单柱离子色谱法测定钼酸根和钨酸根离子的研究

本文采有单柱离子色谱系统测定了MoO_4~(2-)和WO_4~(2-)。以1.0mmol/L钼酸钠为淋洗液测定WO_4~(2-),以1.0mmol/L钨酸钠为淋洗液测定MoO_4~(2-),常见阴离子Cl~-、NO_3~-、SO_4~(2-)不干扰测定,MoO_4~(2-)和MO_4~(2-)的检出限分别为3.55μg/ml和5.03μg/ml,相对标准偏差为1.04％和1.66％,工作曲线的线性范围为3.55～1500μg/ml和5.03～1500μg/ml。应用于钼、钨、硅杂多酸中钼和钨的测定,结果满意。     

WO_4~(2-)掺杂SrMoO_4:Eu,Li红色荧光粉的制备与发光性能研究

在SrMoO_4:Eu,Li中引入WO_4~(2-),采用预先球磨、再热处理的高温固相合成法制备了白光LED用红色荧光粉Sr(MoO_4)_(1-x)(WO_4)_x:Eu,Li,利用XRD,分子荧光光谱仪等对其进行了研究。XRD分析表明,钨酸盐的引入没有改变SrMoO_4:Eu,Li的物相结构;荧光光谱测试发现,该荧光粉能有效地被396和466 nm激发,其主发射峰值位于615 nm(Eu~(3+)离子的~5D_0→~7F_2跃迁)的红光,且钨酸盐的引入不改变样品的激发光谱和发射光谱,加强了其发光强度。此外,文章还详细探讨了烧结温度对该体系荧光粉发光性能的影响。     

单斜相WO_3的水热合成及其光催化性能的研究

利用水热合成法,以钨酸钠为钨源,硝酸为酸源,柠檬酸与酒石酸为辅助剂,制备了单斜相且形貌规整的WO_3。对WO_3样品进行了X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)及紫外可见漫反射(UV-vis-DR)分析,测试了样品的BET比表面积,考察了硝酸与钨原子物质的量比,柠檬酸、酒石酸与钨原子物质的量比对样品晶相与形貌的影响。结果表明,大量硝酸及羟基酸的加入都有利于WO_3单斜相的形成,当硝酸与钨原子的物质的量比为2.8∶1,羟基酸与钨原子的物质的量比为0.8∶1时,能够制得单斜相、形貌规整的WO_3样品。将WO_3与p型半导体物质CuCrO_2复合得到CuCrO_2-WO_3复合催化剂用于光催化分解水产氢的实验,高结晶度的单斜相WO_3具有较好的光催化性能。     

负载氧化钨催化剂的拉曼光谱和程序升温还原研究

应用LRS、XRD、UV-DRS和TPR技术对负载氧化钨催化剂进行了表征.实验结果表明,WO_3在γ-Al_2O_3、TiO_2、SnO_2和ZrO_2载体表面高度分散直至形成完全覆盖单层;但在SiO_2表面WO_3难以分散.拉曼光谱是鉴别表面分散态和晶相WO_3的有力手段.对WO_3在表面单层覆盖的样品,表征表面 钨氧物种的拉曼振动频率的高低因载体而异.载体使表面钨氧物种稳定,抑制其还原并改变其还原进程.钨氧物种在载体表面的配位状态取决于负载量和载体的结晶结构.表面钨氧物种的拉曼频率和TPR还原峰温的高低与WO_3和载体之间相互作用的强弱有关.     

V2O5-MoO3体系的电子探针分析

V_2O_5—MoO_3体系是重要的氧化催化剂体系之一.许多作者分别用X射线衍射对V_2O_5—MoO_3体系进行了物相分析,测定了有关的晶体结构,用热分析或熔点显微镜研究其相图等.据文献报道,V_2O_5—MoO_3体系中当MoO_3含量低于约40mol％时,可形成MoO_3在V_2O_5中的固溶体相;当 MoO_3含量在约50mol％或稍高时,可形成中间化合物相;当MoO_3含量更高时,则以MoO_3相为主.但是,文献中对于V—Mo—O中间化合物相的化学组成的认识存在着分岐,有些作者归结为V_2MoO_8,另一些作者则归结为V_9Mo_6O_(40).这两种分子式表示法的差异首先在于V和Mo的原子比不     

