒氧配合物的合成及对苯酚红催化溴化活性

在室温溶液反应中设计合成了一个新的三聚-4碘代吡唑硼酸的钒氧配合物:[VO(C₆H₉O₂)(Tp^4I)]·2H₂O(Tp^4I=三聚-4-碘代吡唑硼酸盐)。 通过元素分析、红外光谱、紫外光谱、热重、X射线粉末和单晶衍射等技术手段对其结构进行了表征。 以苯酚红为底物,在过氧化氢的存在下,进行仿生催化溴化的研究。 结构分析表明,中心金属钒为6配位,与配位原子形成了一个八面体几何构型。 配体三聚4-碘吡唑硼酸盐(Tp^4I)采取三齿螯合配位模式。 在仿生催化溴化实验中,配合物对苯酚红的溴化氧化反应表现出良好的催化活性,催化该反应体系的反应速率常数达到k=2.826×10² (mol/L)^-2·s^-1。 同时将此反应体系应用于过氧化氢的检测。     

溴过氧化物酶催化环己烯环氧化反应

研究了分离自珊瑚藻(Corallina officinalis)的溴过氧化物酶在水-有机两相体系中催化环己烯环氧化的反应.考察了氧化剂种类与添加方式、pH、反应温度、酶浓度及KBr浓度等条件对环氧化反应的影响.最佳反应条件为:反应温度55℃,在含有50mmol/LKBr和32U/ml溴过氧化物酶的pH6.0的Tris-HCl缓冲液中,每隔10min补加50μl的2.29mol/LH2O2.在此反应条件下,环氧环己烷的收率达到41.5%,选择性为82.2%.     

过氧化氢氧化酸性铬兰K催化动力学光度法测定溴离子

在中性条件下,游离的Br-对H2O2氧化酸性铬兰K褪色反应具有催化作用。基于此建立了测定微量Br-的催化光度分析方法。结果表明,该方法最大吸收波长为525 nm,测定的线性范围为0.4μg/mL～11.2μg/mL,检出限为0.321μg/mL。方法用于河水中微量Br-的测定,结果令人满意     

负催化动力学光度法测定溴的研究

本文报道了溴 ( Br- )对溴酸钾氧化甲基橙 ( MO)褪色反应的负催化作用及其动力学分析 ,建立了测定痕量溴的新方法。方法的检出限达到 1 .0× 1 0 - 9g/ m L,线性范围 0 .5～ 1 .8ng/ m L,表观摩尔吸光系数 1 .0× 1 0 6 L·mol- 1·cm- 1。用于井水 ,精盐中痕量溴的测定 ,结果满意     

孔雀石绿-H_2O_2体系动力学光度法测定微量溴化物

基于在NH3-NH4Cl介质中, Br-对H2O2氧化孔雀石绿的褪色反应有催化作用的特性, 建立了高灵敏度测定痕量溴化物的催化动力学光度分析法新体系. 讨论了酸度、试剂用量、温度、干扰离子等因素的影响. 研究了反应的最佳条件, 测定了一些动力学参数, 非催化反应和催化反应的的表观活化能分别为为52.85和19.53 kJ/mol. 方法的线性范围为0.10～1.2 μg/mL Br-, 检出限为 0.081 μg/mL. 方法用于水样中溴化物的测定, 结果与国标分析法所得结果相吻合.     

碳水化合物衍生的手性配体——25含碳水化合物单元的膦配体在钯催化的Heck反应中的应用

评价了一种碳水化合物衍生的具有较大立体位阻及较三苯基膦更富电子的膦配体(甲基3-脱氧-3-二苯膦基-4,6-氧-苯次甲基-α-D-吡喃阿卓糖苷,3-MBPA)在Pd催化的Heck反应中的性能.发现在N,N-二甲基乙酰胺溶刺中K2CO3是该催化体系较适合的碱;在该配体的支持下催化剂中钯的用量可低至0.5 mo1%;可催化苯乙烯与带给电子基团的溴代芳烃及带吸电子基团的氯代芳烃发生反应,高产率地生成相应的偶联产物;反应区域选择性表明,Pd(OAc)2/3-MBPA体系在催化苯乙烯与卤代芳烃的Heck反心中并存阳离子催化途径,说明3-MBPA中的氧原了可能也参与配位;同时发现,加入助配体四丁基溴化胺(TBAB)后,可能是Br-参与配位有利于增加中性催化途径的机会而提高了反应区域选择性.     

