高碘酸钾氧化中性红褪色催化动力学光度法测定痕量硒(Ⅳ)

基于3.2×10-4mol/LH2SO4介质中,痕量硒(Ⅳ)催化KIO4氧化中性红的褪色反应,建立了测定痕量硒(Ⅳ)的动力学光度法。在固定加热时间段(6min)后,于530nm处测定中性红的吸光度降低值监控反应速率。方法检出限为0.36μg/L,校准曲线的质量浓度线性范围为0～8.0μg/L。实验了酸度、反应物浓度、温度、反应时间、干扰离子等因素的影响。研究了反应的最佳条件,并测定了一些动力学参数,催化反应的表观活化能为81.60kJ/mol。11次重复测定0.1μg/25mL和0.2μg/25mLSe(Ⅳ)的相对标准偏差分别为2.1%和1.9%。方法用于食品和人发样品中痕量硒(Ⅳ)的测定,相对标准偏差为0.33%～3.8%,加标回收率为96.0%～103.0%。     

聚酰胺分离富集置换催化光度法测定痕量铊

研究了在 0 .15～ 0 .0 8mol/L的硫酸介质中 ,用铊 置换出Cu EDTA中的Cu ;Cu 催化溴酸钾氧化偶氮氯瞵 mA褪色的指示反应及其动力学条件 ,据此建立测定痕量铊 的新方法。在 5 5 0nm处 ,检出限为 1.32× 10 -9g/L ;测定范围为 0～ 6 0 0 μg/L ,用聚酰胺在盐酸或王水介质中分离富集样品中的铊 ,使方法的选择性大大提高。用于水及岩石样品中铊的测定 ,相对标准偏差小于 3.7% ;标准加入回收率 96 %～10 4 % ,获得满意结果。     

超支化聚合物分离富集催化光度法测定痕量硒

研究了超支化聚合物在硝酸介质中分离富集硒,吸附的容量大,选择性高,无污染。同时研究了分离后硒在硝酸介质中,痕量硒(Ⅳ)催化溴酸钾氧化2',4'-二氯苯基荧光酮褪色的指示反应及其动力学条件,据此建立测定痕量硒(Ⅳ)的新方法,方法的检出限为4.21×108g·L1,测定范围为0-0.6μg/10mL,用于样品的测定获得满意结果。     

阻抑催化褪色光度法测定痕量绿原酸

在盐酸介质中 ,绿原酸能灵敏地阻抑铁 催化过氧化氢还原亮绿SF的褪色指示反应 ,据此建立了测定痕量绿原酸的阻抑 催化动力学光度分析方法。该方法测定绿原酸的线性范围为 0～ 0 .12mg/L ;检出限为4 .2× 10 -6g/L。对浓度为 0 .0 8mg/L绿原酸标准溶液 6次平行测定的相对标准偏差为 3.8% ;回收率为 93.4 %～ 10 5 %。考察了反应的最佳条件和动力学参数 ,探讨了反应机理。该方法应用于金银花浸取液中绿原酸含量的测定 ,结果满意     

催化动力学光度法测定大花红景天中的硒(Ⅳ)

建立了测定大花红景天中硒的一种新的催化动力学光度法.在酸性介质中,硒(Ⅳ)能催化H2O2氧化溴酚蓝-丁基罗丹明B的褪色反应,硒(Ⅳ)含量在0～5 μg/L范围内与褪色反应速率成正比.样品经HNO3-HClO4消化后直接测定硒(Ⅳ)的含量,该方法具有良好的选择性和准确度.用于大花红景天中硒的测定.     

二溴羧基偶氮胂催化动力学光度法测定痕量锡

基于稀H2SO4介质中,痕量锡（Ⅳ）催化KBrO3氧化二溴羧基偶氮胂（DBCAA）的褪色反应,建立了测定痕量锡（Ⅳ）的催化动力学光度法。方法检出限为0．23μg／L,线性范围为0．0～8．0μg／L。结合巯基葡聚糖凝胶（SDG）分离富集,可用于测定环境水样、人发及岩石样品中的痕量锡（Ⅳ）。     

巯基葡聚糖凝胶分离富集催化动力学光度法测定痕量锡(Ⅳ)

研究在稀硫酸介质中,以锡(Ⅳ)催化溴酸钾氧化铍试剂Ⅰ的褪色反应及其动力学条件,测定锡(Ⅳ)的范围为0～40μg/L:检测限为1.63×10-8g/L.采用巯基葡聚糖凝胶(SDG)分离富集,使方法的选择性得到了大大的提高,可用于多种样品中痕量锡(Ⅳ)的测定,结果令人满意.     

氧化偶氮胂M褪色光度法测定痕量钛(Ⅳ)

基于0．08mol／L的H2SO4介质中,痕量钛(Ⅳ)催化KBrO3氧化偶氮胂M的褪色反应,建立了测定痕量钛的催化光度法。方法检出限为0．26μg/L,线性范围为0～8．0μg/L。结合溶剂萃取分离技术,可用于人发、茶叶样品中痕量钛(Ⅳ)的测定。     

催化动力学光度法测定富硒茶叶中痕量硒

本文研究了Se催化过氧化氢氧化甲基橙反应体系测定痕量Se的方法。硒浓度在0～65．7μg／L范围内与褪色反应率lg(A0／A)呈线性关系。方法检出限为0．76μg／L。用于茶叶中硒的测定，结果较满意。     

催化动力学测定痕量对苯二酚

研究了在pH7.3的KH2PO4 Na2HPO4缓冲介质中,痕量对苯二酚催化高碘酸钾氧化靛红褪色的新指示反应及其动力学条件,建立了动力学光度法测定痕量对苯二酚的新方法。该方法检出限为6.8×10-6g L,线性范围是0.04～0 18μg mL和0.28～0.54μg mL。可用于显影废液中对苯二酚的测定。     

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%.     

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.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.