苦胺酸偶氮变色酸光度法测定硝酸镍中痕量钴

研究了苦胺酸偶氮变色酸与钴显色反应的条件。在氨性条件下,试剂与钴发生显色反应,最大吸收波长为645nm,摩尔吸光系数为2.65×10~4L/(mol·cm),钴含量在0～ug/25mL内符合比尔定律。在以大量基体元素打底的情况下,不需另加任何其它掩蔽剂,可直接测定硝酸镍中的痕量钴。     

苦安酸偶氮变色酸褪色光度法测定硅铁中钙

在pH 11.0的氨水-NH4Cl介质中,研究了显色剂苦安酸偶氮变色酸与钙的褪色反应,建立了测定硅铁中钙的褪色光度分析方法.讨论了吸收光谱、酸度、试剂用量、干扰离子等因素的影响,确定了反应的最佳条件.在25 mL的溶液中,钙量在8～90 μg范围内符合比尔定律,该方法表观摩尔吸光系数为1.26×104 L·mol-1·cm-1,可用于硅铁中钙的测定.其RSD在1.4%～2.1%之间.     

苦安酸偶氮变色酸褪色光度法测定硅铁中的铁含量

基于pH 7.8的氨水-氯化铵介质中显色剂苦安酸偶氮变色酸与铁的褪色反应,建立了测定硅铁中铁含量的褪色光度分析方法.讨论了吸收光谱、酸度、显色剂用量、干扰离子等因素的影响,确定了反应的最佳条件.铁量在2～40 μg/(25 mL)范围内符合比耳定律,表观摩尔吸光系数为3.27×104 L·mol-1·cm-1.用该方法对硅铁标准样品中的铁进行测定,测定结果与标准值的相对误差低于0.3%,RSD为1.4 %～2.1 %(n=6).     

化学镀钴基合金镀液中钴的快速测定

研究了采用显色剂 苦胺酸偶氮变色酸对化学镀钴基合金镀液中钴含量进行测定的试验条件,在pH11的氨 氯化铵缓冲溶液中,钴与显色剂配合物的最大吸收峰在650nm波长处,钴(Ⅱ)在0～60μg/25ml范围内服从比耳定律,表观摩尔吸光系数为3.1×104L·mol-1·cm-1。该法测定钴的选择性好,在大量镍存在下,也能准确测定,对镀液样品进行了测定,相对标准偏差小于1%,结果满意。     

钒(Ⅴ)-2-(2-噻唑偶氮)-5-二甲氨基苯甲酸显色反应的研究

钒是具有重要用途的元素,其测定受到重视.二安替比林甲烷类[1]及杂环偶氮苯酚类显色剂[2,3]测定钒灵敏度和选择性较高,变色酸偶氮类显色剂[4-5]的应用也曾有报道,而杂环偶氮苯甲酸类显色剂研究较少[7,8].本文研究了钒(Ⅴ)与2-(2-噻唑偶氮)-5-二甲氨基苯甲酸(TAMB)的显色反应,结果表明,在pH 3.5～3.8甲酸-NaOH缓冲介质中,钒(Ⅴ)与TAMB反应生成一种稳定的可溶于水的蓝色配合物.     

2-(2-喹啉偶氮)-5-二乙氨基苯胺光度法测定钴

合成了新试剂 2 (2 喹啉偶氮 ) 5 二乙氨基苯胺 (QADEAA) ,并研究了其与钴的显色反应 ,在pH为5 .5的磷酸盐缓冲介质中 ,在CTMAB存在下 ,QADEAA与钴反应生成 2∶1稳定络合物 ;用磷酸酸化后 ,在酸介质中 ,体系λmax=6 2 5nm ,ε =1 .4 6× 1 0 5L·mol-1 ·cm-1 。钴含量在 0 .0 1～ 0 .30mg/L内符合比尔定律。方法用于大米、猪肝及水样中钴含量的测定 ,结果令人满意     

变色酸光度法测定甲醛的改进

建立了用变色酸光度法测定甲醛的方法。采用浓磷酸和过氧化氢混合体系取代原有方法中使用的具有危险性和腐蚀性的浓硫酸。在浓磷酸介质中,甲醛与变色酸反应生成紫红色化合物,于570 nm波长处作光度测定。在甲醛的质量浓度为0.8-4.8 mg.L-1范围内遵守比耳定律。线性相关系数为0.9933。应用于测定香菇中的甲醛,回收率为92.7%-105.3%。     

[(2-胂酸基苯基)偶氮]-8-氨基喹啉与钴的显色反应研究

在pH 7.8～ 9.5的硼砂缓冲溶液中 ,在CTMAB的存在下 ,钴 (Ⅱ )与新显色剂 (2 胂酸基苯基偶氮 ) 8 氨基喹啉 (o APAQ)反应生成蓝绿色络合物 ,在 610nm处有吸收峰。显色剂本身在此条件下的吸收峰位于 4 5 0nm处 ,对比度 (Δλ)达 160nm。显色反应须在 70～ 80℃的水浴中加热 10min完成 ,可稳定至少 12h ,对常见的共存离子作了干扰试验 ,将此反应用于维生素V12 注射液及废水中微量钴的光度测定。经试验测定的准确度和精密度较满意     

光度法测定锌钴镀液中钴

研究了显色剂二溴对甲偶氮二溴羧与钴(Ⅱ)的显色反应。在pH 10.2的柠檬酸铵-氨水缓冲溶液中,钴(Ⅱ)与二溴对甲偶氮二溴羧反应形成绿色配合物,最大吸收波长为650 nm,表观摩尔吸光率为2.59×104L.mol-1.cm-1。钴质量浓度在1.0 mg.L-1以内符合比耳定律。方法用于锌钴镀液中钴的直接测定,测得相对标准偏差(n=5)平均值为1.65%,平均回收率为100.5%。     

催化光度法测定粉煤灰中微量钍

在pH2．0的HNO3介质中,痕量钍㈣对过氧化氢氧化苦胺酸偶氮变色酸(PAACA)的褪色反应有强的催化作用。加入乳化剂OP能提高其灵敏度,催化程度与钍（Ⅳ）量线性相关。借此建立了测定痕量钍（Ⅳ）的分光光度法。结果表明：有色溶液的最大吸收波长为545nm;方法检出限为0．80μg/L;线性范围为4.0～120μg／L,钍（Ⅳ）的标准加入回收率在98．5％～103．6％之间。结合PMBP-甲苯萃取分离,用于测定粉煤灰中的微量钍,结果满意。     

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.     

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.     

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.     

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.