烷基苯上α-H溴代反应的新方法

α-溴代烷基苯是一类很重要的有机合成中间体 ,传统方法以溴[1] 、NBS[2 ] 、CBr Cl3[3] 、Cu Br2 [4 ] 和Br- /Br2 [5] 等为溴化剂在加热或光照条件下进行 .为了得到满意的结果 ,通常须在比较激烈的条件下进行 ,如对硝基甲苯的溴化 ,反应温度为 1 45～1 50℃ ,收率仅 53 %～ 59%[6 ] .我们采用新的溴化剂应用于烷基苯上 α-H的溴化 ,通过与传统方法比较发现 ,该法具有工艺操作条件简单 ,污染少 ,选择性好和产品收率较高等特点 .应用于钝化烷基苯上 α-H的溴化 ,如对甲苯腈、对硝基甲苯等 ,结果令人满意 .化学反应通式如下 :R CH2 R1…     

(-)-龙脑手性离子液体的合成

以(-)-龙脑为手性源,与溴乙酰溴通过酯化反应合成溴代乙酸龙脑酯(2);2与4,4'-联吡啶发生取代反应引入两个手性中心制得新型手性离子液体——N,N'-双(龙脑氧甲酰亚甲基)联吡啶.二溴(3.2Br-);3.2Br-与四氟硼酸钾或六氟磷酸钾盐进行阴离子交换制得相应的手性离子液体3.2BF4-或3.PF6-.3.2Br...     

Anion and Cavity Effects on the Complexation Behavior of Di-Aza-Benzo-Crown-Ether Calix[4]arene towards Zn(II) Ions

A novel compound, 25, 27 - N,N - di - ((2 -ethoxy)benzyl)butylenediamine - p - tert- butylcalix[4]arene, 1, has beensynthesized by reducing its Schiff base derivative. Inclusion studies by¹H-NMR spectroscopy in a mixed solvent (CD₃OD/CDCl₃) of25,27-N,N-di-((2-ethoxy)benzyl)propylenediamine-p-tert-butylcalix[4]arene,2, and 1 with Zn(II) ions, where counter anions are Cl^-, Br^-, I^- and NO ₃ ^- ,show that both ligands can bind Zn(II) to a different extent depending onthe counter anions and the cavity size of the ligands. The stabilityconstants of ZnX₂–1 (ZnX₂-2) complexes where X = Cl^-, Br^-, I^- and NO ₃ ^- are 1.4 ± 0.1 (1.6 ± 0.1), 1.7 ± 0.1 (1.9 ±0.1), 2.2 ± 0.1 (2.7 ± 0.1) and 4.7 ± 0.1 (6.0 ±0.1), respectively. The calix[4]arene unit of the ligand 2 was found to havea structural change from cone to partial cone conformation upon binding toZnCl₂, ZnBr₂ and ZnI₂.     

A re-examination of the decay kinetics of pulse radiolytically generated Br-2 radicals in aqueous solution

The decay of Br^-₂ in Ar-purged or N₂O-saturated aqueous solutions of KBr (0.01-1.0 M) in the pH range 1–7 has been re-examined using the techniques of pulse radiolysis and computer simulation. The dependence of the rate constant for the intrinsic decay of Br^-₂ on ionic strength (controlled by KBr) has been established; the values of k (Br^-₂ + Br^-₂) are (1.9 ± 0.1) × 10⁹, (2.2 ± 0.3) × 10⁹ and (2.4 ± 0.3) × 10⁹ M^-1 s^-1 in the presence of 0.01, 0.1 and 1.0 M KBr, respectively, independent of pH between 2 and 7. The computer simulation of the decay of Br^-₂ has also generated, for the latter species, ϵ = 10,000 ± 700 M^-1 cm^-1 at λ_max = 360 nm; this value has been calculated without making any assumption concerning G(Br^-₂). For the reduction of Br^-₂ by H atoms, a value of k (H + Br^-₂) = (1.4 ± 0.3) × 10¹⁰ M^-1 s^-1 has been obtained in the presence of 0.01-1.0 M KBr, independent of pH between 1–4. For the reduction of Br^-₂ by e^-_aq at pH 7 (10^-3 M phosphates) and μ = 0.1, a value of k (Br^-₂ + e^-_aq = (1.1 ± 0.2) × 10¹⁰ M^-1 s^-1 has been obtained.     