CaO固硫过程中Ca~(2+)在CaSO_4产物层内扩散的研究

应用标记实验技术，研究CaO固硫反应过程中产物层扩散控制阶段的反应机理 。利用扫描电镜和反射式光学显微镜，对压制烧结并带有Pt标记的CaO样品在固硫 反应前后的形貌变化观察，结果表明：经过较长时间的固硫反应后，在Pt标记层外 表面形成一层覆盖物，XRD分析结果证明该覆盖物是CaSO_4。利用电化学综合测试 仪测量了CaO及CaSO_4在高温下的电导率，结果表明在1000 ℃时CaSO_4的电导率达 到了10~(-3)数量级，说明在高温下CaSO_4内Ca~(2+)有较高的离子迁移特性。根据 标记实验、电导率测试的结果和CaO掺杂体系的固硫动力学数据的分析认为：CaO固 硫反应在后期的扩散层控制阶段的主要反应是Ca~(2+)通过CaSO_4产物层扩散至 CaSO_4外表面与SO_2和O_2进行反应，生成CaSO_4，而不是SO_2和O_2气体通过 CaSO_4产物层向内扩散，在颗粒内部与CaO发生固硫反应。     

WO3/钛铝胶体系的表面结构

WO_3/钛铝胶系列样品通过浸渍法制备. XRD 和XPS 测定结果表明WO_3单层分散在钛铝胶表面, 分散阈值为0.22 g WO_3/(100 m~2). 假定WO_3在钛铝胶表面按照密置单层模型分散, 其计算值为0.198 g WO_3/(100 m~2). 表明测定值与理论模型的计算值相接近. LRS测定表明: 当WO_3的载量低于0.082 g WO_3/(100 m~2钛铝胶)时, 只有四而体配位的钨存在; 当WO_3的载量超过0.082 g WO_3/(100 m~2钛铝胶)时, 钨主要以八面体配位存在. 同时, LRS的实验结果也表明, 550 ℃焙烧的WO_3/钛铝胶样品没有Al_2(WO_4)_3生成. 对高温焙烧条件下, Al_2(WO_4)_3的生成也进行了研究.     

多功能Na_2WO_(4-)离子液体催化体系催化环己醇一锅合成己内酰胺（英文）

己内酰胺是合成尼龙-6和工程塑料的关键中间体.工业上己内酰胺的合成工艺分三步:以环己醇为原料合成环己酮,环己酮氨肟化合成环己酮肟,环己酮肟重排生成己内酰胺.该工艺存在工艺流程长、重排过程中使用发烟硫酸腐蚀设备、形成大量低值副产物硫酸铵等问题.随着人们对环境保护意识的提高,发展环境友好、经济效益高的直接合成己内酰胺工艺已经迫在眉睫.多步串联反应具有设备投资少、中间分离步骤少、反应效率高等优点,其关键问题之一是多功能催化剂的开发.环己醇作为环己烷氧化反应的副产物,能够直接用于己内酰胺的合成,具有理论研究价值和工业应用意义.本文构建了以环己醇氧化、环己酮肟化和环己酮肟重排反应构成的串联反应系统,可缩短己内酰胺合成工艺流程,降低能耗,减小环境污染.合成了九种离子液体,并与Na_2WO_4组成催化体系,以环己醇、过氧化氢和羟胺为原料,催化环己醇直接合成己内酰胺.首先研究了不同Na_2WO_(4-)离子液体催化体系对环己醇直接氧化合成环己酮反应的影响.反应介质的酸性和离子液体水油两相中的相转移功能是影响氧化过程的两个主要因素.Na_2WO_(4-)磺酸基功能化的离子液体催化剂具有较高的氧化活性.这是由于磺酸基的引入提高了催化剂酸性,另外磺酸基功能化的离子液体随碳链的增长,催化剂的亲油性增强,即该催化剂相转移功能增强.考察了九种离子液体对氧化过程的影响,其中Na_2WO_(4-)[BSTma]HSO_4在氧化过程中催化活性最高,因此将其用于催化环己酮与羟胺合成己内酰胺的反应,并考察了环己酮与[BSTma]HSO_4的摩尔比对该反应的影响,发现该摩尔比为1:0.08时,反应效果最好.最后,将Na_2WO_(4-)[BSTma]HSO_4体系用于催化环己醇直接合成己内酰胺的反应.考察了反应温度、反应时间和环己醇与[BSTma]HSO_4摩尔比的影响.在氧化时间为300 min,肟化和重排时间为150 min,反应温度为80 ℃,环己醇:H_2O_2:(NH2OH)2·H_2SO_4:Na_2WO_4·2H_2O:[BSTma]HSO_4的摩尔比为1.00:1.50:0.50:0.06:0.08的条件下反应效果最好,环己醇转化率为97.3%,己内酰胺收率为76.0%.Na_2WO_(4-)[BSTma]HSO_4催化体系活性较高的原因是离子液体阳离子的相转移作用,以及在氧化过程中离子液体与过氧钨酸盐的配位作用和对Beckmann重排过程中中间产物的稳定作用.研究了Na_2WO_(4-)[BSTma]HSO_4催化体系的普适性,发现该催化体系对所考察的脂肪醇和芳香醇直接合成酰胺均具有较好的催化活性.另外,回用的Na_2WO_(4-)[BSTma]HSO_4催化剂仍具有较好的催化活性.因此,该催化体系具有高效易回收、操作简单和反应条件温和的优点.     

