N,N-二甲基苯胺-对氨基二甲替苯胺氧化偶联反应催化分光光度法测定铬(Ⅵ)

在pH=3.2乙酸-乙酸钠缓冲介质中,研究了铬(Ⅵ)催化过氧化氢氧化对-氨基二甲替苯胺盐酸盐和N,N-二甲基苯胺的氧化偶联反应及其机理,建立了催化光度法测定痕量铬(Ⅵ)的新方法.该方法线性范围为0～0.12 mg/L;检出限为1.0×10-7 g/L;相对标准偏差为0.12%,直接用于水中铬(Ⅵ)的测定,结果满意.     

1,2-萘醌-4-磺酸钠体系分光光度法测定磺胺甲噁唑

采用1,2-萘醌-4-磺酸钠体系分光光度法测定磺胺甲噁唑(SMZ)。磺胺甲噁唑与1,2-萘醌-4-磺酸钠在pH=10.0的缓冲溶液中发生亲核取代反应生成橙红色的产物,组成比为1:1,最大吸收波长λ=476 nm;表观摩尔吸光系数ε=6.44×103L/(mol.cm);SMZ浓度在0.2~60 mg/L范围内呈良好的线性关系;线性回归方程为A=0.02452 0.02301C(mg/L),线性相关系数r=0.9991;检出限为0.08 mg/L;RSD为0.25%(20 mg/L,n=11);平均回收率为98.7%以上。优化了对磺胺甲噁唑的测定条件。初步探讨了反应机理,应用拟定的方法测定磺胺甲噁唑的含量,与药典法相比,结果满意。     

1, 2-萘醌-4-磺酸钠分光光度法测定间苯二酚

在pH 13.00缓冲溶液中, 间苯二酚能够催化氢氧根离子与1,2-萘醌-4-磺酸钠反应生成2-羟基-1, 4-萘醌, 其最大吸收波长为454 nm. 间苯二酚质量浓度在0.39～13.21 mg/L范围内与吸光度呈现良好线性关系. 线性回归方程为A=0.01918+0.05703c (×105 mol/L), 相关系数r=0.9981. RSD和检测限分别为1.6%, 0.34 mg/L (3σ/k). 该法能够直接用于水样中间苯二酚含量测定, 回收率在94.3%～106%.     

2-(2-喹啉偶氮)-4-甲基-1, 5-苯二酚测定银的研究

合成了新试剂2-(2-喹啉偶氮)-4-甲基-1,5-苯二酚(QAMDHB),研究了其与银的显色反应.在pH=4.7的乙酸-乙酸钠缓冲介质中,QAMDHB与银反应生成2∶1的稳定络合物,λmax=558 nm,ε=5.8×104 L*mol-1*cm-1,银含量在0～1.6 mg/L内符合比耳定律.方法用于环境废水中银含量的测定,结果满意.     

钒酸铵氧化-分光光度法测定盐酸氯丙嗪

在磷酸介质中,钒酸铵与盐酸氯丙嗪反应生成红色氧化产物,其最大吸收波长为524nm;据此建立了测定盐酸氯丙嗪含量的钒酸铵氧化-分光光度法,并将其用于直接测定药物制剂中的盐酸氯丙嗪.结果表明,当盐酸氯丙嗪的浓度处于10.0～100mg/L和100～360mg/L范围内时,被测定体系的吸光度与盐酸氯丙嗪的浓度之间呈良好的线性关系;线性回归方程分别为A=-0.061 69+0.010 05c(mg/L,r=0.998 8)、A=0.494+0.004 43c(mg/L,r=0.998 8),检出限为1.96mg/L,相对标准偏差为0.29%,回收率为94.9%～102.9%.     

β-环糊精构筑模拟酶催化法测定葡萄糖

采用β-环糊精（β-cyclodextrin,β-CD）二间羧基苯磺酸酯同三氯化铁构筑模拟酶催化法,对葡萄糖制剂中的葡萄糖进行测定并寻找最佳测定检测条件。方法简例,灵敏度和重现性理想,线性范围120-400mg/L,检测下限为60mg/L,精密度试验RSD为1.9%(n=8）。     

痕量银的催化动力学—离子选择电极法测定

1 引言 催化动力学分光光度法测定痕量银已有很多报道,但应用催化动力学-离子选择电极法测定尚属少见。本文利用下列指示反应:选用0.02mol/LCe(Ⅳ)-4×10~(-5)mol/L KCl-0.02mol/L H_2SO_4体系,采用氯离子选择电极作监测器,进行了痕量银的催化动力学-离子选择电极法测定。试验证明,本方法仪器简单,操作方便,线性范围为0～0.8μg/50ml,检出限量为5×10~(-4)μg/ml,用于矿物标样分析,取得令人满意结果。     

2-甲基-1-(4-芳基噻唑-2-基)-苯并咪唑-6-甲酸乙酯的合成、表征及生物活性

以4-乙酰氨基苯甲酸乙酯为原料设计合成了14 种2-甲基-1-(4-芳基噻唑-2-基)-苯并咪唑-6-甲酸乙酯新化合物. 化合物结构经质谱、1H NMR、红外光谱和元素分析等确证, 并用单晶X射线衍射仪测定了化合物5a的晶体结构. 生物活性实验结果表明, 化合物5c(500 mg/L)对小麦白粉病菌抑制率达到95%; 化合物5e对辣椒疫霉病菌(25 mg/L)的抑制率为61.9%, 对油菜菌核病菌(500 mg/L) 抑制率高达97.2%; 化合物5k(25 mg/L) 对小麦赤霉病菌抑制率为55.1%.     

过氧化氢-2,4-二氯苯酚-4-氨基安替比林体系催化光度法测定血红细胞中的铁

基于在十二烷基硫酸钠存在下的弱碱性介质中Fe(Ⅲ)对H_2O_2氧化2,4-二氯苯酚(2,4-DCP)与4-氨基安替比林(4-AAP)偶联显色反应的催化作用,建立了检出限为7.90μg/L.线性范围为0～1.25mg/L的新催化光度分析法.方法用于血红细胞中铁的测定,相对标准偏差与回收率分别为2.6%与98.8%～101%,结果满意.     

萃取动力学光度法测定活化剂铝——铝(Ⅲ)-过氧化氢-铜(Ⅱ)-邻氨基酚/氯仿体系

研究了在pH 5.5的弱酸性介质中, 利用Al(Ⅲ)对Cu(Ⅱ)催化H2O2氧化邻氨基酚显色的指示反应的活化作用.用萃取平衡控制反应时间、水相中邻氨基酚的浓度和反应进行的程度.通过在424 nm下测量有机相的吸光度,建立了萃取催化光度法测定活化剂铝的新方法.方法的线性范围为0.004～0.25 mg/L,检出限为1.6×10 -6 g/L.用于水样和茶叶中铝含量的测定,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.     

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.