Free Ḃr atom and free radical reactions in the radiolysis of 1,2-dibromoethane (DBE) and other bromohydrocarbons in air-free aqueous solutions

G(Br^-)-values have been evaluated in Ar- and N₂O-saturated 1,2-dibromoethane (DBE), bromobutane, propylbromide and bromopentane (BP) under a variety of experimental conditions in aqueous solutions. G(Br^-) increases with increasing halogenated hydrocarbon concentration and with increasing pH. Free Ḃr atoms formed as a result of e^-_aq and ȮH radical reactions with bromohydrocarbons are considered to initiate a chain reaction. Another chain reaction has been invoked to explain the high G(Br^-) at high pH. Ḃr radicals may form a reactive intermediate with OH^- (BrOH^⨪), which decays to Br^- and ȮH. The ȮH radicals have been found to interact with bromohydrocarbons and eventually yields Br^- ions. The formation of Br^- ions is accelerated both at acidic and alkaline pH in systems containing t-butanol. Dose rate studies in Ar- and N₂O-saturated 1,2-DBE and BP show an increase in G(Br^-)-values at low dose rate and confirm the occurrence of a chain reaction initiated by Ḃr atoms. From these studies the rate constant for the reaction of Ḃr with 1,2-DBE has been calculated to be ∼ 1 × 10⁶M^-1s^-1.     

ECE mechanism as a tool for the investigation of unstable metal complexes: Part I. Electrochemical reduction of trans-[CoBr2(N)4]+-type complexes on the mercury electrode

A polarographic investigation of trans-[CoBr₂(N)₄]⁺-type complexe where (N)₄ represents (NH₃)₄, (ethylenediamine)₂ and (propylenediamine)₂, has been carried out in acetate buffer solutions. These complexes gave two polarographic waves; the first wave corresponds to the reduction of Co(III) to Co(II) and the second to the reduction of Co(II) to Co(0). The relation between current and time of the first wave in a positive potential is dependent on the dissolution wave due to bromide ions produced by acid hydrolysis and parallel ECE mechanism. Overall reaction is as follows: at the electrode surface, [Co(III)Br₂(N)₄]⁺+e^-→[Co(II)Br₂(N)₄] [Co(II)Br₂(N)₄]+6H₂O→[Co(II)(H₂O₆]²⁺+2Br^-+(N)₄ 2Br^-+2Hg→Hg₂Br₂+2e and in the solution, [Co(III)Br₂(N)₄]⁺+2H₂O→[Co(III)(H₂O₂(N)₄]³⁺+2Br^-The effects of the acid hydrolysis of a tervalent cobalt complex on the current—potential curve were simulated.     

Br-掺杂Bi2WO6的水热法合成及其可见光催化性能

以Bi（NO₃）₃·5H₂O和Na₂WO₄·2H₂O为主要原料,采用水热法合成了纯相Bi₂WO₆,并对其进行非金属离子Br^-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br^-掺杂对Bi₂WO₆的物相结构、形貌和可见光催化性能的影响。结果表明,Br^-掺杂可有效提高Bi₂WO₆的可见光催化性能,当掺杂量（物质的量百分数）为8%时,溴掺杂Bi₂WO₆的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi₂WO₆相比,其降解率提高了36.32%。     

Br~-掺杂Bi_2WO_6的水热法合成及其可见光催化性能

以Bi(NO_3)_3·5H_2O和Na_2WO_4·2H_2O为主要原料,采用水热法合成了纯相Bi_2WO_6,并对其进行非金属离子Br-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br~-掺杂对Bi_2WO_6的物相结构、形貌和可见光催化性能的影响。结果表明,Br-掺杂可有效提高Bi_2WO_6的可见光催化性能,当掺杂量(物质的量百分数)为8%时,溴掺杂Bi_2WO_6的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi_2WO_6相比,其降解率提高了36.32%。     