CaO固硫过程中Ca~(2+)在CaSO_4产物层内扩散的研究

应用标记实验技术 ,研究CaO固硫反应过程中产物层扩散控制阶段的反应机理 .利用扫描电镜和反射式光学显微镜 ,对压制烧结并带有Pt标记的CaO样品在固硫反应前后的形貌变化观察 ,结果表明 :经过较长时间的固硫反应后 ,在Pt标记层外表面形成一层覆盖物 ,XRD分析结果证明该覆盖物是CaSO4.利用电化学综合测试仪测量了CaO及CaSO4在高温下的电导率 ,结果表明在 10 0 0℃时CaSO4的电导率达到了 10 -3 数量级 ,说明在高温下CaSO4内Ca2 + 有较高的离子迁移特性 .根据标记实验、电导率测试的结果和CaO掺杂体系的固硫动力学数据的分析认为 :CaO固硫反应在后期的扩散层控制阶段的主要反应是Ca2 + 通过CaSO4产物层扩散至CaSO4外表面与SO2 和O2 进行反应 ,生成CaSO4,而不是SO2 和O2 气体通过CaSO4产物层向内扩散 ,在颗粒内部与CaO发生固硫反应 .     

Bi2WO6量子点(QDs)修饰Bi2MoO6-xF2x异质结的构筑及其催化活性增强机理

采用简单沉积-沉淀法合成了Bi_2WO_6@Bi_2MoO_(6-x)F_(2x)(BWO/BMO_(6-x)F_(2x))异质结,借助XRD、XPS、TEM、SEM、EDS、UV-Vis-DRS、PC和EIS等测试技术对其组成、形貌、光吸收特性和光电化学性能等进行系统表征,并以模型污染物罗丹明B(Rh B)的光催化降解作为探针反应来评价Bi_2WO_6@Bi_2MoO_(6-x)F_(2x)异质结的光催化活性增强机制。形貌分析表明,所得Bi_2MoO_6微球由大量厚度为20~50 nm的纳米片组成;FE-SEM和HR-TEM分析表明,尺寸约为10 nm的Bi_2WO_6量子点均匀沉积在Bi_2MoO_(6-x)F_(2x)微球表面,形成新颖的Bi_2WO_6@Bi_2MoO_(6-x)F_(2x)异质结;与纯Bi_2MoO_6或者Bi_2WO_6相比,1∶1Bi_2WO_6@Bi_2MoO_(6-x)F_(2x)异质结表现出更好的光催化活性和光电流性质,其对RhB光催化降解的表观速率常数分别为纯BMO和BWO的6.4和11.6倍。PC和EIS图谱分析表明,Bi_2WO_6量子点表面沉积显著提高Bi_2MoO_(6-x)F_(2x)光生电子/空穴的分离效率和迁移速率;活性物种捕获实验证明了·O_2~-和h~+是主要的活性物种。根据实验结果,探讨了F-掺杂和Bi_2WO_6量子点之间的协同效应对Bi_2MoO_6的光催化活性的影响机制。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.