催化动力学光度法测定痕量钒的研究

研究了在 0 .0 1mol·L- 1硫酸介质中 ,痕量V(Ⅴ )催化溴酸钾氧化酸性络蓝K的褪色反应 ,建立了一种高灵敏度测定痕量V(Ⅴ )的新方法。方法的线性范围为 4～ 2 0ng·ml- 1,检出限为 1 0×10 - 9g·ml- 1。方法用于各种水样中痕量钒的测定 ,并进行回收试验 ,结果满意     

二安替比林对乙氧基苯基甲烷吸光光度法测定微量V(Ⅴ)

合成了新试剂二安替比林对乙氧基苯基甲烷,并研究了与V(Ⅴ)的显色反应。在磷酸介质中和Mn(Ⅱ)-乳化剂OP的作用下,显色反应的产物为橙黄色,ε为2.90×10~6,λ_(max)=450nm,测定V(Ⅴ)的线性范围为4～32μg·L~(-1)。用于中草药中微量V(Ⅴ)的测定,结果满意。     

石煤渣中痕量铌的高灵敏光度法测定

1引言利用Nb（Ⅴ）-SCN-RhB-PVA高灵敏显色体系。在聚乙烯酸（PVA）存在下,铌（Ⅴ）与疏氰酸盐形成配阴离子再和罗丹明B（RhB）形成较稳定的离子缔合物,可用光度祛在水相中直接测定铌（Ⅴ）。通过试验,确立了体系反应的最佳条件,在PVA介质中,离子缔合物的λmax=565nm,ε＝7．9×105·mol－1·cm－1,铌（Ⅴ）量在0－0．2mg／L范围内服从比耳定律。本法用于测定石煤渣中痕量铌,获得了满意结果。2实验部分2．1仪器和试剂721型分光光度计（上海第三分析仪器厂）;pffe3型酸度计（上海第二分析仪器厂）;501型超级恒温器（上海实…     

催化动力学光度法测定石煤渣中痕量铌的研究

研究了在稀盐酸介质中 ,痕量铌 (Ⅴ )催化溴酸钾氧化氯磺酚S的褪色反应 ,建立了一种痕量铌的催化动力学光度分析新方法。方法的检测限为 3.1×1 0 - 3mg/L ,线性范围为 5 .0～ 1 5 0 μg/L ,方法已应用于测量石煤渣中痕量铌     

二安替比林对异丙氧基苯基甲烷与钒(V)显色反应及机理

合成了新试剂二安替比林对异丙氧基苯基甲烷(DApIM),研究了它和钒(Ⅴ)的显色反应及机理.在磷酸介质中,Mn(Ⅱ)和吐温-80存在下,V(Ⅴ)氧化DApIM生成黄色产物,λ_(max)=450nm,ε=4.71×10~6·L·mol~(-1)·cm~(-1),钒(Ⅴ)的含量在0～12μg/L内符合比尔定律.方法用于废渣和生物样品中钒的测定,结果满意.     

新显色剂6,8-二磺酸萘偶氮氯磺酚与铌(Ⅴ)显色反应的研究及应用

本文研究了新显色剂6,8-二磺酸萘偶氮氯磺酚与Nb(Ⅴ)的显色反应和测定条件。在酸度为0.6～3mol/L盐酸时。络合物的组成比为Nb(Ⅴ):R=1:3,摩尔吸光系数为4.42×10~4L·mol·L~(-1)·cm~(-1)。可不经分离直接测定钢铁试样中的铌。     

褪色光度法测定天然水体中痕量氟

痕量氟的光度法测定常用茜素氟蓝法和褪色光度法.我们发现痕量氟离子对钍(IV)与4-(H-酸偶氮)-1-苯基-3-甲基吡唑啉酮(HAPMP)在CTMAB介质中的显色反应具有强烈的褪色作用,据此建立了一种测定痕量氟的新方法.体系表观摩尔吸光系数ε=2.16×10~4L·mol~(-1)·cm~(-1).氟离子含量在40～400μg/L内符合比尔定律,方法用于水样中痕量氟的测定,结果令人满意.     

贵金属高灵敏显色反应的研究 (Ⅳ)钯(Ⅱ)-碘化钾-罗丹明 B-聚乙烯醇体系

金(Ⅲ)-碘化钾-罗丹明B(Rh-B)体系的显色反应在明胶和抗坏血酸(V_c)存在下形成水溶性离子缔合型络合物,摩尔吸光系数ε=2.3×10~5l·mol~(-1)·cm~(-1)。钯(Ⅱ)的类似体系的灵敏度与金(Ⅲ)相近。就钯(Ⅱ)来说,发现用聚乙烯醇(PVA)替换明胶则显色反应的灵敏度明显增高,其ε=6.5×10~5l·mol~(-1)·cm~(-1)。因此,本文详细研究了Pd~(2+)-KI-RhB-PVA体系的最佳显色条件,拟定了测定痕量钯的高灵敏分光光度法。     

新催化光度法测定痕量铜的研究

目前,关于光度法测定痕量铜的方法很多,其中应用催化光度法测定痕量铜也有报道.本文采用具有助发色基团的2,4-二硝基苯肼在氯酸钾的催化作用下,与变色酸偶合,然后与Cu(Ⅱ)配合显色,反应机理如下:(?)试验确定了反应最佳条件,配合物的表现摩尔吸光系数ε=2.43×10~5L·mol~(-1)·cm~(-1),铜量在1     

meso-四[3,5-二(三氟甲基)苯基]卟啉与镉的显色反应研究

研究了新合成显色剂meso 四 [3,5 二 (三氟甲基 )苯基 ]卟啉 [T( 3,5 DTFMP)P]光度法测定痕量镉 (Ⅱ )的方法与应用。试验表明 ,在pH 1 0 .6的缓冲液、Tween 80及邻菲口罗啉介质中 ,经沸水浴加热 7min ,显色反应完全 ,Cd(Ⅱ )量在 0～ 3μg/2 5mL范围内具有线性关系 ,表观摩尔吸光系数ε442 为 2 1 9× 1 0 5L·mol- 1 ·cm- 1 。显色体系不经掩蔽可直接测定烟草中的痕量Cd(Ⅱ) ,选择性较高     

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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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%).