类微乳化学沉淀法合成BiOBr-TiO2纳米复合材料及其光催化性能

采用简单的类微乳化学沉淀法获得了有效复合的BiOBr-TiO2纳米材料.该合成方法的关键在于Br-的双重作用.Br-既作为"桥"将十六烷基三甲基溴化铵(CTAB)中CTA+与TiO2粒子相连,构筑了稳定的油包水的类微乳体系.同时,它又作为BiOBr的溴源有助于纳米复合材料异质结的形成.与纯TiO2和传统的水相化学沉淀法获得的BiOBr-TiO2复合样品相比,采用类微乳化学沉淀法获得的复合光催化剂表现出高的光生电荷分离效率,相应地显示出优异的光催化降解气相乙醛和液相苯酚的性能,这主要与BiOBr和TiO2粒子之间异质结的有效构筑有关.     

Selective photometric determination of low conentrations of selenium(IV) and selenium(VI) in bottled drinking water

A procedure is developed for the selective photometric determination of selenium(IV) in bottled drinking water by the oxidation of Methylene Blue in 1 M HCl to colorless decomposition products and of selenium(VI) by its interaction with the specified reagent at pH 5–6 with the formation of a colored ion pair. The limits of detection are 1 and 0.8 µg/L, respectively. At the concentration of selenium(IV) 2 µg/L, the admissible weight ratios are: SeO₄^2-, Br₃^- (1: 20); Br^– (1: 60); I^–, IO₃^- and IO₄^- (1: 100). At equal concentration of selenium(VI), the following species: SeO₄^2-(1: 20); Br₃^-, Br^–, I^–, IO₃^-, and IO₄^- (1: 100) do not interfere with the determination. Other anions and cations present in highly mineralized waters do not interfere with the determination. The relative error of determination is 8–10% in the concentration range 2–10 µg/L of selenium(IV) and selenium(VI) and does not exceed 5% in their concentration range of 10–100 µg/L.     

Change in Volume Properties of and Complex Formation in the System Hg(NO3)2-KX-H2O (X- = Cl-, Br-, I-)

The chemical nature of the anions in step complex formation in Hg(NO₃)₂-KX-H₂O systems (X^- = Cl^-, Br^-, I^-) manifests itself in different trends in variation of the molar volumes of the solutions.     

Further improvements in the 2,4-xylenol spectrophotometric method for nitrate

Improvements are described for the 2,4-xylenol spectrophotometric method for nitrate that reduce the elapsed and working time. Diluted (22 + 3) sulfuric acid is added quickly to the sample solution while the flask is immersed in tap water. 2,4-xylenol solution is added, the 6-nitro-2,4-xylenol formed is steam-distilled into a composite ammonia—isopropanol reagent, and the absorbance of the ammonium salt of 6-nitro-2,4-xylenol is measured. Further possible interferences are described. Br₂, I₂, ClO^-, CIO₃^-, BrO₃^-, and I0₄^-, cause low results by deactivating or destroying the 2,4-xylenol. Azide, hydrazine, and elemental carbon cause low results by reducing the nitrate in the strong sulfuric acid solution. Se⁺ causes low results because 2,4-xylenol is consumed in reducing Se⁴⁺ to the element. Pt⁴⁺ and Os⁸⁺ cause high results. Interferences from Br₂, I₂, ClO^-, ClO₃^- lO₃^-, and I0₄^- can be eliminated by reduction to the halide with sulfurous acid and precipitation with silver sulfate. Sulfurous acid reduction also eliminates interferences from V⁵⁺. Mn⁷⁺, Cr⁶⁺, S₂O₈^2-, and H₂0₂. Interferences from N₃^-, Br₂, I₂, and S₂0₈^2- are eliminated merely by boiling a 0.5% sulfuric acid solution for 30 min (and precipitating any residual halide with silver sulfate).