表面活性剂增敏阻抑动力学光度法测定痕量草酸

在稀盐酸介质中，微量草酸对H2O2氧化靛红的褪色反应有显著的阻抑作用，非离子表面活性剂Triton X-100对此体系有强烈的增敏作用，据此建立了表面活性剂增敏阻抑动力学光度分析测定微量草酸的新方法。方法的线性范围是0．005-0．50mg/L，检出限为0．005mg/L。方法简便，快速，灵敏度高，用于菠菜和尿样中草酸含量的测定，结果满意。     

阻抑动力学光度法测定废水中的痕量对苯二胺

在硫酸介质中,对苯二胺能灵敏地阻抑Cu（Ⅱ）催化高碘酸钾氧化孔雀绿的褪色反应。研究了该阻抑褪色反应的最佳条件,并据此建立了测定痕量对苯二胺的阻抑催化动力学光度分析方法,对苯二胺的线性范围为0．6～4．0mg／L,检出限为0．33mg／L。将该方法应用于模拟废水中对苯二胺含量的测定,测定结果的相对标准偏差为2．1％～2,3％,对苯二胺的加标回收率为99％-103％。     

阻抑-催化褪色动力学光度法测定食盐中的微量碘

在KH2PO4-K2HPO4介质中,微量碘(I-)对过氧化氢氧化碱性藏花红褪色反应有抑制作用,据此,建立了阻抑催化褪色动力学光度测定痕量碘的方法。该法的线性范围为0~40μg/L,检出限为1.6×10-8g/L。本法用于食盐中微量碘的测定,分析结果满意。     

Sm(Ⅲ)-KBrO3-瑞士色素体系阻抑动力学光度法测定微量钐(Ⅲ)

研究发现在稀HCl介质中,微量钐(Ⅲ)对溴酸钾氧化瑞士色素褪色反应有很好的阻抑作用。据此建立了阻抑动力学光度法测定微量钐(Ⅲ)的新方法。确定了反应的最佳条件,并讨论了动力学参数。方法线性范围为0.0~0.32mg/L,检出限为6.47×10-6g/L。     

阻抑动力学分光光度及荧光光度法测定微量碘

在稀磷酸介质中,微量碘离子对亚硝酸根催化溴酸钾氧化吡罗红B褪色及荧光猝灭的反应有显著阻抑作用,以此为指示反应提出了测定微量碘离子的阻抑动力学光度和阻抑动力学荧光分析新方法。测定碘离子的线性范围分别为4-200μg/L和3-40μg/L,检出限分别为2.8μg/L和1.6μg/L。用于食品中微量碘的测定,结果满意。     

阻抑催化光度法测定茶叶中的微量氟化物

在氨基乙酸 HCl缓冲溶液中 ,Fe3+对H2 O2 氧化 2 ,4 二氨基苯酚 (DAP)褪色具有催化作用 ,游离F- 离子与Fe3+形成的稳定络离子 [FeF6]3- 可抑制褪色 ,抑制程度与F- 量线性相关。基于此建立了测定微量F- 的阻抑催化光度分析的新方法。结果表明 ,有色溶液的最大吸收波长为 5 0 0nm ,测定的线性范围为 0～ 9.0mg/L ;摩尔吸光系数为 2 .1× 1 0 5L/mol/cm ;RSD(n =6)为 5 0 %。已应用于茶叶中微量F- 的测定     

胶束增敏阻抑动力学光度法测定痕量水杨酸

基于在H2SO4介质中,溴化十六烷基吡啶(CPB)对于KBrO3氧化曙红Y褪色反应的增敏作用和水杨酸对此反应的阻抑作用。建立了阻抑动力学光度法测定痕量水杨酸的新方法。研究了该反应的最适宜的条件和动力学参数。方法的表观摩尔吸光系数为3.79×105L.mol-1.cm-1,线性范围为:0.040~0.50mg/L,检出限为0.020 mg/L。方法用于复方苯甲酸搽剂中水杨酸的测定。对阻抑褪色反应的机理进行了探讨。     

阻抑动力学光度法测定白鼠肝脏中的超痕量镍(Ⅱ)

在 NH3- H2 O- NH4 Cl介质中 ,超痕量镍 ( )能阻抑 H2 O2 氧化甲基紫褪色的指示反应 ,研究了阻抑褪色反应的最佳条件和动力学参数 ,建立了测定超痕量镍 ( )的新方法。方法检出限为 4.4× 1 0 -11g/m L Ni( ) ,测定范围为 0～1 .0μg/2 5m L。方法已用于测定生物样品中的 Ni( )。     

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     

流动注射光度法测定矿井水中微量氟化物

研究了在pH2.76氨基乙酸－盐酸缓冲溶液中，Fe^3 对H2O2氧化2，4－二氨基苯酚（DAP）褪色具有催化作用。游离F^-离子与Fe^3 形成的稳定络合物可阻抑催化作用，阻抑程度与F^-量线性相关。基于此，将流动注射技术引入分析体系，建立了测定微量F^-的流动注射催化光度分析法。结果表明：λmax为500nm,F^-测定的线性范围为0.0-9.0mg/L;检出限为0．09mg/L;测定频率为90次／h；RSD＜5％（n=6).本法灵敏度高，选择性好，分析速度快，可用于测定矿井水和自来水中微量F^-.     

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%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.